Gross and Laparoscopic Anatomy of the Upper Urinary Tract and Retroperitoneum

Overview

The upper urinary tract is contained within the retroperitoneum. The retroperitoneal space is bound by the diaphragm superiorly; posteriorly and laterally by the musculature of the body wall; anteriorly, by the peritoneal envelope; and inferiorly, it is contiguous with the pelvis. The kidneys and ureters lie within the retroperitoneum together with the adrenal glands, as well as significant vascular, lymphatic, and neural structures (see Fig. 2.1). The anterior retroperitoneum also contains the duodenum, pancreas, and portions of the ascending and descending colon, all in close proximity to the upper urinary tract.

The Kidneys

The kidneys are paired, reddish-brown, solid organs that lie deep in the posterior retroperitoneum, on either side of the spine and the great vessels — aorta and inferior vena cava(see Fig.2.2). An individual normal kidney weighs approximately 150 g in an adult man, approximately 135 g in an adult woman. The normal kidney is 10–12 cm in vertical length, 5–7 cm in transverse width, and approximately 3 cm in anteroposterior thickness. The right kidney tends to be shorter in vertical dimension and sometimes wider than the typically longer, more narrow left kidney. This discrepancy is attributed to the

effect of the hepatic mass on the right side, which also tends to push the right kidney to a slightly lower position in the right retroperitoneum, compared to the left kidney on the opposite side.

The kidneys are the organs of urinary excretion, playing a central role in fluid, electrolyte, and acid-base balance; they also have important endocrine functions,including roles in vitamin D metabolism and production of renin and erythropoietin. The kidneys are highly vascular organs, receiving one fifth of the total cardiac output via the renal arteries, which represent major lateral branches from the upper abdominal aorta (see Figs. 2.2 and 2.3).

The substance of each kidney, or renal parenchyma, is friable, but contained by a relatively tough fibroelastic renal capsule. This capsule is capable of holding sutures for renal reconstructive surgery. This capsule can be surgically stripped away from the underlying parenchyma, or elevated by subcapsular hematoma. The renal cortex forms the outer layer of the renal parenchyma, surrounding the central tissue of the renal medulla. The renal medulla does not represent a contiguous layer, but rather consists of multiple conical segments, known as the renal pyramids. The rounded apex of each pyramid is the renal papilla, and points centrally into the renal sinus, where it is cupped by an individual minor calyx of the renal collecting system. The base of each medullary pyramid roughly parallels the external contour of the kidney. The renal cortex extends centrally between individual

Scale—1 division = 30 mm.

Figure 2.1. the retroperitoneum exposed, with gerota’s fascia removed. 1, diaphragm. 2, inferior vena cava. 3, right adrenal gland. 4, celiac artery (upper pointer) and celiac autonomic plexus (lower pointer). 5, right kidney. 6, right renal vein. 7, gerota’s fascia. 8, Pararenal retroperitoneal fat. 9, Perinephric fat.10,right gonadal vein (upper pointer) and right gonadal artery (lower pointer). 11, lumbar lymph nodes. 12, retroperitoneal fat. 13, right common iliac artery. 14, right ureter. 15, sigmoid colon. 16, Esophagus. 17, right crus of diaphragm. 18, left inferior phrenic artery.19, left adrenal gland (upper pointer) and left adrenal vein (lower pointer). 20, superior mesenteric artery (upper pointer) and left renal artery (lower pointer). 21, left kidney. 22, left renal vein (upper pointer) and left gonadal vein (lower pointer). 23, aorta. 24, Perinephric fat. 25, aortic autonomic plexus. 26, gerota’s fascia (upper pointer) and inferior mesenteric ganglion (lower pointer).27, inferior mesenteric artery.28, aortic bifurcation into common iliac arteries.29,left gonadal artery and vein.30,left ureter. 31, Psoas muscle. 32, cut edge of peritoneum. 33, Pelvic cavity (reprinted with permission from Kabalin1 copyright Elsevier 2002).

pyramids. These interpyramidal cortical extensions are known as the columns of Bertin, and through these pass the smaller branches of the renal arteries and veins as they enter and exit the renal parenchyma. On gross inspection, the renal cortical tissue is lighter in coloration than the medulla, and microscopically most remarkable for the presence of the renal glomeruli. Each glomerulus consists of a complex spherical arrangement of arterial capillaries surrounded by the glomerular (Bowman’s) capsule. This is

Figure 2.2. the retroperitoneum exposed, with the kidneys and adrenals sectioned and the inferior vena cava removed.1,inferior vena cava. 2, diaphragm. 3, right inferior phrenic artery. 4, right adrenal gland.5, celiac artery (upper pointer) and superior mesenteric artery (lower pointer). 6, right kidney. 7, right renal artery (upper pointer) and right renal vein (lower pointer).8,lumbar lymph node.9,transversus abdominis muscle covered with transversalis fascia. 10, right ureter. 11, anterior spinous ligament. 12, inferior vena cava. 13, right common iliac artery. 14, sigmoid colon. 15, right external iliac artery. 16, Esophagus. 17, left adrenal gland. 18, celiac ganglion. 19, left kidney. 20, left renal artery (upper pointer) and left renal vein (lower pointer). 21, left renal pelvis. 22, aorta. 23, aortic autonomic nervous plexus. 24, inferior mesenteric ganglion.25,left ureter.26,inferior mesenteric artery. 27, Psoas muscle (reprinted with permission from Kabalin1 copyright Elsevier 2002).

the microscopic junction where the urinary filtrate leaves the arterial stream and enters the urinary flow. From the glomerulus, the urinary filtrate travels through a lengthy series of microscopic channels, beginning with the proximal convoluted tubule,to the so-called loop of Henle, to the distal convoluted tubule, and finally to the collecting tubules and collecting ducts, traversing the renal medulla to the renal papillae to eventually drain urine into the gross renal collecting system. These multiple tubular channels predominate in microscopic examination of the normal renal parenchyma (see Fig. 2.4).

The renal parenchyma surrounds a central space, the renal sinus, opening anteromedially, and through which the major arterial and venous

Figure 2.5. (a) anterior view of gerota’s fascia on the right side, split over the right kidney, and showing the inferior extension enveloping the ureter and gonadal vessels. (b) Posterior view of

a

gerota’s fascia on the right side, rotated medially with the contained kidney, ureter, and gonadal vessels (reprinted with permission from Kabalin1 copyright Elsevier 2002).

Quadratus lumborum

Posterior

Figure 2.8. rotational axes of the kidneys.

(a) transverse view showing approximate 30° anterior rotation of the (left) kidney from the coronal plane, relative positions of the anterior and posterior rows of calyces, and location of the relatively avascular plane between the anterior and posterior renal segmental circulation. (b) coronal view showing the inward tilt of the upper poles of the kidneys. (c) sagittal view showing anterior displacement of the lower pole of the (right) kidney (reprinted with permission from Kabalin1 copyright Elsevier 2002).