Diagnosis

Acute intestinal ischemia is a life-threatening surgical emergency, yet can be a difficult diagnosis to make, with delay contributing directly to infarction.

The majority of cases are diagnosed more than 12 hours after the onset of symptoms. Delayed diagnosis accounts for the majority of malpractice claims involving acute mesenteric ischemia in the United States. Diagnosis depends on a high index of suspicion. The main presenting feature is the combination of severe abdominal pain out of proportion to the clinical findings, as discussed above.

Serum levels of lactate and leucocytes are elevated in the majority (65% to 90%) of patients to greater than 50 U/L and 15000/mL, respectively.

Hyperamylasemia is seen in just under half the patients with acute mesenteric ischemia. Elevation of serum inorganic phosphate levels have been proposed as a marker of mesenteric ischemia, as it is extensively found in gut, but this only occurs in 15% to 33% of such patients.

However, in those patients who did have elevated phosphate levels, it predicted extensive injury and poor prognosis. The fibrinolytic marker D-dimer is elevated in thrombo-embolic occlusion of the SMA, although levels are also raised in other conditions of acute bowel ischemia such as strangulation or ruptured aortic aneurysm.

Animal studies have suggested intestinal fatty acid binding protein (I-FABP) as a serum marker reflecting bowel ischemia. Early human studies show promise, as patients with ischemic bowel disease demonstrate significantly higher I-FABP levels than either healthy subjects or patients with acute abdominal pain. Patients with mesenteric infarction had the highest serum I-FABP levels.

Plain radiographs of the abdomen may reveal nonspecific bowel dilatation or, in MVT, wall edema (thumbprinting); or gas in the bowel wall or portal vein. Unfortunately they are not helpful in most cases.

Mesenteric angiography will confirm the diagnosis of arterial occlusion but at the cost of delay in treatment. If there are clear abdominal signs of peritonitism, urgent laparotomy without angiography is the best course of action. In the remainder of patients suspected of acute intestinal ischemia with-out abdominal signs, angiography is indicated with lateral views of the visceral aorta and its branches.

In acute SMA thrombosis, there is usually no visualization of the entire artery because of the ostial nature of the disease, although delayed views may show slow filling of the distal SMA. SMA embolization usually allows visualization of the proximal artery to just beyond the level of the middle colic artery.

Date: 2014-12-29; view: 1081