Terms and definitions for computed tomography of the kidneys. Anomalies and variants of kidney development Fetal lobulation

- a limited accumulation of pus in the cortex or medulla of the kidney. When computed tomography without contrast, it looks like a formation with unclear contours, containing a liquid component in the center, as well as gas bubbles (if infected with gas-forming flora). The pyogenic membrane has the property of being enhanced by contrast to a significant extent.

Kidney agenesis

- complete absence of the kidney, as well as the ureter, renal arteries and veins on one side.

Kidney adenoma

- a common finding during CT examinations of the retroperitoneal organs. When performing a computed tomography scan of the kidneys (with or without contrast), an adenoma cannot be clearly differentiated from renal cell carcinoma; it looks similar - in the form of a hypo- or hypervascularized node in the renal parenchyma, a heterogeneous - cystic-solid structure, enhancing with contrast.

Angiomyolipoma of the kidney

- a tumor consisting of adipose, muscle and vascular proliferative tissue. On a CT scan of the retroperitoneal space, it looks like a formation of heterogeneous density (areas of low density -20...-60 Hounsfield units against the background of strands of higher, soft tissue density), with uneven edges, deforming the contour of the kidney. Angiomyolipoma is the only kidney tumor whose benign nature can be confirmed without performing any other tests.

Angiomyolipoma of the kidney on computed tomography looks like a rounded formation with heterogeneous density due to the fact that it contains fat, muscle and vascular tissue in different proportions. In the example presented, the average density of the mass near the lower pole of the right kidney is -20 Hounsfield units.

Renal artery aneurysm

- local expansion of the lumen of the renal artery as a result of weakening and stretching of its wall. Diagnosed by CT angiography of the renal artery, the expansion of the lumen is clearly visible, in which blood clots can also be detected.

Kidney aplasia

- reduction in kidney volume and disruption of its normal structure. With aplasia in the kidney, the number of pyramids is less than normal, and the pyelocaliceal complex may have the appearance of an “onion.”

Ureteral atresia

- absence of lumen of the ureter, congenital pathology.

Vesico-ureteral reflux

- a condition in which there is a reverse flow of urine from the bladder into the ureter. This type of reflux can only be detected with retrograde cystography (with filling the bladder with contrast from the outside) by contrasting the distal parts of the ureters.

Kidney cortical substance

- a complex of structures containing renal vessels, tubules and glomeruli. On CT scan of the retroperitoneum, the renal cortex is isodense to the renal medulla; with contrast enhancement, it becomes hyperdense (due to greater vascularization).

On the axial scan, arrows indicate the renal cortex, which appears hyperdense in relation to the medulla in the arterial phase of contrast due to better vascularization.

Kidney medulla

- a structure consisting of renal pyramids separated from each other by the cortex (Bertini's columns). The apices of the pyramids, merging, form the renal papillae, which conduct urine into the pyelocaliceal system.

Bulging of the kidney contour

– with CT scan of the kidneys without contrast, the local area in which the contour of the kidney bulges outward is always suspicious of a tumor and requires contrast enhancement.

Local bulging of the contour of the left kidney on native CT. Suspicion of hypernephroma. A contrast-enhanced study is required.

Biscuit bud

- an anomaly characterized by complete fusion of both kidneys with the location of the formed biscuit-shaped kidney prevertebral (middle) or near the sacrum - in the pelvic cavity.

Kidney hematoma

- the result of a traumatic impact (most often - a blow with a blunt object in the lumbar region or a fall on the back), in which, as a result of the application of force, blood vessels rupture and blood comes out. Hemorrhages into the renal parenchyma appear on CT as hyperdense areas, the density of which remains approximately the same over a long period of time. Hematomas can be intraparenchymal, subcapsular; may also burrow into the urinary tract.

Hematuria

- a condition in which the hemorrhagic component is detected in the urine. A CT scan of the urinary system can reveal hyperdense blood clots in the bladder or in an enlarged ureter.

Hemorrhagic kidney cyst

- a high-density formation in the kidney (60-70 Hounsfield units), containing fresh or partially lysed blood. All hemorrhagic cysts belong to category 3 according to the Bosniak classification.

An example of a hemorrhagic cyst of the right kidney on computed tomography (marked with an arrow). Hemorrhagic kidney cyst is denser (60...65 Hounsfield units). In this case, the patient has polycytosis of the kidneys with the presence of cysts of various structures and densities.

Hydronephrosis

- a condition manifested by expansion of the renal pyelocaliceal complex on computed tomography as a result of obstruction or obstruction of the ureter due to urolithiasis, with tumors compressing the ureter from the outside.

Left-sided hydronephrosis on computed tomography of the kidneys is manifested by dilation of the renal pyelocalyceal complex. Nephrographic contrast phase.

Hydronephrotic sac

- a condition characterized by extremely pronounced expansion of the calyxes and renal pelvis, in which the medulla and cortex of the kidneys are visualized on computed tomography as a thin strip of tissue. The final stage of hydronephrosis.

Hydrocalyx

- expansion of only one group of calyces, a particular variant of hydronephrosis.

Hydroureter

An example of a sharp unilateral dilatation of the ureter due to obstruction of stones in the area of ​​the mouth is a right-sided hydroureter.

Left-sided hydroureter on axial sections on CT scan of the pelvis (in different patients).

Hypernephroma

— syn. renal cell carcinoma is a malignant kidney tumor of various histological structures (clear cell kidney cancer occurs with a frequency of up to 80%, papillary cell carcinoma with a frequency of 10-15%, chromophobe cell kidney cancer with a frequency of about 5%). Hypernephroma causes deformation of the contour of the kidney; before contrast, it looks like a solid node, isodense to the renal parenchyma, which may also contain calcifications and hemorrhages in the structure. In the arterial phase of contrasting, hypernephromas noticeably intensify due to their high vascularization, after which their heterogeneous structure becomes clearly visible - with the presence of solid and cystic components.

A classic example of hypernephroma on CT scan of the retroperitoneal space is in the form of a space-occupying formation in the upper parts of the left kidney, which has a heterogeneous structure due to different contrasts of the solid and fluid (cystic) components, as well as the presence of hemorrhages.

An example of renal cell carcinoma on CT scan of the kidneys without contrast, in the arterial, venous phases of contrast, as well as in the nephrographic phase.

Changes highly suspicious for hypernephroma on CT scan of the kidneys without contrast.

Hypertrophy of the renal columns

- a variant of kidney development in which thickened Bertini columns can imitate a tumor process.

Functional kidney hypertrophy

- a unilateral increase in the size of the organ that occurs in connection with nephrectomy. The remaining single kidney has a heavy burden of filtering blood, resulting in compensatory hypertrophy.

Glomerulonephritis

- in the acute stage of glomerulonephritis, computed tomography of the kidneys does not reveal any changes, in the chronic stage - atrophy of the renal cortex with an enlargement of the renal sinus can be detected.

Post-resection cortical defect

- a local area in which the cortex is absent, resulting from surgical treatment - marginal resection. With computed tomography of the kidneys, small post-resection defects are difficult to detect due to their filling with retroperitoneal fat.

Kidney dystopia

– location of the kidney in an atypical place, for example, in the pelvis or in the chest cavity (an extremely rare variant of dystopia is the intrathoracic kidney).

An example of pelvic dystopia of the kidney. Computed tomograms visualize a polycystic kidney with multiple large calcified stones, localized in the pelvic cavity presacral - near the sacrum.

Dystopia crossed with fusion

– an anomaly of kidney development, in which there is dystopia of one of the kidneys with its movement on one side of the spine and fusion with the other kidney. CT urography can reveal two ureters, one of which is located in a typical location, and the other crosses the midline and enters the bladder from the opposite side. A renal CT scan can show a single, large kidney on one side of the spine.

Dystopia cross without fusion

- a rare anomaly in which the kidneys do not fuse when one of them is dystopic. With CT, both kidneys are visualized on one side of the spine, however, they lie completely separate from each other and have a separate fat capsule.

Kidney infarction

- death of the renal parenchyma in a limited area (the size of which depends on the degree and level of occlusion of the arterial vessel), manifested on computed tomography of the retroperitoneal organs in the form of a lack of contrast in the area of ​​the renal parenchyma - most often wedge-shaped.

The lack of contrasting of the cortical substance of the right kidney in the middle and upper parts due to circulatory disorders in this area is an example of a renal infarction.

Calcified kidney stone

- the most commonly detected type of renal calculi, which is characterized by high (up to 1000 Hounsfield units) density.

Example of calcified kidney stones on CT scan.

An example of a high-density stone (calcification) in the renal pelvis.

Stone in the lower group of calyxes of the left kidney (calcification).

