The Kidney (Gross Anatomy)

Key points

• • The kidneys are bean-shaped organs lying behind the peritoneum on the back wall of the abdomen, with the right kidney a little lower because of the liver above it.
• • Each is wrapped in three layers: a tough fibrous capsule, then a cushion of perirenal fat, then the renal fascia that anchors it.
• • On its inner border is the hilum, where the renal vein leaves in front, the renal artery is in the middle, and the ureter leaves behind (front to back: vein, artery, ureter).
• • Cut across, the kidney shows an outer cortex and an inner medulla of pyramids whose tips drain urine into the calyces and then the renal pelvis.
• • The renal arteries come straight from the aorta and divide into segmental end-arteries with little collateral flow, so occlusion of a segmental artery can infarct that segment.
• • The kidneys sit against the last ribs at the back, so they can be injured in a lower rib fracture or a blow to the loin.