Urinary System

Kidney Function Restoration Program

Kidney Problems Causes and Treatments

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I. KIDNEYS (Figure 12-1)

A. General features. The kidneys are retroperitoneal organs that lie on the ventral surface of the quadratus lumborum muscle and lateral to the psoas muscle and vertebral column. The upper pole of the left kidney is located at vertebral level T12 and is related to the 11th and 12th ribs, the pancreas, the spleen, and the splenic flexure of the colon. The upper pole of the right kidney is located at vertebral level LI and is related to the 12th rib, the liver, the duodenum, and the hepatic flexure of the colon. The right kidney is lower than the left kidney because the liver is located on the right side. The kidneys are covered directly by a fibrous capsule (renal, or true, capsule) that can be stripped readily from the surface of the kidney, except in some pathologic conditions that cause strong adherence because of scarring. The kidneys are further surrounded by the perirenal fascia of Gerota (false capsule), which is important in staging renal cell carcinoma. The perirenal fascia of Gerota defines the perirenal space that contains the kidney, adrenal gland, ureter, gonadal artery and vein, and perirenal fat. Any fat located outside the perirenal space is called pararenal fat. This fat is most abundant in the posterolateral area. In the renal hilus, the following anatomic structures are arranged in an anterior-to-posterior direction: renal vein y renal artery ► renal pelvis.

B. Internal structure

1. The outer cortex is located directly below the renal capsule and extends between the renal pyramids as the renal columns (columns of Bertin).

2. The inner medulla is composed of 5—11 renal pyramids (pyramids of Malpighi), whose tips terminate as 5—11 renal papillae.

3. The collecting system of the kidney includes:

a. 5—11 minor calyces, which are cup-shaped structures that surround each renal papilla b. 2 or 3 major calyces, which are formed by the fusion of minor calyces c. The renal pelvis, which is the main urine collection chamber and is continuous with the ureter at the ureteropelvic junction

C. Vascular supply

1. The renal artery branches into five segmental arteries. Four anterior segmental arteries supply anterior segments of the kidney, and one posterior segmental artery supplies the posterior segment. Segmental arteries have the following clinical importance:

a. Because collateral circulation between segmental arteries (i.e., end arteries) is limited, an avascular line (Brodel white line) between the anterior and posterior

Linea Brodel

Figure 12-1. (A) General features of the kidney, collecting system, and blood supply. (B) IVP of the kidney collecting system. Note that the normal minor calyx is cup-shaped. (C) Arteriogram of the kidney vasculature. A = aorta; Ar- arcuate artery; AS = anterior segmental artery; IL = interlobar artery; ILu = interlobular artery; Ml = minor calyx; MJ = major calyx; P = renal pelvis; PY = pyramid; PS = posterior segmental artery; RA = renal artery. (A adapted with permission from Henrikson, RC, Kaye Gl, Mazurkiewicz JE: NMS Histology. Baltimore, Williams & Wilkins, 1997, p 327; B adapted with permission from Fleckenstein P, Tranum-Jensen J: Anatomy in Diagnostic Imaging. Philadelphia, WB Saunders, 1993, p 282; C adapted with permission from Stevens A, Lowe J: Human Histology 2nd ed. St. Louis, Mosby, 1997, p 277.)

Figure 12-1. (A) General features of the kidney, collecting system, and blood supply. (B) IVP of the kidney collecting system. Note that the normal minor calyx is cup-shaped. (C) Arteriogram of the kidney vasculature. A = aorta; Ar- arcuate artery; AS = anterior segmental artery; IL = interlobar artery; ILu = interlobular artery; Ml = minor calyx; MJ = major calyx; P = renal pelvis; PY = pyramid; PS = posterior segmental artery; RA = renal artery. (A adapted with permission from Henrikson, RC, Kaye Gl, Mazurkiewicz JE: NMS Histology. Baltimore, Williams & Wilkins, 1997, p 327; B adapted with permission from Fleckenstein P, Tranum-Jensen J: Anatomy in Diagnostic Imaging. Philadelphia, WB Saunders, 1993, p 282; C adapted with permission from Stevens A, Lowe J: Human Histology 2nd ed. St. Louis, Mosby, 1997, p 277.)

segments permits minimal bleeding when a longitudinal incision is made. This approach is useful for surgical removal of renal (staghorn) calculi.

b. Ligation of a segmental artery causes necrosis of the entire segment.

c. Supernumerary (aberrant) segmental arteries form during fetal development and persist into adulthood. They may arise either from the renal artery (hilar) or directly from the aorta (polar). Ligation of a supernumerary segmental artery results in necrosis of the entire segment.

