Urologic Anatomy

162 Urologic Anatomy The adrenal glands lie within the perirenal (Gerota’s) renal artery. In contrast to the multiple arteries, usually a fascia superomedial to the kidneys, buried within the per- single large adrenal vein exits each gland from its hilum. inephric fat. However, the adrenals are embryologically On the right side, this vein is very short and enters and functionally distinct and are physically separated directly into the inferior vena cava on its posterolateral from the kidneys by connective tissue septa and varying aspect.The adrenal vein on the left is more elongated and amounts of adipose tissue. Thus, in cases of renal ectopia, is typically joined by the left inferior phrenic vein before the adrenal gland is usually located close to its normal entering the superior aspect of the left renal vein. The anatomic position and does not follow the kidney. Simi- adrenal lymphatics in general exit the glands along the larly, in cases of renal agenesis, the adrenal is typically course of the venous drainage and eventually empty into present.The right gland assumes a more pyramidal shape para-aortic lymph nodes. The adrenal medulla receives and rests more superior to the upper pole of the right greater autonomic innervation than any other organ in kidney. The left gland is more crescentic and rests more the body. Multiple preganglionic sympathetic fibers enter medial to the upper pole of the left kidney, or it may even each adrenal along the course of the adrenal vein and lie directly on the renal vessels at the left renal hilum. synapse with chromaffin cells in the medulla. This rich Each adrenal is a composite of two separate and func- sympathetic innervation of the medulla reaches the tionally distinct glandular elements, cortex and medulla. adrenal via the splanchnic nerves and celiac ganglion. In The medulla, which forms the central core of each contrast, the adrenal cortex is believed to receive no adrenal, consists of chromaffin cells derived from the innervation. neural crest and intimately related to the sympathetic The kidneys lie in the retroperitoneum along the nervous system. The cells of the medulla produce cate- borders of the psoas muscle. Gerota’s fascia forms an cholamines, primarily epinephrine and norepinephrine, important anatomic barrier around the kidney and tends which are released directly into the bloodstream through to contain pathologic processes originating from the an extensive venous drainage system. The adrenal cortex kidney. Superiorly, Gerota’s fascia fuses and tapers to dis- is mesodermally derived and completely surrounds and appear over the inferior diaphragmatic surface. Medially, encases the medulla.Three cell layers are identified in the Gerota’s fascia extends across the midline and is con- cortex. The outermost layer is the zona glomerulosa, tiguous with Gerota’s fascia on the contralateral side, which produces aldosterone in response to stimulation by although the anterior and posterior leaves are generally the renin—angiotensin system. Centripetally located are fused and inseparable as they cross the great vessels. Infe- the zona fasciculata and zona reticularis, which produce riorly, Gerota’s fascia remains an open potential space, glucocorticoids and sex steroids, respectively. Unlike the containing the ureter and gonadal vessels on either side. zona glomerulosa, these latter functions are regulated The posterior relations of the kidneys to the abdominal by pituitary release of adrenocorticotropic hormone wall musculature are relatively symmetric.The twelfth rib (ACTH). crosses the upper third of each kidney. Because the left The adrenals are very vascularized. The arterial supply kidney lies more cephalad than the right kidney, the is relatively symmetric bilaterally. Multiple small arteries eleventh rib lies directly posterior to the upper aspect of supply each adrenal gland. The three major arterial the left kidney and not the right kidney. sources for each gland are (1) superior branches from the In contrast to the similarities of posterior anatomic inferior phrenic artery, (2) middle branches directly from relations in each kidney, the anterior relation of each the aorta, and (3) inferior branches from the ipsilateral kidney is significantly different. The right kidney lies 372 162. Urologic Anatomy 373 behind the liver, and it is separated from the liver by directly, usually without receiving other venous branches. reflection of the peritoneum, except for a small area of The left renal vein is generally three times the length of its upper pole, which comes into direct contact with the the right (6 to 10cm) and must cross anterior to the aorta liver’s retroperitoneal bare spot. The extension of pari- to reach the left lateral aspect of the inferior vena cava. etal peritoneum that bridges between the perirenal fascia Lateral to the aorta, the left renal vein typically receives covering the upper pole of the right kidney and the pos- the left adrenal vein superiorly, a lumbar vein posteriorly, terior aspect of the liver is called the hepatorenal liga- and the left gonadal vein