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BASIC ANATOMY OF THE URINARY SYSTEM
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The kidneys are located in the retroperitoneum on either side of the spine. The left kidney is slightly higher than the right one and it typically extends from the level of T12 to the level of L3 vertebral body. The adrenal gland is located on top of each kidney. Both the kidney and adrenal gland are surrounded from the inside to the outside by the perinephric fat, the renal fascia (Gerota fascia), and the paranephric fat.
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The kidney is a bean-shaped structure harboring the hilum on the medial side. Through the hilum, the renal artery enters the kidney posterior to the renal vein and anterior to the renal pelvis.
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The internal structure of the kidney, the renal parenchyma, is composed of a superficial cortex and a deep medulla. The medullary pyramids are triangular with the base directed outward toward the cortex and the apex directed inward toward the renal pelvis. The renal columns of Bertin are an invagination of the renal cortex between the medullary pyramids. The tip of the pyramid extends to the collecting system and is called the renal papilla. The renal papilla is surrounded by the minor calyx, which collects the urine coming from the papilla of the renal pyramids. Two or three minor calyces unite to form the major calyx. Major calyces in turn unite forming the renal pelvis, which gives forth the ureter (Fig. 6.1).
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The ureter is a muscular tube, 25 to 30 cm in length. It descends in the retroperitoneum downward and medially in front of the psoas muscle, opposite the tips of the lumbar transverse processes up to the pelvic brim, where it crosses over the end of the common iliac artery or the beginning of the external iliac artery. The ureter then runs along the lateral pelvic wall until it reaches the level of the ischial spine, where it courses anterior and medially to enter the urinary bladder at its posterior inferior surface at the vesicoureteral junction. The ureter has three areas of relative narrowing in its course. These are common sites for stone impaction: at the pelviureteric junction, where it crosses the pelvic brim and at the ureterovesical junction.
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The urinary bladder lies in the pelvis with the peritoneum covering only its superior surface. On its posterior surface, the ureters pass through the bladder wall for 2 cm in an oblique course before they open into the urinary bladder cavity by slitlike apertures. The two ureteric orifices are joined with the interureteric ridge. The openings of the ureters together with the opening of ...