What are the contents of the retroperitoneal spaces?

Anterior pararenal space: Duodenum, pancreas, colon (fluid from pancreatitis or ruptured duodenum may accumulate here)

Perirenal space (Gerota's fascia marks the boundaries): Kidneys, adrenal glands, renal pelvis, ureter, fat (important for staging renal cell cancer)

Posterior pararenal space: Flank stripe
(extraperitoneal fat), no organs