Veterinary Ultrasound Renal Anatomy
Greetings Scan Squad!
In last week’s edition of The Probe-Cast, we reviewed a case of renal dysplasia in a 5 month old Golden Retriever. The architecture of this kidney was very abnormal with no normal tissue visible (see below). Subsequently, a request to review the ultrasonographic appearance of normal renal architecture was made by one of our readers. So let’s get into it!
Below, there are two images of an ultrasonographically normal left kidney. The top image shows the kidney in longitudinal view and the bottom image shows the kidney in transverse view. For visualisation purposes, it can help to compare the kidney to a cut tomato!
The kidneys are surrounded by a capsule (the skin of the tomato). On ultrasound, this is usually visualised as a hyperechoic (bright) rim surrounding the renal tissue. The arrow in the first image is pointing to the capsule.
Adjacent to the capsule is the renal cortex (the flesh of the tomato). The cortex contains the glomeruli and convoluted tubules. It should be uniformly echogenic (the same ‘colour’ throughout) and hyperechoic to the medulla.
Next, the inner portion of the kidney corresponds to the medulla (the seeds of the tomato). This area contains the renal pyramids and should be hypoechoic (dark) to the renal cortex. It is the margin between the cortex and medulla where you assess the corticomedullary junction (CMJ). A reduction in CMJ may correspond to renal disease.
Finally, the renal pelvis (the core of the tomato). This is the central collecting system, where urine collects before entering the ureters for transport to the urinary bladder. As a result, this area should be anechoic (without echo = black) in a normal patient because it contains fluid. Minimal dilation of the pelvis should be present and a normal ureter will not usually be visible. We delve into how to measure the renal pelvis as well as normal measurements in our guide book.
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The above image depicts the left kidney in longitudinal view and the below image shows the kidney in transverse view. The arrow is indicating the renal capsule. 1. Cortex 2. Medulla 3. Renal pelvis.
