In mild ischemic colitis, mucosal disease may lead to diarrhea, which may be bloody. In severe colitis, transmural damage and perforation can result. Sparing of the rectum is typical. If there is no gross blood and occult blood testing is negative, a 24-hour stool specimen should be analyzed for weight and fat to document diarrhea and determine fat content. Documenting diarrhea is important because stool frequency can be mistaken for diarrhea when stool weight is actually normal.
Stools typically are bulky, with a foul odor.
Diagnostic Tests Quantitative fecal fat stool analysis is usually necessary to determine fat content. Although many experts recommend a 72-hour stool collection for fat and weight, this is often unnecessary and impractical in both outpatient and hospital settings. Patients should maintain a regular diet, trying to consume at least 100 g of fat daily. The two most common causes of steatorrhea in the United States are celiac sprue and pancreatic insufficiency, which is usually a result of chronic pancreatitis. When pancreatic insufficiency appears likely, as in cases of chronic alcoholism, a trial of pancreatic enzymes is often reasonable before extensive diagnostic tests are performed.