Xanthine kidney stone

Xanthine kidney stone

Subcapsular kidney cyst

- renal cyst localized under the capsule.

Cortical kidney cyst

- a cyst localized in the cortical layer of the kidney.

Kidney medullary cyst

-located in the renal medulla.

Examples of simple cysts of the right kidney, localized mainly in its medulla.

Parapelvic kidney cyst

- localized near the pyelocaliceal complex, can cause compression with impaired urine outflow (rarely).

A huge cyst of the sinus of the right kidney (parapelvical), causing severe compression and deformation of the renal pelvis and calyces, and also leading to disruption of the outflow of urine.

Echinococcal kidney cyst

- cystic kidney damage caused by echinococcus. On CT, renal echinococcosis manifests itself as the presence of cysts with clearly defined contours, with often detected calcifications and septa. The walls of echinococcal cysts and septa are enhanced after the administration of contrast.

Classification of kidney cysts according to Bosniak

- assumes a conditional division of all renal cysts into 4 classes depending on the degree of their oncological alertness - from 1st (uncomplicated simple cysts) to 4th (definite malignant neoplasm).

The images show an example of a simple cyst of the lower pole of the right kidney, which does not contain a soft tissue component, septa, hemorrhages or calcifications in its structure. This cyst belongs to category 1 according to Bosniak.

Pelvicalyceal complex

- a structure consisting of the renal calyces and the renal pelvis.

Kidney contusion

- traumatic injury to the kidney, in which the leading sign on CT is edema, manifested in the form of an increase in the size of the kidney, blurred contours, and narrowing of the pyelocaliceal complex.

Corticomedullary phase

- one of the phases of contrast in computed tomography of the kidneys, obtained by scanning 20-30 seconds after the administration of contrast, performed for the purpose of visualizing the renal vessels, as well as well-vascularized kidney tumors.

CT urography

— display of the pyelocaliceal complex of the kidney and ureters obtained with CT scan of the kidneys after the injection of contrast into the vein.

Kidney lymphoma

- most often a secondary kidney disease that occurs with non-Hodgkin's lymphoma, as well as with post-transplant lymphoma. Renal lymphoma on CT may look like: a solitary node, deforming the contours of the kidney and infiltrating perirenal fat; multiple nodes of both kidneys up to 5 cm in size, which are clearly visible after contrast enhancement; diffuse changes in the kidney in the form of a decrease in the degree of enhancement of the renal parenchyma in the nephrographic phase and a decrease in renal excretion; retroperitoneal node - with fouling of the renal sinus and ureter.

Damage to the lymph nodes at the hilum of the kidney in lymphoma.

Kidney lipoma

- a tumor containing only adipose tissue (density -80...-120 Hounsfield units).

An example of a small lipoma of the left kidney is a peripherally located hypodense, rounded area with a fat density (in this example -100 Hounsfield units).

Mesenchymal kidney tumors

- a collective term that includes tumors such as lipomas, fibromas, leiomyomas, histiocytomas - rare tumors that do not have specific signs on CT scans of the kidneys.

Kidney metastases

- secondary kidney damage due to tumors of a different location. For example, bronchogenic cancer can metastasize to the kidneys. On CT, renal metastases may appear as multiple hypodense in the nephrographic phase of formation. The presence of metastases in other organs - adrenal glands, liver - is also characteristic.

Native CT scan of the kidneys

- computed tomography of the kidneys, performed without the introduction of a contrast agent. Used for the diagnosis of urolithiasis, obstructive lesions of the maxillary tract and ureters, and to identify high-density stones.

Chronic interstitial nephritis

- a disease of the renal interstitium caused by taking analgesics for a long time. A computed tomography scan of the kidneys reveals changes in the form of a decrease in the size of the kidneys and the formation of calcifications of the renal papillae.

Atrophic changes in both kidneys due to interstitial disease.

Nephroblastoma

— syn. Wilms tumor is a tumor of the renal parenchyma, most often found in childhood (up to 5 years). On CT, nephroblastoma is visualized as a hypodense formation, deforming the contour of the kidney, having heterogeneous density due to hemorrhages and necrotic foci, less often - fat and calcifications. Metastasizes to the lymph nodes at the hilum of the kidney, to the para-aortic lymph nodes.

Nephrographic phase

- one of the phases of contrast enhancement in CT scans of the kidneys, in which the renal cortex and medulla have the same density. This phase occurs 80-120 seconds after the administration of contrast, in which the probability of detecting tumors, especially small ones, is highest.

Nephrocalcinosis

- total calcification of the medulla and cortex of the kidneys, which on computed tomography become sharply hyperdense and extremely dense.

Nephroptosis

- low location of the kidney, low origin of the renal artery on the corresponding side, an atypically long and tortuous ureter.

Reformation in the coronal plane demonstrated moderate right-sided nephroptosis. Pay attention to the level at which the right and left kidneys are located - the right one is at least 2/3 of the height of the lumbar vertebra below.

Nephrectomy

- surgical removal of the kidney. A CT scan reveals scar tissue in the renal bed if the operation was performed long ago, and fresh blood and swelling in recent cases.

Case demonstrating right nephrectomy. The CT image shows a single left kidney, and a metal clip on the right vascular bundle of the kidney.

Inferior vena cava tumor thrombosis

– a condition that can occur when a kidney tumor (right) grows into the inferior vena cava. It indicates the advanced stage of the tumor process and is a marker of stage T4 according to the TNM classification.

Tumor of the upper pole of the right kidney grows into the inferior vena cava, in which multiple gas bubbles are also visualized. The prognosis in this case is extremely unfavorable.

Obstruction of the ureteropelvic junction

- a congenital anomaly of the kidneys, manifested by narrowing in the area of ​​​​the transition of the pelvis to the ureter, which does not lead to the development of hydronephrosis.

Oncocytoma

- benign tumor of the kidney from the epithelium of the renal tubules. On computed tomography of the kidneys, it looks like a single formation with expansive growth, equal in density to the hepatic parenchyma in native studies and intensifying after the introduction of contrast in the form of a “wheel with spokes” due to the presence of a central scar of a characteristic (star-shaped) shape.

Perl-Mann tumor

— syn. renal cystadenoma, multilocular cystic nephroma.

Kidney papilloma

- a common tumor characterized by damage to any part of the urinary tract - renal pelvis, ureter, bladder. It is a precancerous condition.

Anterior pararenal space

- an anatomical area containing fatty tissue, directly adjacent to the anterior fascia of Gerota on one side, and to the capsule of the spleen and pancreas on the other side.

Pararenal space posterior

- an anatomical area in which fatty tissue is located, limited by the posterior fascia of Gerota on one side, and the lumbar muscles on the other.

Perirenal space

- an area delimited by the anterior and posterior fascia of Gerota, containing perirenal fat (the fatty “capsule” of the kidney).

Persistent embryonic lobulation of the kidney

- a development variant in which defects in the contour of the renal parenchyma are detected towards the renal columns.

Pyelonephritis

- inflammation of the renal interstitium with involvement of the pelvis in the process, caused by an infectious agent. With pyelonephritis, CT can detect an enlarged kidney, blurred contours due to edema of the renal parenchyma and perirenal tissue, as well as local thickening of Gerota's fascia - if the inflammatory process spreads to them.

Changes in the kidney on CT scan with pyelonephritis.

Emphysematous pyelonephritis

- a severe variant of the inflammatory process in the kidney, caused by the development of gas-forming flora, which on computed tomography of the kidneys manifests itself as the presence of gas bubbles in the perinephric tissue, under the kidney capsule, in the pelvis, as well as signs of edema.

Pyelonephritis xanthogranulomatous

- a chronic inflammatory process in the renal cortex and in the medulla, which occurs secondary to obstruction of the urinary tract due to urolithiasis. Occurs mainly in women. With xanthogranulomatous pyelonephritis, stones in the renal pelvis are often detected, sometimes coral-shaped ones, as well as signs of hydronephrosis, with expansion of the calyces and the presence of detritus and xanthoma bodies in their cavities.

Pyonephrosis

- a condition that develops when the kidney is infected against the background of existing hydronephrosis. A CT scan of the retroperitoneum during pyonephrosis reveals a significant expansion of the renal collecting system with the presence of infected fluid with a density of 20...30 Hounsfield units.

Caseous pyonephrosis

- the final stage of development of kidney tuberculosis, in which caseous purulent melting occurs, followed by wrinkling and diffuse calcification.

Pyocalyx

- infection of one group of calyces with existing hydronephrosis or hydrocalyx - a local variant of pyonephrosis.

