Computed tomography of the kidneys

Congenital malformations of the kidneys

The density of the renal parenchyma on native images during computed tomography is about 30 HU. The size of the kidneys is very diverse. If the external contour of the kidney is even, and the parenchyma is evenly weakened, one-sided hypoplasia of the kidney is likely. A reduced kidney is not necessarily a patient.

If the kidney is due to the ileum, it is not always an indication of ectopia. There can be a transplanted kidney. Its vessels are connected to the iliac, and the ureter with the bladder.

The location and the number of renal arteries are very variable. They should be carefully examined to confirm the stenosis, as the cause of renal hypertension. There is a full or partial doubling of the ureter. For a complete doubling of the kidney, doubling of the renal pelvis is characteristic.

Sometimes fatty fiber of reduced density in the gate has a fuzzy border with the surrounding parenchyma of the kidney due to the progress of X-ray stiffness or the effect of partial volume. In this comparison of the adjacent sections will show that only the fatty tissue of the kidneys is visualized. And the true tumor in this example is to the posterior margin of the right lobe of the liver.

Kidney cysts

Cysts in the kidneys of adults are often discovered by chance. They can be located in any part of the parenchyma. Cysts, located near the renal pelvis, resemble hydronephrosis. Benign cysts usually contain a serous clear liquid with a density of -5 to +15 HU. Reinforcement after injection of KB does not occur, because cysts do not have blood vessels. Measurement of cyst density may not always be accurate because of the effect of a particular volume on a given slice or the eccentric window of the area of interest. In this case, only the correct location of the area of interest in the center of the cyst allows one to determine its true density (about 10 HU). In rare cases, when hemorrhage occurs in benign cysts, an increase in the density of its contents is determined on non-intensified images. After the introduction of a contrast medium, there is no change in density.

An increase in density or calcification of renal formations indicates a history of tuberculosis, echinococcal invasion, or renal cell carcinoma. The difference between images before and after contrast enhancement also provides information about the function of the kidneys. With good perfusion, after about 30 seconds, the first phase of accumulation of the contrast medium, which begins with the cortex, is determined. After another 30-60 s, the contrast preparation is excreted into the more distal tubules, causing an increase in the brain substance - a homogeneous amplification of the entire renal parenchyma occurs.

The appearance of kidneys with multiple cysts in children with congenital autosomal recessive polycystosis differs markedly from cysts in adults, which are usually a random finding. Polycystic kidney disease in adults is an autosomal dominant disease, accompanied by multiple cysts in the liver, bile ducts, less often in the pancreas and the presence of aneurysms of the vessels of the brain or abdominal cavity.

Hydronephrosis

Cysts near the renal pelvis can be confused with stage 1 hydronephrosis, which on the native images is characterized by an enlargement of the pelvis and ureter. In the 2nd stage of hydronephrosis, the borders of the renal calyces become indistinct. In 3 stages, atrophy of the renal parenchyma occurs.

To diagnose only nephrolithiasis, computer tomography of the kidneys should not be used, since it is associated with a significant radiation burden on the patient. In nephrolithiasis, as in hydronephrosis, ultrasound is the method of choice.

In the 3 stages of chronic hydronephrosis, the volume of the parenchyma decreases and is defined as a narrow band of tissue, with atrophy developing and the kidney not functioning. In doubtful cases, the detection of an enlarged ureter is distinguished by hydronephrosis from the proximal cyst. Contrast substance accumulates in the enlarged renal pelvis, but not in the cysts.

Solid tumor formation of the kidneys

Contrast enhancement often helps distinguish the effect of a particular volume of a benign cyst from a hypodense kidney tumor. However, the CT image does not contain specific data on the etiology of education, especially when the neoplasm in the kidney parenchyma has fuzzy boundaries. Non-homogeneous enhancement, infiltration of surrounding structures and invasion of the pelvis or renal vein are signs of malignancy.

If the formation is solid, heterogeneous, and contains fatty inclusions, one should think about angiomyolipoma. Benign hamartomas contain fatty tissue, atypical muscle fibers and blood vessels. Often there is an invasion of the tumor into the vessel wall, which leads to intra-tumoral or retroperitoneal bleeding (not shown here).

Kidney pathology associated with blood vessels

If a fresh wound in the abdominal cavity is detected with a penetrating wound or blunt abdominal trauma, a source of bleeding should be determined as soon as possible. Differential diagnosis should include not only rupture of the spleen or disruption of the integrity of a large vessel, but also damage to the kidney. On unresponsive images, the signs of a kidney rupture are the blurriness of the kidney contour in the area of damage and bleeding, as well as the presence of a hyperdense fresh hematoma located in the retroperitoneal space. In this case, the amplified images demonstrate the kidney parenchyma with still good blood supply and stored function.

After extracorporeal shock wave lithotripsy (ESWL), kidney damage sometimes occurs with the formation of small hematomas or leakage of urine from the ureter. If there is persistent pain or hematuria after ESWL, a CT scan should be done. After intravenous administration of contrast medium and excretion of its kidneys, blots of the contrast drug with urine in the retroperitoneal space are determined.

On a CT scan, the kidney infarction usually has a triangular shape in accordance with the angioarchitectonics of the kidney. A wide base is attached to the capsule, and the triangular cone gradually narrows to the pelvis. A typical symptom is the lack of amplification with intravenous administration of contrast medium in both early perfusion and late excretory phases. Emboli usually form in the left heart or in the aorta with its atherosclerotic lesion or aneurysmal enlargement.

If, after injection of the contrast medium in the lumen of the renal vein, a region of reduced density is determined, one can think of aseptic thrombosis or tumor thrombosis in kidney cancer. In the presented case, thrombus spreads to the inferior vena cava.

[1], [2], [3], [4], [5], [6]