The Dying Gut: Identifying Patients with Intestinal Ischemia

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Author: Ashley Grigsby, DO PGY-1M
Indiana University
Originally Published: Modern Resident, February/March 2015

Intestinal ischemia is a serious illness with severe and life threatening complications. The likelihood of developing complications improves with earlier diagnosis. However, early diagnosis can be difficult, especially in the setting of no known risk factors.

Acute mesenteric ischemia is any process that causes hypoperfusion to the small intestine. The large intestine can also become ischemic from hypoperfusion, usually referred to as ischemic colitis.[1] Intestinal hypoperfusion can be due to arterial or venous obstruction from acute embolism, thrombosis or low-flow states.

We all learned in medical school, “abdominal pain out-of-proportion to physical exam” means acute mesenteric ischemia. However, in real-life situations, many emergency department patients presenting with abdominal pain would fit into this category. The question becomes, who gets a workup and who does not? First, a careful history should be performed; about one third of patients with acute intestinal ischemia will have a previous history of embolic event.[1] Patients with peripheral vascular disease, cardiac disease, atrial fibrillation, hypercoaguable states and hypovolemic states are all at increased risk of developing intestinal ischemia.[1]

Acute arterial embolism usually presents with sudden onset pain over the affected bowel area. Patients with chronic peripheral artery disease may thrombose their mesentery and present with worsening chronic postprandial pain. Acute colonic ischemia usually presents with rapid onset of left sided abdomen; however, if large amounts of colon are involved, patients can have diffuse abdominal pain.[1]

Physical examination early in the disease course can be completely normal, however, patients can then progress to distension without peritonitis. Once ischemia has become severe with transmural bowel infarction, peritoneal signs develop. By the time examination is severe, patient may have unstable vital signs, evidence of shock and acidosis.[1]

If the diagnosis is suspected, a workup should be done. Laboratory evaluation should include basic labs and a serum lactate level. The sensitivity for lactate in acute mesenteric ischemia was found to be 86 percent with a specificity of 44 percent. There still remains a minority of patients with true disease who will have a negative lactate; therefore, clinical history and exam should be relied on more than a serum lactate level.[2] Radiologic evaluation should not be delayed due to normal laboratory values when suspicion is high.

Radiologic evaluation should be done in patients without peritonitis. According to the American Gastroenterological Association, patients with peritonitis on exam should have a diagnosis made in the operating room and not await imaging studies.[3] For patients with a less concerning physical exam, CT angiography is the preferred initial test for most patients.[1] However, some patients with colonic ischemia will have normal CT exam and may require urgent sigmoidoscopy to establish diagnosis.[3]

Clinicians need to have a high index of suspicion in order to identify patients with intestinal ischemia. It is important to take a careful history and assess for risk factors in patients with severe, often sudden onset of abdominal pain. When the physician has high suspicion imaging should be performed and not rely on laboratory evaluation. Early consultation with general surgery may also facilitate early intervention, and possibly decrease morbidity associated with this serious disease.

References:

1. Grubel P, Lamont JT. Overview of intestinal ischemia in adults. Up to date. 2014. Access on 13 January 2014. Available from: http://www.uptodate.com/contents/overview-of-intestinal-ischemia-in-adults?source=search_result&search=acute+mesenteric+ischemia&selectedTitle=1~72.
2. Cudnik MT, Darbha S, Jones J, et al. The diagnosis of acute mesenteric ischemia: A systematic review and meta-analysis. Acad Emerg Med 2013; 20:1087.
3. American Gastroenterological Association medical position statement: Guidelines on intestinal ischemia. Gastroenterology. 2000;118(5):95.