Squamous cell kidney cancer

- malignant kidney formation with a tendency to invasive growth. The tumor is localized in the renal pelvis and has the appearance of a node with a lobular structure. May cause hydronephrosis due to obstruction of the urinary tract. In the bladder with squamous cell kidney cancer, hyperdense blood clots can be seen.

Horseshoe kidney

- fusion of the kidneys in the region of the lower pole due to the presence of an isthmus consisting of connective or renal tissue. The kidney has the characteristic appearance of a horseshoe.

An example of visualization of a horseshoe kidney on contrast-enhanced computed tomography in the arterial and excretory phases. In the right image, arrows indicate the renal arteries (there are two of them, one on each side of the horseshoe kidney), in the image on the left and in the middle, arrows indicate separate ureters.

Renal vein thrombosis

- obstruction of the patency of the renal vein as a result of its occlusion by a thrombus. On CT, the renal vein is sharply dilated, full of blood (sometimes more than 2 cm), the degree of contrast enhancement of the vein is lower compared to the other side. In some cases, it is possible to directly visualize a thrombus in the lumen of the vein. If the thrombus intensifies in the arterial phase, a tumor of the renal vein can be suspected.

Kidney Page

- compression of the kidneys by large hematomas located subcapsularly, and the development of secondary renal hypertension.

Simple renal cyst

- hypodense formation with a density of 10...15 Hounsfield units in the kidney, not containing a solid component, calcifications, septa, blood. A common finding on CT scans of the kidneys. Simple cysts are not enhanced by contrast.

Pseudotumor of the kidney

- a volumetric process of the kidney, simulating tumor growth, but being a reflection of normal anatomical renal structures, for example, an enlarged column of Bertinius - an outgrowth of the renal cortex.

Renal rupture

- damage to the cortical and (or) medulla of the kidney, expressed to varying degrees depending on the applied traumatic force and the conditions of the injury.

Renal rupture, AAST classification

- 1 tbsp. - contusion or hematoma of the kidney; 2 tbsp. - renal cortex rupture less than 1 cm without urine extravasation; 3 tbsp. - a rupture of the renal cortex of more than 1 cm without damage to the collecting system and without extravasation of urine; 4 tbsp. - rupture of the renal parenchyma (cortical and medulla of the kidney, as well as the collecting system); 5 tbsp. - rupture of the parenchyma as in the case of stage 4, but with separation of the vascular bundle of the kidney and its devascularization.

Ureteral cancer

- looks on a CT scan of the ureters as a formation of soft tissue density, causing obstruction of the lumen and the development of hydroureter, and then hydronephrosis, or as thickening of the ureteral wall. In this condition, the distal part of the ureter is distended, filled with urine with a density of 12...20 Hounsfield units.

Renal cortical necrosis

- a condition in which death of the renal cortex occurs in a limited area or diffusely against the background of sepsis, septic shock. A CT scan of the kidneys with contrast in case of renal necrosis can reveal the absence of contrast in the renal cortex, and subsequently - after a week or more - calcification of the cortical layer begins and the progression of atrophic changes in the kidneys.

Soft tissue ring sign

— display of a thickened wall of the ureter when it is obstructed by a high-density calculus. On computed tomography, the ureter on axial sections appears as a ring structure with a hypodense wall (ring) and a hyperdense center (urinary stone).

An observation illustrating the symptom of a “soft tissue ring” during ureteral obstruction with a calcified stone – a high-density center and a low-density soft tissue “rim” along the periphery.

Stage T of renal cell carcinoma

(according to the TNM classification) - determined based on the size of the tumor node and its invasion of surrounding tissues. T1 - a node less than 7 cm in largest size, localized in the renal parenchyma; T2 - a node larger than 7 cm in largest size, localized in the kidney; T3 - invasion of perinephric tissue, as well as adjacent vessels, is observed; T4 - tumor invasion of the anterior or posterior fascia of Gerota is observed.

An example of renal cell carcinoma in different phases of contrast enhancement: native, arterial and acute. The tumor node corresponds to T1 stage according to TNM, since it is less than 7 cm in diameter and does not grow into surrounding tissues.

Stage N renal cell carcinoma

(according to TNM classification) - displays damage to the lymph nodes. N1 - there is a single enlarged lymph node less than 2 cm in largest size; N2 - there is a single lymph node more than 2 cm in largest size, or multiple lymph nodes less than 5 cm in size; N3 - there are lymph nodes larger than 5 cm.

Ureteral stricture

- a condition manifested by narrowing of the lumen of the ureter due to injury, inflammation, ionizing radiation (radiation therapy). Ureteral strictures are the cause of hydronephrosis.

Kidney tuberculosis

- one of the most common forms of extrapulmonary localization of tuberculosis infection. With computed tomography, renal tuberculosis usually does not give specific symptoms and manifests itself in the form of a productive form (with the presence of multiple tubercles in the cortical layer, hypodense in relation to the parenchyma), or an ulcerative-cavernous form (in the form of destructive changes in the kidneys with the development of multiple abscesses, the appearance calcifications, atrophic changes in the kidney parenchyma).

Perirenal fat severity

- a sign of urinary tract obstruction caused by urolithiasis.

Kidney duplication

- a developmental anomaly consisting in the presence of two separate fully formed kidneys on one side, supplied with blood by separate renal arteries, the outflow of venous blood from which is carried out through separate renal veins.

Duplication of the renal pelvis

- a development option in which there are two separate pelvises (and often two ureters) in one kidney.

Duplication of the ureter

- a development variant manifested by the presence of two separate ureters (in this case, duplication of the renal pelvis can also be detected). Duplication of the ureter can also be detected only in the upper sections - the so-called. ureter fissus.

Urolithiasis

- a term denoting the presence of urinary stones in the pyelocaliceal complex of the kidney and (or) in the ureter.

Urothelial cancer

- a malignant tumor of the renal pelvis, often also affecting the ureter and bladder.

Gerota's fascia anterior

— syn. anterior renal fascia is a connective tissue septum that separates the retroperitoneal tissue, in which the kidneys are located, from the fatty tissue of the abdominal cavity.

Gerota's fascia posterior

— syn. Zuckerkandl's fascia is a connective tissue septum delimiting the fatty capsule of the kidney at the back.

Fibrolipomatosis of the pelvis

- formation of the renal pelvis with a density corresponding to the density of fat and higher - depending on the ratio of connective tissue and fat components. Fibrolipomatosis is characterized by low-intensity sharp contrast enhancement.

Kidney cystadenoma

- a benign tumor consisting of a large number of cysts filled with myxomatous contents. CT scan of the kidneys is visualized as a large tumor (at least 3 cm, consisting of many cysts, sharply demarcated from the surrounding tissues. In approximately half of the cases with cystadenoma, calcifications are detected; hemorrhages and necrosis are much less common.

Excretory phase

- one of the phases of contrast enhancement (late) in CT scans of the kidneys, in which the pyelocaliceal complex, ureters and bladder are contrasted. Performed more than five minutes after the start of contrast administration.

Excretory phase delayed

- performed 15 or more minutes after the start of contrast injection into the vein, it is used to detect urineomas, and also allows you to evaluate the retention time of contrast in the kidney tubules.

Extravasation of urine

- a condition that occurs as a result of a violation of the integrity of the wall in any part of the urinary tract and the release of urine into the surrounding tissue.

Urography

– display of the organs of the urinary system obtained from their contrast X-ray or tomographic examination.

Urography excretory

– X-ray examination of the organs of the urinary system (CT or classical radiography), the purpose of which is to visualize the organs of the urinary system after the introduction of water-soluble contrast into a vein.

Kidney tumors account for 2-3% of all malignant neoplasms. Most often they occur between the ages of 40-60 years. Among all kidney tumors, 80-90% are renal cell carcinoma. In recent years, the likelihood of its detection has been increasing, which is associated both with the increase in the number of all malignant tumors and with early preclinical diagnosis. The recognition of malignant formations, first of all, is made possible by constantly improving and widely used ultrasound examinations of the kidneys.

The first report on the use of ultrasound in the diagnosis of kidney tumors was published in 1963 by J. Donald. Since then, the accuracy of ultrasound diagnosis of kidney tumors has increased from 85-90% to 96-97.3%. When using modern technologies operating in tissue and second harmonic modes, as well as color Doppler and dynamic echo-contrast angiography, the sensitivity of ultrasound (ultrasound) is 100% with a specificity of 92 and predictability of a positive test of 98%, and a negative test of 100%.

