Anatomy of the Kidneys, Bladder and Urethra Quiz

See Position and Surface Anatomy. Option E is correct because the kidneys are retroperitoneal organs, which means they lie behind the peritoneum, the thin membrane that lines the abdominal cavity and wraps the bowel. They sit against the posterior abdominal wall, one on each side of the vertebral column, roughly between the levels of T12 and L3. The right kidney usually lies slightly lower than the left because the liver pushes it down. Each kidney is wrapped in three layers: a tough fibrous capsule, a layer of perirenal fat and an outer envelope called the renal fascia. The 12th rib crosses the back of each kidney, and the upper pole lies behind the pleura (the membrane around the lung), which matters for procedures and trauma. The retroperitoneal position has practical consequences. Bleeding or infection around a kidney collects behind the peritoneum and can track in a different way from a problem inside the abdominal cavity, and kidney pain is felt in the loin and flank rather than centrally. A simple way to remember it is that the kidneys are the organs behind the bowel: out of the peritoneal sac, up against the back.

• Position: the kidneys are retroperitoneal, lying behind the peritoneum.
• Level: against the posterior abdominal wall, roughly between T12 and L3.
• Consequence: kidney pain is felt in the loin and flank rather than centrally.

D gives the correct posterior wall but the wrong compartment; the kidneys are retroperitoneal, not intraperitoneal. C gives the correct compartment but the wrong wall; the kidneys lie against the posterior, not lateral, abdominal wall. B gives the correct compartment and wall but the wrong vertebral level; adult kidneys usually lie at T12 to L3, not L4 to S1. A gives the correct position but reverses the normal asymmetry; the right kidney is usually lower than the left because the liver displaces it downwards.