2. Interlobar arteries are branches of segmental arteries that enter a renal column.

3. Arcuate arteries are branches of interlobar arteries that travel between the cortex and medulla at the corticomedullary junction.

4. Interlobular arteries are branches of arcuate arteries that travel within the cortex to terminate as afferent arterioles.

D. Clinical considerations

1. Rotation of the kidney. During their relative ascent, the kidneys rotate 90° medially so that the renal hilus normally is oriented medially.

2. Ascent of the kidney. The fetal metanephros is located in the sacral region, although the adult kidneys normally are located at vertebral level T12—L3. The change in location (ascent) results from a disproportionate growth of the embryo caudal to the metanephros.

3. Horseshoe kidney occurs when the inferior poles of the kidneys fuse during fetal development. The horseshoe kidney becomes trapped behind the inferior mesenteric artery as the horseshoe kidney attempts to ascend toward the normal adult location.

4. Duplication of the renal pelvis and ureter occurs when the ureteric bud divides prematurely before it penetrates the metanephric mesoderm.

5. Adult polycystic kidney disease is an autosomal dominant disease in which the kidney is enlarged because it contains multiple large cysts. Clinical findings include: bilateral flank masses, hypertension, renal failure, lumbar pain, recurrent pyelonephritis, hepatic cysts, and berry aneurysms of the circle of Willis.

6. Genitourinary tuberculosis causes small granulomas within the cortex of the kidney, usually near glomeruli. The infection eventually destroys the renal papillae and gives the minor calyces an irregular appearance. Tuberculosis usually proceeds from the kidney toward the urinary bladder. In contrast, schistosomiasis proceeds from the urinary bladder toward the kidney.

7. Chronic pyelonephritis (reflux nephropathy) is caused by reflux of infected urine from the bladder into the kidney (renal pyramids). In children, it usually is associated with repeated bacterial infections as a result of vesicoureteral reflux, a congenital anomaly in which the intramural portion of the ureter is abnormally short.

8. Renal cell carcinoma is the most common type (90%) of solid renal tumor in adults. Its etiology is unknown, but it appears to arise from the proximal convoluted tubule. It is associated with von Hippel-Lindau disease. Renal cell carcinoma is resistant to chemotherapy as a result of the expression of the multidrug resistant (MDR) gene, or P-glycoprotein. It may thrombose to the renal vein or the inferior vena cava. Clinical findings include: hematuria, flank pain, weight loss, left testicular varicocele in males, and flank mass.

9. Kidney trauma is suspected in the following situations: fracture of the lower ribs, fracture of the transverse processes of the lumbar vertebrae, gunshot or knife wound over the lower rib cage, or after a car accident when seatbelt marks are present. Right kidney trauma is associated with liver trauma; left kidney trauma is associated with spleen trauma. Clinical findings include: flank mass or tenderness, flank ecchymosis, hypotension, and hematuria. An absolute indication for renal exploration is the finding of a pulsatile or expanding retroperitoneal hematoma at laparotomy. The first structures that should be isolated during renal exploration are the renal artery and renal vein, which are located superior to the inferior mesenteric artery.

10. Surgical approach. To prevent inadvertent entry into the pleural space, the incision is made below and parallel to the 12th rib. The incision may be extended to the front of the abdomen by traveling parallel to the inguinal ligament.

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Responses

  • robel
    WHAT IS THE function of the malpighi's pyramid IN THE renal system?
    7 years ago

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