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l The venous system anastomoses freely throughout the kidney. The arterial supply does not. Thus occlusion of a segmental artery leads to parenchymal infarction, but occlusion of a segmental vein is not problematic because there are many alternate drainage routes. l Anatomic variations in the renal vasculature are common, occurring in 25% to 40% of kidneys. 2

Each renal pyramid terminates centrally in a papilla. Each papilla is cupped by a minor calyx. A group of minor cacalyces join to form a major calyx. The major calyces combine to form the renal pelvis. There is great variation in the number of calyces, calyceal size, and renal pelvis size. The only way to determine pathologic from normal is by evidence of dysfunction. 3

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Anatomy Anatomy of the Lower Urinary Tract and Male Genitalia 8

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Prostate 10