In the literature, there are often publications devoted to errors not only in ultrasound, but also in other methods of radiation diagnostics. There is a point of view that up to 7-9% of all volumetric processes in the kidneys cannot be differentiated from operations for cysts, tumors, abscesses, etc. . The picture of a kidney tumor using ultrasound and other radiation diagnostic methods can be simulated by many processes. Among them: various kidney anomalies; “complex” or mixed cysts; acute and chronic nonspecific inflammatory processes (carbuncle, abscess, chronic, including xanthogranulomatous pyelonephritis); specific inflammatory processes (tuberculosis, syphilis, fungal infections of the kidneys); changes in the kidneys with leukemia and lymphomas, including HIV infection; kidney infarctions; organized hematomas and other reasons.

In this message we will only talk about kidney anomalies, which in the literature are defined by the term pseudotumors. With them, clinical manifestations are almost always absent or determined by concomitant diseases, and establishing the correct diagnosis is possible only by radiological diagnostic methods (Fig. 1).

Rice. 1. Variants of pseudotumors that mimic a tumor.

A) Fetal lobulation, “humpbacked” kidney.

b) Hypertrophy of Bertin's column, enlarged “lip” above the renal hilum.

Materials and methods

For 1992-2001 177 patients with different structures of the renal parenchyma according to the type of renal pseudotumors were observed. All of them underwent repeated ultrasound scans of the kidneys, Doppler ultrasound (USDG) of renal vessels - 78, including using the second and tissue harmonic modes - 15, excretory urography (EU) - 54, X-ray computed tomography (X-ray computed tomography) - 36, renal scintigraphy or emission computed tomography (ECT) with 99 m Tc - 21.

Research results

Fetal lobulation of the kidney (see Fig. 1) with multiple protrusions along the lateral contour of the kidney was not considered in this report, since it did not require differential diagnosis with a kidney tumor. Among 177 patients with renal pseudotumors, 22 (12.4%) had a variant of the lobulated kidney - “humpbacked” kidney” (Fig. 2).

Rice. 2. Pseudotumor "humpback" left kidney.

A) Echograms.

b) A series of computed tomograms.

In 2 (1.2%) patients, an enlarged “lip” above the renal hilum was noted (Fig. 3a-c).

Rice. 3 (a-c). Pseudotumor is an enlarged “lip” of the kidneys on both sides.

A) Echogram.

b) Excretory urogram.

V) Contrast-enhanced CT.

The most common cause of pseudotumor was “hypertrophy” of Bertin’s columns or “bridges” of the renal parenchyma - in 153 (86.4%) patients (Fig. 3 d-f). “Bridges” of the parenchyma were noted not only with various duplications of the renal pyelocaliceal systems, but also with their various fusions and incomplete rotations of the kidneys.

Rice. 3 (d-f). Pseudotumor Bertin's hypertrophy (incomplete "bridge" of parenchyma) in the middle section of the right kidney.

G) Echogram.

d) Excretory urogram.

e) Contrast-enhanced CT.

37 (21%) patients required differential diagnosis of pseudotumors and renal tumors. For this purpose, first of all, repeated “targeted” ultrasound scans were carried out using various additional ultrasound techniques in a urological clinic, as well as other methods of radiation diagnostics mentioned above. In only one patient with a pseudotumor of the kidney, an exploratory lumbotomy with intraoperative ultrasound-guided biopsy was performed to exclude the diagnosis of a tumor. In the remaining 36 patients, the diagnosis of renal pseudotumors was confirmed using radiation studies and ultrasound monitoring.

Difficulties and errors in radiological diagnostics for renal pseudotumors usually arose in the first pre-hospital stages of diagnosis. In 34 (92%) patients, they were associated with both objective difficulties in interpreting unusual echographic data, and their incorrect interpretation due to insufficient qualifications of specialists and the relatively low level of diagnostic equipment. In 3 (8%) patients, there was an erroneous interpretation of X-ray computed tomography data, when there was a discrepancy between them and the data of repeated ultrasound scans and X-ray computed tomography in the urology clinic.

Kidney tumors that were combined with a pseudotumor in one kidney were verified in 2 patients after nephrectomy, and pseudotumors were verified in one patient during ultrasound-guided biopsy during exploratory lumbotomy; for the rest - with ultrasound monitoring for periods from 1 to 10 years.

Discussion

One of the most common causes simulating a kidney tumor on ultrasound, the so-called pseudotumor, is most often defined in the literature by the term hypertrophy of Bertin's column.

As is known, along the periphery of an ultrasound section of the kidney, the cortex forms invaginations in the form of columns (columnae Bertin) between the pyramids. Often Bertin's column extends quite deeply beyond the internal contour of the parenchyma into the central part of the kidney - into the renal sinus, dividing the kidney more or less completely into two parts. The resulting peculiar parenchymal “bridge” is the unresolved parenchyma of the pole of one of the kidney lobules, which merge into the kidney of an adult during the process of ontogenesis. The anatomical substrate of the “bridges” is the so-called connective tissue defects of the parenchyma or prolapse of the latter into the renal sinus. It consists of the cortex, Bertin's columns, and renal pyramids.

All elements of the “bridge” are normal parenchymal tissue without signs of hypertrophy or dysplasia. They represent a duplication of the normal renal cortex or an additional layer of it located lateral to the calyces. The latter is a variant of the anatomical structure of the parenchyma, in particular, the corticomedullary relationship between the parenchyma and the renal sinus. They can be most clearly seen on ultrasound and computed tomographic sections of the kidney.

The absence of hypertrophy or dysplasia of the parenchyma with the so-called hypertrophy of Bertin’s columns or “bridges” of the parenchyma was confirmed by histological studies of biopsy material in one patient with “bridges” of the parenchyma, which were taken before explorative lumbotomy for a kidney tumor, as well as in two patients during a morphological study of the kidneys, removed due to a combination of a tumor and a pseudotumor (“bridge” of parenchyma) in one kidney.

In this regard, in our opinion, the term hypertrophy of Bertin's columns, which is most often found in the literature, does not reflect the morphological essence of the substrate. Therefore, we, like a number of authors, believe that the term “bridge” of parenchyma is more correct. We used it for the first time in the domestic literature on ultrasound diagnostics in 1991. It should be noted that the term “bridge” of parenchyma had other names in the literature (table).

Table. Terms used to describe the “bridges” of the renal parenchyma (according to Yeh HC, Halton KP, Shapiro RS et al., 1992).

Origin or nature of the fabric	Terms	Authors
Hypertrophied or unusually wide tissue	Hypertrophied Bertin's column	Lafortune M et al., 1986 Wolfman NT et al., 1991 Leekman RN et al., 1983
	Focal cortical hyperplasia	Popky G.L. et al., 1969
	Wide arcade	Hodson CJ et al., 1982
Incorrectly positioned or displaced tissue	Lobar dysmorphism	Carghi A et al., 1971 Dacie JE, 1976
	Incorrect position of the renal lobe	Carghi A et al., 1971
	Cortical folds	King MC et al., 1968
	"Kidney" within a kidney	Hodson CJ et al., 1982
	Cortical intussusception and prolapse of Bertin's columns	Lopez FA, 1972
Mass or pseudo mass	Renal pseudotumor	Felson B et al., 1969 Lopez FA, 1972
	Glomerular zone of pseudotumor	Hartman GW et al., 1969
	Renal-cortical nodule	Wolfman NT et al., 1991
	Primary cortical nodule	Thornbury JR et al., 1980
	Intermedial cortical mass	Netter F et al., 1979
Embryonic anomaly	Aberrant lobule of renal tissue	Meaney TF, 1969
	Benign cortical "caesura"	Flynn VJ et al., 1972
	Cortical islet of the kidney	Flynn VJ et al., 1972
Developed (perfect) anomaly	Failed attempt at duplication of renal parenchyma	Dacie JE, 1976
Supernumerary share	Accessory renal lobe	Palma L.D. et al., 1990

Many years of experience in excretory urography have shown that the collecting system has an extremely large number of structural options. They are practically individual not only for each person, but also for the left and right kidneys of the same subject. With the development and increasingly widespread use of ultrasound and X-ray CT, which makes it possible to trace both the internal and external contours of the renal parenchyma, in our opinion, a similar situation is emerging with regard to the variants of the anatomical structure of the renal parenchyma. A comparison of echo and computed tomographic data with urographic data for various types of renal pseudotumors showed that there is a relationship between the anatomical structure of the parenchyma and the renal collecting systems. It is expressed in the congruence of the medial contour of the parenchyma in an echo or computed tomographic image with the lateral contour of the pyelocaliceal systems, conventionally drawn on excretory urograms or on contrast-enhanced computed tomograms. This symptom can be traced with the usual structure of the parenchyma and pyelocaliceal systems, as well as with the “bridge” of the kidney parenchyma, which is a variant of the anatomical structure. With a kidney tumor, which is an acquired pathological process, the congruence of the contours of the parenchyma and the renal collecting systems is disrupted (Fig. 4).

