A 70-year-old man undergoes resection of an abdominal aortic aneurysm. Two days later he has drainage of dark blood per rectum. and colonic ischemia is suspected. To establish the diagnosis, it is most appropriate to order
a. The most serious gastrointestinal complication is ischemia of the left colon and rectum.
b. The incidence of transmural colonic ischemia after aortic reconstruction is between 0.6% and 2%.
c. In patients with rupture, this complication rate can be as high as 30%.
d. Intestinal ischemia develops when critical hypogastric arteries are not revascularized or when a patent IMA is ligated in the setting of superior mesenteric artery or bilateral hypogastric artery occlusion.
e. Improper ligation of the IMA too far from the aneurysm wall can interfere with the collateral blood supply to the rectosigmoid and lead to ischemia.
f. Postoperative hypotension and hemodynamic instability are contributory factors..
g. The first indication of bowel ischemia may be a substantial IV fluid requirement in the first 8 to 12 hours after the operation.
h. Diarrhea, usually bloody, typically follows within 48 hours.
j. This typically reveals mucosal changes appearing abruptly between 10 and 20 cm above the anal verge.
k. If necrosis is limited to the mucosa, treatment can be conservative with bowel rest, antibiotics, and fluid resuscitation.
l. However, if the muscular layers are involved, segmental strictures may develop that eventually require resection.
m. Full-thickness necrosis on sigmoidoscopy or signs of peritoneal irritation necessitate urgent reoperation with resection of all ischemic bowel .