Approximately 80% of mesenteric blood flow

supplies the bowel mucosa, making it the most sensitive

to ischemia.

CLINICAL PRESENTATION

...... History

Symptoms are nonspecific and common to many conditions. Abdominal pain, nausea, vomiting, and diarrhea are

frequently seen. Any patient older than 50 years with risk

factors ( eg, atrial fibrillation) who experiences acute onset

abdominal pain lasting >2 hours should be suspected of

having acute mesenteric ischemia. Pain out of proportion

to the physical examination is very concerning for mesenteric ischemia. Late findings include peritonitis ( eg, pain

with movement), fever, weakness, and altered mental

status.

Patients with chronic mesenteric ischemia will give a

history of "abdominal angina'' or pain after eating. This is

due to narrowing of the mesenteric artery usually associated

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CHAPTER 32

with chronic atherosclerosis. With eating there is increased

demand for blood flow, causing a relative ischemia until

demand is lowered. These patients go on to have thrombotic occlusion of their narrowed vessels, presenting then

with the common acute symptoms .

...... Physical Examination

Early physical findings may be nonexistent or nonspecific. A patient complaining of extreme pain who has an

essentially normal abdominal exam (especially no pain

on palpation) should prompt consideration of mesenteric ischemia. If not diagnosed at this stage, the ischemia

progresses to necrosis and perforation. The physical

examination will then reveal abdominal distension and

peritonitis. Hemoccult positive stools are found in only

25% of cases.

DIAGNOSTIC STUDIES

...... Laboratory

Lab testing is usually nonspecific and therefore of little

help ruling in or excluding the diagnosis. The white blood

cell count is frequently high, but this is nonspecific. There

is a lack of consensus on the role of lactic acid. It has

100% sensitivity if there is bowel infarction; however, it

may be normal early. If elevated at presentation, it pre ­

dicts a higher morbidity and mortality and should prompt

an aggressive search for ischemia. An electrocardiogram

should be performed to diagnose atrial fibrillation .

..... Imaging

The classic reported finding on plain radiographs is

"thumb-printing;' representing bowel wall thickening and

edema.