inferiorly. ment. Excessive traction on this attachment or the The adult ureter is usually 25 to 30cm long. The ureter hepatocolic ligament during right renal surgery can cause is arbitrarily divided into segments for the purposes of hepatic parenchymal tears. The duodenum is applied surgical or radiographic demonstration.The “abdominal” directly to the medial aspect and hilar structures of the ureter extends from the renal pelvis to the iliac vessels, right kidney. The hepatic flexure of the colon, which also and the “pelvic” ureter extends from the iliac vessels to is extraperitoneal, crosses the lower pole of the right the bladder. For radiographic purposes, the ureter is kidney. divided into three segments. The upper ureter is com- On the left, the retroperitoneal tail of the pancreas and monly described from the renal pelvis to the upper the related splenic vessels are applied directly to the border of the sacrum, the middle ureter from the upper upper to middle portion and hilum of the kidney. Supe- border to lower border of the sacrum, and the lower rior to the pancreatic tail, the left kidney is covered by ureter from the lower border of the sacrum to the peritoneum of the lesser sac and here is related to the bladder, respectively. There are three areas of relative posterior gastric wall. Below the pancreatic tail, the narrowing in the ureter that are of clinical importance: medial aspect of the kidney is covered by peritoneum of ureteropelvic junction, the point where the ureter crosses the greater sac and is related to the jejunum. The lower anterior to the iliac vessels, and the ureterovesical junc- pole of the left kidney is crossed by the splenic flexure of tion. Spontaneous passage of ureteral stones can be ham- the colon, generally in an extraperitoneal position. The pered at these areas of narrowing. The ureters lie on the spleen is separated from the upper lateral portion of the psoas muscle and pass medially to the sacroiliac joints left kidney by peritoneal reflection. However, there is and cross the iliac vessels anteriorly. An important typically a peritoneal extension between the perirenal anatomic landmark for easy identification of the ureters fascia covering the upper pole of the left kidney and the is at the site where the ureters cross anterior to the iliac inferior splenic capsule, called the splenorenal, or lienore- vessels. After crossing the iliac vessels, the ureters swing nal, ligament. Just as with the adjacent and often con- laterally near the ischial spines before passing medially tiguous splenocolic ligamentous attachment, care must be to penetrate the base of the bladder. The ureteral blood taken not to exert undue tension on the splenorenal lig- supply originates from the renal, aortic, iliac, mesenteric, ament during operative procedures on the left kidney to gonadal, vasal, and vesical arteries. Free intercommuni- avoid inadvertent tearing of the spleen. Such tearing may cation between these vessels permits extensive ureteral necessitate splenectomy during left nephrectomy. Both mobilization and transposition. Pain fibers refer stimuli splenocolic and splenorenal ligaments and the contralat- to the T12 through L2 segments, whereas the autonomic eral hepatocolic and hepatorenal ligaments are typically innervation is associated with intrinsic parasympathetic avascular and can be divided sharply with safety. motor and sympathetic vasomotor ganglia.The lymphatic The renal artery and vein typically branch from the drainage is to segmental periaortic and caval nodes. The aorta and inferior vena cava, respectively, to supply each ureter may be drawn medially in retroperitoneal fibrosis kidney. The renal vein is more anterior than the renal and laterally as a result of enlargement of periaortic artery, whereas the urinary collecting system is the most lymph node involvement with tumor or an aortic posteriorly located structure of the renal hilum.The renal aneurysm. It is essential to be aware of the course of the arteries and veins typically branch from the aorta and ureter during aortic and pelvic surgery and in difficult dis- inferior vena cava at the level of the second lumbar ver- sections of adjacent organs. tebral body, below the level of the anterior takeoff of the The cephalad portion of the bladder is attached to superior mesenteric artery. The right renal artery passes the anterior abdominal wall by the urachus, a fibrous behind the inferior vena cava in its course and is consid- remnant of the cloaca that attaches the bladder to the erably longer than the left renal artery. The main renal anterior abdominal wall. The obliterated umbilical artery artery typically divides into four or more segmental in the medial umbilical fold serves as an important land- vessels. The renal arteries are end branch vessels and do mark for the surgeon. It may be traced to its origin from not communicate with each other. This is in contrast to the internal iliac artery to locate the ureter, which lies on the renal venous system, which contains many intrarenal its medial side.

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