Rice. 4. A symptom of congruence of the contours of the parenchyma and the pyelocaliceal system of the kidney with an incomplete “bridge” of the parenchyma (explanation in the text).

Conclusions

Thus, the typical echographic images of a “bridge” of the renal parenchyma, a “humpbacked” kidney and an enlarged “lip” above the renal hilum without signs of dilation of the pyelocaliceal systems, first identified by ultrasound, do not require further examination.

If differential diagnosis of pseudotumors and renal tumors is necessary, which was required in 37 (21%) patients, we propose the following algorithm for their diagnosis (Fig. 5).

Rice. 5. Radiation diagnostic algorithm for renal pseudotumor.

1. Repeated ultrasound by qualified specialists of a higher class using ultrasound, mapping techniques, tissue and second harmonics.
2. X-ray computed tomography with contrast enhancement or excretory urography with comparison of uro- and echographic data and data from a repeated “targeted” ultrasound.
3. The methods of choice are renal scintigraphy or emission computed tomography with 99 m Tc (false-negative results are possible for small tumors).
4. If there is still suspicion of a malignant tumor, a biopsy under ultrasound guidance (only a positive result has diagnostic value).
5. If the biopsy result is negative or the patient refuses a biopsy and surgical revision of the kidney, ultrasound monitoring is performed at least once every 3 months in the first year of observation, and then 1-2 times a year.

Literature

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2. Hutschenreiter G., Weitzel D. Sonographic: einewertwolle erganzung der urologichen Diagnostic // Aktuel. Urol. 1979. Vol. Bd 10 N 2. P. 45-49.
3. Nadareishvili A.K. Diagnostic capabilities of ultrasound in patients with kidney tumors // 1st Congress of the Association of Ultrasound Diagnostics in Medicine: Abstracts. Moscow. October 22-25, 1991. P.121.
4. Buylov V.M. Complex application and algorithms of ultrasound scanning and x-ray diagnostics for diseases of the kidneys and ureters: Dis. ... doc. honey. Sci. M., 1995. P. 55.
5. Modern ultrasound diagnostics of volumetric formations of the kidneys / A.V. Zubarev, I.Yu. Nasnikova, V.P. Kozlov et al. // 3rd Congress of the Association of Ultrasound Diagnostics Specialists in Medicine: Abstracts of reports. Moscow. October 25-28, 1999 P. 117.
6. US, CT, X-ray diagnosis of Renal Masses / R.K. Zeman, J.J. Croman, A.T. Rosenfield et al. // Radiographics. 1986. Vol.6. P. 351-372.
7. Thomsen H.S., Pollack H.M. The Genitourinary System // Global TextBook of Radiology. (Ed.) Petterson H. 1995. P. 1144-1145.
8. Lopatkin N.A., Lyulko A.V. Anomalies of the genitourinary system. Kyiv: Zdorovya, 1987. P. 41-45.
9. Mindel H.J. Pitfalls in Sonography of Renal Masses // Urol. Radiol. 1989. 11. 87. N 4. R. 217-218.
10. Burykh M.P., Akimov A.B., Stepanov E.P. Echography of the kidney and its pyelocaliceal complex in comparison with data from anatomical and x-ray studies // Arch. Anat. Gistol. Embryol. 1989. T.97. N9. P.82-87.
11. Junctional Parenchyma: Revised Definition of Hypertrophic Column of Bertin / H-Ch. Yeh, P.H. Kathleen, R.S. Shapiro et al. // Radiology. 1992. N 185. R. 725-732.
12. Bobrik I.I., Dugan I.N. Anatomy of the human kidneys during ultrasound examination // Doctor. case. 1991. N 5. P. 73-76.
13. Khitrova A.N., Mitkov V.V. Renal ultrasound: Clinical guide to ultrasound diagnostics. M.: Vidar, 1996. T. 1. S. 201-204, 209, 212.
14. Builov V. Junctional parenchyma or hypertrophic column of Bertini: the congruence of their contours and calyceal-pelvic system // Abstracts of ECR ​​"99, March 7-12. 1999. Vienna Austria.-Europ. Radiol. Supp. 1. Vol. 9. 1999. S.447.
15. Builov V.M., Turzin V.V. Echotomography and excretory urography in the diagnosis of “bridges” of the renal parenchyma // Vestn. radiol.radiol. 1992. N 5-6. pp. 44-51.
16. Builov V.M., Turzin V.V. Diagnostic value of atypical “bridges” of parenchyma during sonography of the kidneys // 1st Congress of the Association of Ultrasound Diagnostics in Medicine: Abstracts of reports. Moscow. October 22-25, 1991. P. 121.
17. Buylov V.M. Questions of terminology and a symptom of congruence of the contours of “hypertrophied” columns of Bertini or “bridges” of the parenchyma and pyelocaliceal systems of the kidneys // Vestn. rentgenol. and radiol. 2000. N 2. P. 32-35.
18. Buylov V.M. Algorithm for radiodiagnosis of renal pseudotumors // Abstracts of reports. 8th All-Russian Congress of Radiologists and Radiologists. Chelyabinsk-Moscow. 2001. pp. 124-125.

Modern ultrasound diagnosis of kidney diseases is impossible without a clear understanding of the normal echoanatomy of the kidney, based on a comparison of the echographic picture and the histomorphological substrate.

Issues of normal echoanatomy of the kidney are quite fully covered in foreign textbooks, monographs, articles and are not sufficiently covered in the domestic literature.

The kidneys are located retroperitoneally. The right kidney is at the level of Th-12-L-4, the left kidney is located higher – at the level of Th-11-L3 vertebra. However, determining the position of the kidney relative to the vertebrae is quite inconvenient, therefore, in echographic practice, the hypoechoic acoustic “shadow” from the twelfth rib, the dome of the diaphragm (or the diaphragmatic contour of the liver), the hilum of the spleen, and the contralateral kidney are used as a guide to determine the position of the kidney. Normally, the acoustic “shadow” from the twelfth rib crosses (during longitudinal scanning from the back parallel to the long axis of the kidney) the right kidney at the level of the boundaries of the upper and middle third, the left kidney at the level of the renal hilum. The upper pole of the right kidney is located at the level or slightly below the upper phrenic contour of the right lobe of the liver. The upper pole of the left kidney is located at the level of the hilum of the spleen. The distances from the upper pole of the right kidney to the contour of the diaphragm and from the upper pole of the left kidney to the hilum of the spleen depend on the degree of development of the perinephric tissue of the subject.

Kidney sizes, according to N.S. Ignashin, are 10-12 cm and 3.5 - 4.5 cm in a longitudinal section, 5-6 cm and 3.5 - 4.5 cm in a transverse section. The total thickness of the parenchyma is 1.2 - 2.0 cm in the middle segment, 2.0 – 2.5 cm in the region of the poles of the kidney. The normal kidney volume is 300 cm3. According to V.N. Demidov, kidney length 7.5 – 12 cm, width 4.5 – 6.5 cm, thickness 3.5 – 5 cm. According to M.P. Burykh and the specialists who carried out anatomical-echographic correlations, the length of the kidney is 10.41 + 1.3 cm, the width of the kidney is 5.45 ± 1.3 cm, and the thickness is 3.63 ± 0.5 cm.

The cut shape of a normal kidney in all projections is bean-shaped or oval. The contour of the kidney is usually smooth, and if there is preserved fetal lobulation of the kidney, it is wavy (this is a variant of the normal structure of the kidney). Quite often, a local bulging of the contour is normally detected in the area of ​​the lateral edge of the kidney (in this case, the so-called “humpbacked” kidney is defined) or in the area of ​​​​the edge of the renal sinus, which simulates a kidney tumor. These conditions are described as pseudotumors and are also variants of the normal kidney structure. One of the distinctive features of pseudotumor “bulges” of the parenchyma with preserved fetal lobulation of the kidney, in contrast to the tumor, is the preservation of parallelism of the outer and internal contours of the parenchyma, the preservation of the normal echostructure of the parenchyma.

In Fig. Figure 18 shows an echogram of a normal adult kidney.

