Figure 8-1. (A) The major branches of the abdominal aorta. The abdominal vasculature has a fairly robust collateral circulation. Any blockage (X) between the superior mesenteric artery (SM\ at vertebral level L1) and inferior mesenteric artery (IM\ at vertebral level L3) causes blood to be diverted along either or both of two routes of collateral circulation. The first route uses the middle colic artery, which is a branch of the SM artery, which anastomoses with the left colic artery, a branch of the IM artery. The second route uses the marginal artery. CH = common hepatic artery; CI = common iliac artery; CT= celiac trunk; G = gonadal artery; LG = left gastric artery; RA = renal artery; S = splenic artery. T12, L1, and L3 indicate the vertebral levels of the various branches. (B) Arteriogram showing other arteries in the vicinity. 1 = catheter in aorta; 2 = catheter in celiac trunk; 3 = splenic artery; 4 = left gastric artery; 5 = common hepatic artery; 6 = hepatic artery proper; 7= left hepatic artery; 8 = right hepatic artery; 9 = right gastric artery; 10 = cystic artery; 11 = gastroduodenal artery; 12 = right gastroepiploic artery; 13 = left gastroepiploic artery; 14 = posterior superior pancreaticoduodenal artery; 15 = anterior superior pancreaticoduodenal artery. (A adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed. Baltimore, Williams & Wilkins, 1992, p 168; B adapted with permission from Ryan S, McNicholas M: Anatomy for Diagnostic Imaging. London, WB Saunders, 1994, p 156.)
2. Acute mesenteric ischemia most commonly is caused by an embolism within the superior mesenteric artery. Clinical signs include: severe abdominal pain that is out of proportion to the physical findings. There is no evidence of peritonitis. Acute mesenteric ischemia usually occurs in elderly patients who have a history of heart disease and are taking digoxin (a potent splanchnic vasoconstrictor).
3. Gradual occlusion most commonly is seen in atherosclerotic patients, at the bifurcation of the abdominal aorta. It may result in claudication (i.e., pain in the legs when walking) and impotence as a result of the lack of blood to the internal iliac arteries.
A, Azygous venous system
II. VENOUS DRAINAGE OF THE ABDOMEN (Figure 8 2)
Figure 8-2. Diagram of the azygous venous system and the inferior vena cava (IVC). Note that the left gonadal vein (LGV) drains into the left renal vein (LRV). This pathway has clinical implications in males (e.g., left testicular varicocele). The azygous vein provides a route of collateral venous return (arrows) if the IVC is blocked (X). AZ- azygous vein; HAZ= hemiazygous vein; LBCV = left brachiocephalic vein; LCIV= left common iliac vein; RBCV = right brachiocephalic vein; RCIV = right common iliac vein; RGV = right gonadal vein; SVC = superior vena cava.
Abdominal Vasculature 65 RBCV LBCV
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