Mesenteric Ischemia

Ischemic disease of the intestines (small bowel is most common) can be hyperacute, chronic recurrent, or acute on chronic. The classic symptoms and signs attributed to ischemia are actually those of infarction. Diagnosis after infarction is associated with high mortality. Mesenteric ischemia should be considered for patients at risk, such as elderly patients with vascular disease or atrial fibrillation and those who have severe abdominal pain that cannot be adequately explained.

Causes

Mesenteric ischemia is caused by the narrowing or blockage of one or more of the three mesenteric arteries. It can be caused by a blood clot that travels through the bloodstream and blocks one of the mesenteric arteries. A blood clot that breaks away and travels through the bloodstream is called an embolus. This type of acute mesenteric ischemia is life threatening because the blood flow to the intestine is cut off completely, which can cause the intestine to die if not treated immediately.

Symptoms

Symptoms vary depending on location.

• Superior mesenteric artery embolism (50%): acute onset of severe, poorly localized, unrelenting abdominal pain followed by nausea, vomiting, and diarrhea. Patients usually have a history of cardiovascular disease (myocardial infarct, dysrhythmia, or valvular disease), a previous embolism ++, or evidence of embolism elsewhere ++.
• Superior mesenteric artery thrombosis (25%): gradual onset of abdominal pain. Patients may have a history of intestinal angina (postprandial abdominal pain relieved by vomiting), weight loss, and diarrhea or a history of vasculitis, prothrombic disorder, or atherosclerosis.
• Nonocclusive mesenteric ischemia (20%): history of low flow state (sepsis, congestive heart failure, hypotension, or previous treatment with vasopressors, digoxin, or betablockers). Abdominal pain is typically of gradual onset.
• Mesenteric vein thrombosis (5%): progressive onset of abdominal pain, nausea, and vomiting and history of venous thrombosis +++.

Signs

• Pain is classically out of proportion to physical findings.
• Abdominal examination varies depending on the stage of ischemia. Often, physical findings arise late in the disease and range from mild localized or generalized tenderness to peritoneal signs. Occult blood may precede other signs, but its absence does not rule out the diagnosis.
• Usually afebrile with stable vital signs until becoming hypovolemic or septic.

Treatment

Treatment of chronic mesenteric ischemia usually requires surgery. The blockage in the involved arteries is removed, and the arteries reconnected to the aorta. Alternatively, a bypass around the blockage, usually with a prosthetic plastic tube graft, is performed.

Acute mesenteric ischemia is a surgical emergency. An operation is performed, and the clot removed from the artery. In some cases, a bypass must also be performed. As an alternative to surgery sometimes a stent may be inserted to enlarge the blockage of the mesenteric artery. This is a new technique and should only be performed by experienced physicians.