The sonographic characteristics of the renal capsule and parenchyma of the normal kidney are generally accepted. Along the periphery of the ultrasound section of the kidney, a fibrous capsule is visible in the form of a hyperechoic, smooth, continuous structure 2–3 mm thick, then the parenchyma layer is determined. The renal hilum is located echographically in the form of a “break” in the medial contour of the renal parenchyma, and when scanning from the anterior abdominal wall at the top of the scan, an anteriorly located anechoic tubular structure is visualized - the renal vein, located behind the hypoechoic renal artery. The parenchyma is heterogeneous and consists of two layers: the cortex and the medullary (or the substance of the kidney pyramids). The morphological substrate of the renal cortex (kidney cortex) is predominantly the glomerular apparatus, convoluted tubules, interstitial tissue containing blood and lymphatic vessels, and nerves. The medullary substance contains loops of Henle, collecting ducts, ducts of Bellini, and interstitial tissue. The renal cortex is located along the periphery of the ultrasound section of the kidney with a thickness of 5–7 mm, and also forms invaginations in the form of columns (columnae Bertini) between the pyramids. In Fig. 19, 20 present a schematic representation of the parenchyma layers and a technique for measuring the thickness of the parenchyma elements. Often, Bertin's column extends quite far beyond the internal contour of the parenchyma into the central part of the kidney - into the renal sinus, dividing the kidney more or less completely into two parts. The resulting peculiar parenchymal “bridge,” the so-called hypertrophied column of Bertin, is the unresolved parenchyma of the pole of one of the kidney lobes, which merge during ontogenesis to form an adult kidney. This bridge consists of the cortex, columns of Bertin, and pyramids of the kidney. All elements of the bridge are normal parenchymal tissue without signs of hypertrophy or dysplasia.

Therefore, the name “hypertrophied Bertin column” existing in the literature does not reflect the morphological essence of the substrate, and, probably, the definition of Zh.K. Ena et al., who called this formation a parenchymal bridge. The echogenicity of the renal cortex is usually slightly lower or comparable to the echogenicity of the normal liver parenchyma. The kidney pyramids are defined as triangular-shaped structures with reduced echogenicity compared to the cortex. In this case, the top of the pyramid (pyramidal papilla) faces the renal sinus - the central part of the kidney slice, and the base of the pyramid is adjacent to the parenchyma cortex, located along the periphery of the slice (see Fig. 19). The renal pyramids have a thickness of 8–12 mm (the thickness of the pyramids is defined as the height of the triangular structure, the apex of which faces the renal sinus), although the normal size of the pyramids largely depends on the level of diuresis. Normally, the echographic differentiation of the cortex and pyramids is pronounced: the echogenicity of the cortical substance is significantly higher than the echogenicity of the pyramids of the kidney. Often this difference in echogenicity is the cause of a false-positive diagnosis of hydrocalycosis, when very dark, low-echogenicity pyramids are mistaken by novice ultrasound doctors for dilated cups. Modern histomorphological studies of the kidney parenchyma and their comparison with the echographic picture suggest that the pronounced echographic corticomedullary differentiation is due to a significant difference in the number of fat vacuoles in the epithelium of the tubular structures of the cortex and pyramids. However, it is impossible to explain the different echogenicity of the cortex and pyramids only by the different content of fat vacuoles in the epithelium of tubular structures, since it is known that the echogenicity of the pyramids of the kidney at a high level of diuresis is significantly lower than the echogenicity of the pyramids of the same kidney under normal conditions, and the number of fat vacuoles depends on diuresis level does not change. It is also impossible to explain the low echogenicity of the pyramids by the presence of fluid in the tubular structures, since the resolution of the ultrasound device under any conditions does not allow differentiating the lumen of the tubule and the fluid in it. It can be assumed that the low echogenicity of the medullary substance is associated with:

1) with a high content of glycosaminoglycans in the interstitial tissue, where most of the functional processes providing ion exchange, reabsorption of water and electrolytes, and urine transport occur; glycosaminoglycans are able to “bind” liquid, according to the authors of the hypothesis, “swelling and swelling very quickly”;

2) the presence of smooth muscle fibers in the interstitial tissue surrounding the excretory ducts of the renal papilla.

In children, the echogenicity of the cortical substance is significantly higher than in adults, which is explained by a more compact arrangement of the glomeruli and less interstitial tissue. Pyramids occupy a larger area than those of adults. Morphometric studies have shown that in newborns the cortex and pyramids occupy about 90% of the kidney volume; in adults, the percentage decreases to 82%.

In the center of the echographic section of the kidney, a hyperechoic complex of oval or round shape (depending on the scanning plane) is determined, the renal sinus, the size and echogenicity of which varies largely depending on the age of the subject and his dietary habits.

If the echographic characteristics and interpretation of the image of normal parenchyma are generally accepted in medical practice and in scientific research, then the interpretation of the central echo complex varies significantly among different authors. In practical work, as well as in scientific articles of some authors, there is a semantic identification of the central echo complex and the renal collecting system. However, modern histomorphological and echographic correlations of a normal kidney have convincingly proven that the central echo complex is a summary reflection not of the collecting system, but of the entire set of elements of the renal sinus. By comparing anatomical and echographic data, it was established that it is the renal sinus, and not the pyelocaliceal system, as previously thought, that is the morphological substrate of the central echo complex.

Very little has been written about the renal sinus as an anatomical entity, although there is extensive medical research evidence describing various renal sinus pathologies. When an image is taken, many conditions give a similar picture. Misdiagnosis may occur when a diagnosis is attempted without considering various possibilities.

The renal sinus is a specific anatomical structure that surrounds and includes the collecting system of the kidneys. It borders on the lateral side with the renal pyramids and cortical columns. The medial renal sinus communicates with the panephric space through the renal hilum. The elements of the renal sinus are lymphatic, nervous, renovascular structures surrounded by fatty and fibrous tissue. A decrease in the percentage of parenchyma in the kidney volume in an adult compared to a newborn occurs precisely due to an increase in the volume of the renal sinus, which occurs as a result of the “age-related” growth of renal sinus tissue. The adipose tissue of the renal sinus is practically absent in the newborn, which is manifested echographically by the absence of reflected echo signals from the renal sinus or in a minimally expressed central echo complex in the form of a delicate, branched, weakly echogenic structure. In contrast to the adult kidney, the medullary layer is more pronounced, the central echo complex is represented by a branched structure that is smaller in area and echogenic. By the age of 10, the renal sinus is almost completely formed. Similar data were obtained from MR studies of the kidneys of healthy children (an intense signal on T 1-weighted images, corresponding to sinus tissue, appears in the age group of children over 10 years old. Normally, an age-related increase in the amount of renal sinus tissue is observed. In some cases, pathological proliferation of fiber (in 0.66 - 10% of cases) - sinus fibrolipomatosis. The most common sinus lipomatosis occurs after fifty years. It was found that the ratio of the anteroposterior size of the kidney to the anteroposterior size of the renal sinus in both kidneys in both males and females. inverse correlation with age. No significant correlation with gender has been identified. In addition to age, the causes of lipomatosis can be: obesity, steroid therapy, Cushing's syndrome. Replacement fibrolipomatosis occurs more often as a result of severe renal atrophy against the background of urolithiasis. in 3/4 of patients. If echography reveals an increase in the central echo complex against the background of coral nephrolithiasis, then, as a rule, this is a consequence of replacing fibrolipomatosis against the background of urolithiasis and chronic pyelonephritis. On nephrotomograms, renal sinus lipomatosis cannot be distinguished from renal sinus cysts - there is a classic picture of elongated and curved calyx necks. Some studies provide observations of echo-negative formations in the projection of the renal sinus, allegedly associated with the process of renal lipomatosis. According to I.S. Amis, who analyzed the reasons for the discrepancies between echography and nephrotomography data, these errors are associated with incorrect interpretation of X-ray negative zones in the projection of the renal sinus during nephrotomography. This assumption was confirmed in similar cases with computed tomography and puncture. Renal echography helps distinguish renal sinus lipomatosis from cysts. With sinus lipomatosis, there is an increase and increased echogenicity of the renal sinus.

