الفهرس 
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Abstract
Acute mesenteric ischemia is a life-threatening condition, with a reported mortality rate of 50–90%,that requires early diagnosis and treatment. Mesenteric ischemia is a serious condition that may come on and worsen quickly.(Aouini Fet al. 2012)
Although mesenteric ischemia is not one of the most commonly encountered entities in the acute care setting, it is associated with a high mortality rate.Thus, rapid and accurate diagnosis is imperative. The variable clinical and radiologic presentations and appearances of mesenteric ischemia pose a challenge to both clinicians and radiologists. Strong clinical-imaging communication and correlation is important to detect, diagnose, and treat this entity in the appropriate time course.( Barmase M, Kang M, Wig J, et al.2011)
Mesenteric ischemia can be either acute or chronic. There are 4 major causes of acute mesenteric ischemia: superior mesenteric artery (SMA) embolus, SMA thrombus, mesenteric venous thrombus, and nonocclusive mesenteric ischemia.While chronic means that the condition and symptoms over a relatively long period of time, and can progress without warning to acute mesenteric ischemia.( Dewitte A, Biais M, Coquin J,et al.2011) Regardless of the cause of the ischemia, The CT findings vary widely depending on the cause and underlying pathophysiolog. The affected small bowel loops may be dilated and fluid filled, as a result of interruption in normal peristalsis and increased secretions.
The wall may be thickened, but in some cases will actually be normal or thinned. Bowel wall thickening is more pronounced in cases of venous thrombosis than in cases of arterial thrombosis. It can mimic many other mesenteric conditions encountered in the acute care setting. A high level of suspicion must exist. (Ritz JP& Buhr HJ.2011) CT findings of acute mesenteric ischemia should be characterized according to the cause , the severity (i.e., superficial mucosal or transmural bowel wall necrosis) and the location of bowel ischemia (i.e., small or large bowel). Superimposed bowel wall infection and the presence of and degree of hemorrhage or perforation may also affect the CT appearances of acute bowel ischemia.(Wiesner W, Khurana2003).
Almost all patients withacute mesenteric ischemia present with severe abdominal pain. In patients with emboli as the cause the onset of pain is usually sudden, whereas patients with thombotic etiology may have a more insidious onset of symptoms. Nausea, vomiting, and diarrhea are alsocommon complaints.( Oldenburg2004)
Angiography has been the reference standard imaging examination; however, significant advancements in computed tomography (CT) scanner technology along with the development of helical CT Scanners have resulted in new applications for CT imaging . In particular, multidetector-row CT (MDCT) technology has dramatically improved the performance of CT by allowing rapid volumetric data acquisition to provide increased longitudinal spatial resolution over a large anatomic volume. from the volume data, retrospective thin or thick sections; sagittal, coronal, or curved multiplanar reformatted images; and CT angiograms with 2D or 3D visualization can be obtained. (Chou CK, et al, 2004)
The development of MSCT technology has overcome past limitations. First, the faster scanning speed increases volume coverage during a single breath-hold and improves the exploitation of contrast medium.
Second, the better spatial resolution results in nearly isotropic voxels allowing reconstruction of high-resolution three-dimensional images with different algorithms. Volume rendering is capable of displaying the visceral vasculature from any external vantage point. Compared to conventional angiography, MSCTA not only delineates vessels but also depicts the anatomical relationship to adjacent structures and allows the evaluation of perfused organs. MSCTA also has become an emerging tool for the pre and postinterventional assessment of vascular anatomy(Wildermuth et al., 2005).
The rapid scanning capability of this technique coupled with IV bolus contrast injection substantially optimizes scan timing to allow both the arterial and venous phases to be imaged, identify important anatomic variants, and evaluate a wide range of pathology.( Tang ZH, er al.2010)
CT can not only aid in the rapid evaluation and diagnosis of mesenteric ischemia but also evaluate other abdominal conditions that may present in a similar manner.( Delhom E, et L.2011).
Recently, the ability of CT to diagnose mesenteric ischemia has been reported to have a sensitivity of approximately 90%. It can also provide alternative diagnoses for patients in whom mesenteric ischemia is suspected. Therefore, nowadays MSCT should probably be used as the first step imaging modality of choice in patients with suspected acute bowel ischemia. (Weisner et al,. 2003).
As the technology continues to mature, that is, higher speed, improved resolution, and multidimensional reformatting, CT is poised to play an increasingly important role in evaluating patients with suspected mesenteric ischemia.( Johnson JO 2012).