Ischemia and infarction of the small bowel and colon: spectrum of imaging findings.

Mesenteric ischemia presents as an abdominal emergency due to decreased intestinal blood flow secondary to mesenteric arterial vascular hypoperfusion, occlusion, or impaired venous drainage [1]. The small bowel or colon maybe involved. Distinction between intestinal ischemia and infarction sometimes is not considered adequatelyin the interpretative process: the ischemia maybe a transient and a totally reversible event, whereas infarction maybe one of the possible consequences that requires surgical or interventional management. Despite continuing advances in imaging and surgical techniques, early detection of intestinal ischemia before infarction develops remains difficult [2]. Early diagnosis is important to improve survival rates [2, 3]; in most cases of late or missed diagnosis, mortality rate from intestinal infarction is very high, from 60% to 90% [4–6]. Prognosis of an ischemic intestinal insult depends upon clinical factors, such as its acuteness, duration and severity, the presence of collateral vascular circulation, the response of the mesenteric vascular branches and intestinal wall to the injury[7], extent of intestinal involvement, and the timeliness of diagnosis and intervention. From a phase in which the intestinal vascular injurymaybe suspected and the imaging findings of ischemia noted, the severityof mural damage may proceed rapidly to infarction with dire consequences. Differences in bowel wall findings maybe appreciable between small bowel arterial and venous infarctions [8–10]. Radiologic descriptions of intestinal ischemia and infarction reported in the literature are rich [10–13] but not pathognomonic. Currently, there is no report of a direct correlation between bowel wall findings and a confirmed diagnosis of ischemia or infarction. Most literature on this topic is characterized bynonhom ogeneous material and methodologyof study. Some parameters regarding the timing of imaging in which studies are performed, intravenous and/or oral contrast medium administration, dynamics of the acute vascular injury, and the different etiologies (superior or inferior venous or arterial mesenteric vessels, occlusive or nonocclusive event) are sometimes difficult to summarize in a comparative classification. However, diagnostic imaging mayplay a pivotal role in the detection of the degree and severityof intestinal ischemia and assessment for evidence of infarction. In the following sections, imaging findings (wall thickness and enhancement, caliber of intestinal loops, presence of air-fluid levels, intestinal peristalsis, mesenteric arterial and venous vessel viabilities, mural and/or portal/mesenteric pneumatosis) from different method of study(abdominal plain film, sonography[US], and computed tomography[CT]) will be correlated to various phases of intestinal changes from ischemia and infarction due to mesenteric vessels hypoperfusion or occlusion based on experience in our institutions.