So, the echogenicity of the central complex is determined, first of all, by the presence and amount of fatty tissue in the renal sinus. However, in addition to high-intensity reflections, the central echo complex contains small zones of reduced echogenicity and anechoic zones. For quite a long time it was believed that these zones are reflections of the elements of the collecting system. Data on the normal echographic dimensions of the pyelocaliceal system in adult subjects are extremely contradictory and sparse. Thus, in 1982, A. Deina reported on the “syndrome of echographic invisibility of the collecting system.” I.S. Amis calls dilatation of the collecting system any “splitting” of the collecting system by an echo-negative strip. K.K. Hayden, L.I. Svishuk assume that there is normally only a thin layer of fluid in the pyelocalyceal system. Moreover, the presence of expansion of the pelvis and calyx structures and their fusion in the form of a “tree” is, according to these authors, a sign of hydronephrosis. T.S. Hihashi, comparing data from echography, Dopplerography and excretory urography, came to the conclusion that the classification of hydronephrosis by P.Sh. Illenboden, who describes sonographically detected hydronephrosis by degree as a splitting of the central echo complex in the form of: a) a branchy tree structure, b) a lily structure, c) a clover structure, d) a rosebud-shaped structure, leads to a false-positive diagnosis of hydronephrosis. According to these authors, splitting of the central echo complex in the form of a tree corresponds to normal vascular structures, an echo-negative structure in the form of a lily corresponds to a normal pelvis or, possibly, an obstructive process, a structure in the form of a rosebud corresponds to the initial form of hydronephrosis, and a clover-shaped structure corresponds to severe hydronephrosis. At the same time, false-positive diagnosis of hydronephrosis occurred in 11%, false-negative – in 22% of cases. Quantitative estimates of the size of the normal pyelocalyceal system are not provided in the work of these authors. Although I. Hash tried to use the size of the pelvis as an index determining the degree of hydronephrosis, data defining the anteroposterior size of the pelvis as a differential diagnostic criterion for normal and pathological conditions was not given. F.S. Will considers the anteroposterior size of the pelvis to be 30 mm as the norm, which from our point of view is completely unacceptable. V.N. Demidov, Yu.A. Pytel, A.V. Amosov determines the normal anteroposterior size of the pelvis to be 1 – 2.5 cm. G.M. Imnaishvili believes that visualization of the calyces in the form of anechoic, rounded formations up to 5 mm in diameter is normally acceptable. The pelvis can be visualized as two hyperechoic linear structures extending towards the renal hilum.

The data from T.Ch. is quite interesting. Tzei et al. The study of the authors' data was undertaken with the aim of establishing the echographic dimensions of the normal renal pelvis in children and determining the correlation between its size and the presence of a particular renal pathology, as well as the dependence of the size of the pelvis on age. It was found that the upper limit of normal anteroposterior size in children is 10 mm, and only 1.7% of normal renal pelvis exceeded the size of 10 mm. Correlation analysis did not reveal statistically significant differences in the size of the renal pelvis in different age groups, although the average size values ​​in the normal group and in the pathology group were statistically different (p Potential causes of false-positive diagnosis of hydronephrosis, according to T.C. Tzei and other authors, are: overdistension of the bladder, increased urine flow (under the influence of diuretics, contrast agents, diabetic polyuria, overhydration), atony of the pelvis during acute inflammation, cystic changes in the kidney, simulating hydronephrosis. The reasons for a false negative diagnosis are: dehydration, acute obstruction without dilatation, distal obstruction. parts of the urinary tract, damage to the collecting system, incorrect interpretation of the normal image. To determine the capabilities of echography, pharmacoechography with a diuretic in the visualization of the collecting system, as well as to determine the echographic dimensions of the normal pelvis and calyces, we conducted studies in groups of healthy individuals under various drinking regimes and drinking conditions. degrees of bladder filling. When comparing the echographic picture of the renal sinus in B-mode and in color Doppler mapping mode, it was found that under conditions of water deprivation (when examined on an empty stomach) and with an empty bladder, all echo-negative zones in the renal sinus corresponded to zones of detectable blood flow. Elements of the pyelocaliceal system in the form of an- or hypoechoic structures were not identified. Moreover, in the subgroup of people under 30 years of age, the largest echo-negative structures corresponded to the venous vessels of the renal sinus and had an average diameter of 5.6 + 1 mm, in the middle age subgroup (up to 50 years old) - 4.9 ± 0.4 mm, in the older age group In a subgroup of individuals, venous structures were not so clearly visualized, and their average diameter was 3.8 ± 0.1 mm. Branches of the renal artery were typically identified as much smaller hypoechoic zones within the renal sinus. Almost all echo-negative zones corresponded to zones of detectable blood flow.

In a group of healthy individuals with a normal drinking regimen (1.5 liters of fluid per day) and average bladder filling (up to 250 ml), cup structures with a diameter of no more than 5 mm were visualized in 8% of the subjects.

In the third group of healthy individuals, a pharmacoechographic test with furosemide was used as a method of visualizing the pyelocaliceal system (PSS); At the same time, the possibilities of pharmacoechography in obtaining a clear echographic picture of the CLS were studied. The term “pharmacoechography” was introduced by A.V. Amosov and G.M. Imnaishvili in 1988. Pharmacoechography, as defined by these authors, is a study of urodynamics using diuretic medications under ultrasound guidance. Before the test, the authors determine the size of the pyelocaliceal system and assess the condition of the parenchyma. The patient is then given 20 mg of furosemide or bufenox at a dose of 2 ml of a 0.025% solution intravenously, followed by an ultrasound examination for 30 minutes or more. The effect of the drugs begins after 2–3 minutes and lasts for a relatively short time. The authors believe that with undisturbed passage of urine, the clarity of the image and the size of the cups and pelvis do not change after the administration of a diuretic. If the passage of urine is disturbed, if there are disturbances in urodynamics, ultrasound begins to reveal retention changes in the pyelocaliceal system.

In more recent works, pharmacoechography is used as a method of diagnosis and differential diagnosis of stenoses of the ureteropelvic segment to determine the degree of damage and the degree of reversibility of changes in obstructive nephropathies, for the purpose of differential diagnosis of true obstruction of the urinary tract in the fetus, diagnosis of renal sinus cysts. Magnitol is also used as a diuretic.

Our studies suggest the use of pharmacoechography as a way to visualize the pyelocaliceal system of the normal kidney. In this case, furosemide is administered intravenously or intramuscularly at the rate of 0.5 mg per kilogram of the patient’s weight against the background of high hydration (the subjects are asked to take 0.8 - 1.0 l of fluid an hour before the study). When the drug is administered intravenously, the effect occurs “at the tip of the needle.” The pyelocaliceal system begins to be visualized as a hypoechoic tree-like structure, splitting the central hyperechoic echo complex. In this case, the role of a kind of contrast, allowing visualization of the CLS against the background of the fatty tissue of the sinus, is played by the fluid, which more completely fills the cavities of the collecting system. Pay attention to how the echographic picture of the renal hilum has changed after the administration of furosemide - three anechoic structures are already visualized in the renal hilum: the renal vein, the artery and the posterior pelvis. With the intramuscular route of administration, the average time to start imaging increases and is 10.2 ± 5.3 minutes.

Summarizing all of the above about the echoanatomy of a normal kidney, we emphasize the most important points:

– a normal kidney does not necessarily have an even, but always clear (due to the presence of a capsule) contour;

– assessment of the position of the kidney is carried out in relation to nearby organs, as well as in relation to bone landmarks (mainly the 12th rib);

– when assessing the echostructure and echogenicity of the kidney, the presence or absence of corticomedullary differentiation, differentiation of the parenchyma and the renal sinus is determined, the echogenicity and echostructure of each element of the parenchyma and renal sinus are assessed;

– the central echo complex of the kidney section is a total reflection of the elements of the renal sinus, while the hyperechoic component of the complex is caused primarily by the fatty tissue of the renal sinus; hypo- and anechoic formations when examined on an empty stomach are due to the presence of vascular elements;

Kidney structure

The kidneys are located retroperitoneally in the lumbar region at the level of the last two thoracic and first two lumbar vertebrae. The right kidney is usually 1-2 cm lower than the left.

The kidney parenchyma consists of a cortex and pyramids. The renal columns (Bertini's columns) between the pyramids consist of the cortex. The pyramid and the cortical substance covering it form the renal lobule. At the top of the pyramid, the openings of the papillary tubules open.

The renal sinus contains the pyelocaliceal complex (PCC), vessels, nerves, connective tissue and fat. The small cup sits on the top of the pyramid like a breast pump on the nipple. Urine actively flows into the small and large calyces → renal pelvis → ureter → bladder → urethra.

Click on pictures to enlarge.

Kidney ultrasound

A 2.5-7.5 MHz convex sensor is used. If a pathology is suspected, the study is carried out with a full bladder when the urge to urinate appears. After urination, the kidneys are examined again.

We are interested in the location, size, echogenicity, echostructure of the kidneys, as well as the patency of the urinary tract. For more information, see how to assess kidney size in children and adults.

Bladder and distal ureter on ultrasound

With the patient lying on his back, we remove the bladder in the suprapubic region. Assess bladder filling and distal ureters. Normally, the distal ureter is not visible. A ureter more than 7 mm in diameter is a megaureter.

Drawing. Ultrasound shows an enlarged distal ureter (1, 2, 3). About ureterocele (3) see in more detail.

Echogenicity of the kidneys

With the patient in the supine position, along the midclavicular and anterior axillary line, we bring out the right kidney adjacent to the liver, and the left kidney near the spleen. Assess the echogenicity of the kidneys. The renal cortex is normally iso- or hypoechoic in relation to the liver and hypoechoic in relation to the spleen.

