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Kidney - Sonography

We examine kidneys in position on patients back or on the hip (right kidney on the left hip and vice versa). Both kidneys are better displayed during inspiration.

 

In a kidney we see hypoechogenic parenchyma with pyramids and hyperechogenic central part. We examine in both sagittal and transverse plain. Transverse cut enables us to see kidney hilum with renal artery and vein.

 

Proportions:

Kidney length: 10-12cm

Kidney width: 4-6cm

Parenchyma width : 13-25mm

 

We display right kidney in sagittal plain often together with neighbouring liver tissue. This is very important for evaluation of liver echogenity. Healthy liver tissue has the same echogenity as kidney parenchyma. Higher echogenity (which means brighter appearance) of the liver tissue speaks for steatosis.

 

Kidney - sonography

Longitudinal cut through the right kidney with marked proportions. Neighbouring liver

tissue is brighter than renal parenchyma and therefore probably steatotic.

 

 

Parenchymal bridge – This is clinically not a very important finding. It appears as a dark hypoechogenic line leading through the bright centre of the kidney.

 

Kidney parenchymal bridge - sonography

Parenchymal bridge

 

 

Dromedary hump – It is a thickened mass of renal parenchyma in left kidney near the lower part of the spleen. It is a normal finding by 10% examined patients. It could be sometimes mistaken for a tumour.

Kidney dromedary hump - sonography

Dromedary hump - Parenchyma of the left kidney is broader in its lateral part.

 

 

Renal cysts – They are regular round anechogenic bearings. Very often we find parenchymal and parapelvic cysts. Parapelvic are located in the central part of the kidney and could be easily confused with dilatation of the pelvic tract in hydronephrosis.

 

Renal cyst - sonography

Renal cyst - It is the big round object near the kidney pole.

 

 

Pyelonephritis – Kidney is enlarged, it has higher echogenity of its parenchyma (these are non-specific signs of kidney damage which also appear by glomerulonephritis, amyloidosis, etc.).

 

 

Degenerative processes – The parenchyma becomes thinner. These processes are often connected with angionephrosclerosis. The sclerosis is displayed as short hyperechogenic lines in renal parenchyma above the pyramids.

 

 

Hydronephrosis – We find dilatation of renal pelvis and possible caliceal distension as well. It seems as large hypoechogenic objects in central part of the kidney. From dilated veins they can be distinguished by duplex sonography which would show blood flow in the veins. Differentiation from parapelvic cysts could be sometimes very difficult.

Hydronephrosis has 3 stages according to sonography:

 

1. Pelvic dilatation

2. Pelvic dilatation + caliceal enlargement (+ possible little parenchymal reduction)

3. Pelvic dilatation + caliceal enlargement + parenchymal atrophy

 

Hydronephrosis - sonography

Hydronephrosis- In this picture dilatation of the pelvis and calices is visible.

However, renal parenchyma does not seem to be too atrophic.

 

 

Nephrocalcinosis – Imaging of hyperechogenic concrements is often quite difficult (sometimes nearly impossible in hyperechogenic renal centre). It is important to find hypoechogenic shadow which they create.

 

Nephrocalcinosis - sonography

Nephrocalcinosis - We see two concrements (marked by red circles), which cannot be well distinguished from the hyperechogenic centre of the kidney. However, they form visible cone shadows.

 

 

Kidney infarctions – Kidney ischaemia appears as a triangular hypogenic lesion in parenchyma

with its basis near the renal capsule.

 

 

Kidney tumors – These are irregular anisoechogenic objects growing from the parenchyma. They can have a cystic element.

 

Kidney tumor - sonography

Kidney tumor -In this case quite regular mass with echogenity similar to kidney

parenchyma grows from the upper kidney pole and causes its local enlargement.

(In this case it would be easy to mistake it for a renal cyst)

 

 

Angiomyolipoma – This is a benign tumor which can be best distinguished in its first stages of growth when it looks like small hyperechogenic bearing. As it grows it becomes less echogenic and therefore more similar to malignant tumours.

 

Angiomyolipoma - sonography

Angiomyolipoma - In two US pictures we can see

a round bright object in renal parenchyma.

 
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MUDr. Jiří Štefánek  autor: MUDr. Jiří Štefánek
  kontakt: jiri.stefanek@seznam.cz
  zdroje: základní zdroje textů