Overview
The equine kidneys (renes) have a smooth surface. Inside, the lobes are fused and the papillae form a common renal crest (crista renalis) that drains urine into the renal pelvis. Two long terminal recesses (recessus terminales) extend from the pelvis towards the poles. The mucosa of the pelvis and proximal ureter has mucous glands, so normal equine urine is viscous and cloudy, with mucus and calcium carbonate crystals.
Topography
- Right kidney: shaped like a playing-card heart; further cranial, ventral to the last two or three ribs and the first lumbar transverse process. Its cranial pole sits in the renal impression of the liver and touches the base of the caecum and the pancreas.
- Left kidney: bean-shaped, longer and narrower; further caudal, ventral to the last rib and the first lumbar transverse processes. The nephrosplenic ligament joins it to the spleen.
- Both are retroperitoneal and surrounded by perirenal fat.
Clinical relevance
- Rectal palpation: the caudal pole of the left kidney and, next to it, the nephrosplenic ligament can be reached; the right kidney usually cannot.
- Acute kidney injury: severe dehydration (colic, colitis, prolonged exercise), non-steroidal anti-inflammatory drugs, which can cause renal crest necrosis, aminoglycosides and myoglobin from rhabdomyolysis damage the tubules.
- Chronic kidney disease: weight loss, polyuria, polydipsia and sometimes ventral oedema; the kidneys look small and echogenic.
- Urolithiasis: stones are made of calcium carbonate; renal and ureteral stones are less common than bladder stones.
- Ultrasound: the right kidney is examined through the last right intercostal spaces and the left one through the left flank, next to the spleen.