Renal capsule and perirenal fascia

The coverings protect the kidney, hold it in position and define clinically important compartments. Immediately on the parenchyma lies the thin, tough fibrous capsule, which is easily stripped from a healthy kidney but adherent in a scarred one; it turns in at the hilum to line the renal sinus. Outside it, the perirenal (perinephric) fat surrounds the kidney and suprarenal gland and extends into the sinus. The renal fascia (Gerota fascia) is a membranous condensation of extraperitoneal connective tissue that encloses kidney, suprarenal gland and perirenal fat; its anterior and posterior layers fuse above the suprarenal gland and laterally, and blend medially with the sheaths of the renal vessels, but they remain open inferiorly around the ureter. Outermost, the pararenal (paranephric) fat lies posterior and lateral to the renal fascia, thickest posteriorly.

The suprarenal gland is separated from the kidney by a thin septum of renal fascia, so the kidney can be removed (or can descend) without disturbing the gland.