Drawing. The echogenicity of organs is compared on one section. Ultrasound shows a normal kidney adjacent to the liver (1) and spleen (2). In children under 6 months of age, the renal parenchyma may normally be hyperechoic compared to the liver (3).

Kidney shape on ultrasound

To view the upper pole of the kidney, ask the patient to take a deep breath. The shape of the kidney is bean-shaped - convex on the lateral side and concave on the medial side. An embryonic-lobulated kidney, as well as a humpbacked left kidney, are considered a variant of the norm.

Drawing. On ultrasound (1) and CT (2, 3) the contour of the kidneys is wavy. In the embryo, the kidney develops from separate lobules that fuse as they grow. The lobulated structure of the kidneys is clearly visible in the fetus and newborns; in isolated cases, it persists in adults.

Drawing. You can find a humpbacked left kidney - a convex, uneven outer contour due to hypertrophy of the parenchyma in the middle third of the kidney. It is believed that the “hump” is formed in the fetus under pressure from the lower edge of the spleen.

Drawing. Scanning from the anterior abdominal wall allows us not to miss the isthmus between the kidneys. The isthmus in front of the spine is evidence of fusion of the kidneys - a horseshoe kidney. See variations of the anatomy of horseshoe kidneys.

Video. Horseshoe-shaped kidney on ultrasound

Echostructure of the kidneys

In a normal kidney, the pyramids are hypoechoic, the cortex and columns of Bertini are isoechoic to each other. In the sinus there is normally an invisible PCL, hyperechoic connective and adipose tissue, hypoechoic vessels and the apices of the pyramids.

When pyramids, cortex, and renal columns are distinguished, the echostructure of the renal parenchyma is not changed. If they are not visible, then the echostructure is changed due to the lack of clear cortical-cerebral differentiation.

Drawing. Ultrasound shows a kidney with an unchanged echostructure: hypoechoic in relation to the liver, cortical layer and columns of Bertini, almost anechoic pyramids, hyperechoic sinus.

Drawing. In 37% of healthy newborns, the symptom of “white pyramids” is detected by ultrasound on the first day of life. Precipitation of Tamm-Horsfall protein and uric acid causes reversible tubular obstruction. By 6 weeks of life it goes away without treatment.

Drawing. Ultrasound of a healthy kidney: along the base of the pyramids (corticomedullary junction) linear hyperechoic structures with a hypoechoic track in the center are identified. These are arcuate arteries, which are mistakenly regarded as nephrocalcinosis or stones.

Video. Arc-shaped arteries of the kidney on ultrasound

Drawing. On ultrasound, the lower pole of the kidney is separated by a hyperechoic fibrous bridge; pelvis of the lower segment 7 mm. This is a variant of the normal structure of the kidney. The kidney may be deformed, so its size and length are slightly smaller than the opposite one. A slight expansion of the pelvis under the bridge persists for life.

Video. Ultrasound shows a fibrous bridge in the kidney (structural variant)

Sometimes Bertini's column cuts into the central part of the kidney, dividing it completely or incompletely into two parts. Such a parenchymal bridge is the parenchyma of the pole of one of the embryonic lobules, which fuse to form a kidney; consists of bark, pyramids, columns of Bertini - all elements without signs of hypertrophy or dysplasia. The term hypertrophy of Bertini's column does not reflect the morphology of the structure; it is more accurate to consider this formation as a parenchymal bridge.

Drawing. On ultrasound, a round formation divides the renal sinus into two segments with a common pelvis; interlobar arteries go around the formation; the echogenicity and intensity of the vascular pattern inside is close to the cortical zone. Conclusion: Hypertrophy of Bertini's column or incomplete parenchymal bridge. This is a variant of the normal structure of the kidney. The term “incomplete doubling of the maxillofacial area” is incorrect, because an incomplete parenchymal bridge is not a sign of doubling of the PC.

Drawing. On ultrasound, the renal sinus is separated by a complete parenchymal bridge (1, 2). In such cases, excretory urography will help to differentiate between kidney duplication and Bertini column hypertrophy. The double kidney is covered with a common fibrous capsule. Complete duplication involves the presence of two pelvises, two ureters and two vascular bundles. An incompletely duplicated kidney (3) is fed by one vascular bundle; the ureter can be doubled at the top and flow into the bladder with one or two mouths. Doubling of the urinary tract and ureters is a risk factor for the development of pathology (pyelonephritis, hydronephrosis, etc.).

Drawing. On ultrasound, the renal sinus is wide, with a heterogeneous echostructure (1, 2). Against the background of hyperechoic fat, the hypoechoic focus is round in shape (2); with CDK, the interlobar vessels pass through the hypoechoic zone without displacement (3) - this is hypoechoic fat. In obesity, sinus lipomatosis can be mistaken for parenchymal atrophy.

The ureter, minor and major calyces are normally not visible on ultrasound. There are three types of location of the pelvis: intra-, extrarenal and mixed (partially inside the kidney, partially outside it). With an intrarenal structure, the lumen of the pelvis at an early age is up to 3 mm, at 4-5 years - up to 5 mm, in puberty and in adults - up to 7 mm. For extrarenal and mixed types of structure - 6, 10 and 14 mm, respectively. When the bladder is full, the pelvis can increase to 18 mm, but 30 minutes after urination it contracts.

Drawing. Regardless of the filling of the bladder, ultrasound shows a pelvis of mixed (1, 2) and extrarenal (3) location.

Drawing. In children under 1 year of age, the renal sinus is poorly identified on ultrasound; anechoic pyramids can be mistaken for an extended maxillofacial area (1). On ultrasound at the renal hilum, a linear hypoechoic structure resembles a dilated pelvis (2); with color circulation it is clear that these are vessels (3).

Abnormalities in the location of the kidneys on ultrasound

Anomalies in the location of the kidneys occur when the movement of the primary kidney from the pelvis to the lumbar region is disrupted. Almost always the shape of the kidney is changed, and the gate is open forward.

In thoracic dystopia, the kidney is usually part of a diaphragmatic hernia. With lumbar dystopia, the pelvis is located at the level of L4, with iliac dystopia - L5-S1. The pelvic kidney is located behind or just above the bladder. With cross dystopia, the ureter enters the bladder in its usual place, and the kidney is displaced contralaterally.

Drawing. Dystopia of the kidneys in relation to the skeleton: thoracic on the right (1), bilateral lumbar (2), pelvic on the left (3), lumbar on the right and pelvic on the left (4), lumbar double left kidney (5), cross (6).

Drawing. Dystopia of the kidneys in relation to each other and their fusion with each other: fusion of the upper ends (1), lower ends and doubling of the left kidney (2), the middle parts of the pelvic-dystopic kidneys (3), the lateral parts of the pelvic-dystopic kidneys (4), different ends (5), at an angle (6).

Drawing. On ultrasound, the renal bed on the left is empty (1). Both kidneys are located on the right, fused at the poles (2, 3). Conclusion: Anomaly of the relative position of the kidneys - I-shaped double right kidney.

Drawing. Ultrasound in the pelvis (bladder - acoustic window) reveals kidneys connected by a narrow isthmus (1, 3); parenchymal differentiation is preserved, and blood flow can be traced to the capsule (2, 3). Conclusion: Anomaly of the relative position of the kidneys - fusion of the lower poles of the pelvic-dystopic kidneys.

Kidney mobility on ultrasound

Let's mark the level of the upper pole of the kidney on the skin with the patient lying on his stomach and standing. Before re-measuring, ask the patient to jump.

Normally, when inhaling, the kidneys drop by 2-3 cm. In adults, we can speak of pathological mobility of the kidney if on an ultrasound in a standing position the kidney moves by 5 cm. In children, a displacement of 1.8-3% of height indicates excessive mobility, a displacement >3% is an indirect sign of nephroptosis. Nephroptosis is determined by x-ray - this is a movement of the kidney more than 2 times the height of the vertebral body.

How to distinguish nephroptosis from dystopia on ultrasound? Normally, the VA originates from the aorta immediately below the SMA, in lumbar dystopia - near the bifurcation of the aorta, in pelvic dystopia - from the iliac artery.

Drawing. With pelvic dystopia on intravenous urography in the supine position, the ureter is short, the kidney is in the pelvis (1, 2). With nephroptosis, intravenous urography in the supine position reveals the kidney in a typical place (3); in the standing position, the kidney is significantly lowered (4).

Take care of yourself Your Diagnosticer!

Video. Kidneys at an ultrasound lecture by Vladimir Izranov