Topography
- Right kidney: roughly ventral to the transverse processes of L1 to L4; its cranial pole contacts the renal impression of the caudate process of the liver.
- Left kidney: somewhat more caudal, roughly L2 to L5.
- Both lie dorsally in the abdomen, outside the peritoneum, wrapped in perirenal fat. They are loosely attached, so they move and can be palpated in most cats.
Structure
- Capsular veins: run under the capsule across the surface of the kidney and converge towards the hilus; they are a characteristic feature of the feline kidney.
- Cortex and medulla: the cortex is often pale or yellowish because of lipid in the tubular epithelium. As in the dog, the pyramids merge into a common renal crest.
- Renal pelvis and hilus, where the renal artery enters and the renal vein and ureter leave.
Clinical relevance
- Size: on a ventrodorsal radiograph each kidney measures about 2 to 3 times the length of the body of L2; on ultrasound, about 3–4.5 cm long.
- Chronic kidney disease: very common in older cats; small, irregular kidneys. It is staged with creatinine and SDMA and is associated with hypertension and hypokalaemia.
- Polycystic kidney disease: inherited (autosomal dominant, PKD1 gene) in Persians and related breeds; multiple cysts detectable by ultrasound and a genetic test.
- Ureteral obstruction: calcium oxalate ureteroliths are common in cats; the obstructed kidney enlarges while the other one is often already atrophied.
- Renal lymphoma: bilateral, often irregular renomegaly.
- Feline infectious peritonitis: pyogranulomas on the renal surface.
- Perinephric pseudocysts: fluid collecting between the capsule and the parenchyma in older cats.
3D model
Parenchyma segmented from the CT of a cat (pixelbeaker model), simplified and registered to the atlas skeleton.