A negative or neutral oral contrast, such as low-density barium sulfate or water, has been advocated to distend the small bowel and better evaluate the bowel wall for thickening and enhancement; however this may not be possible in the acute setting [30]. Both arterial and portal venous phases should be included as part of the protocol to assess both arterial and venous patency [25,30,31]. Three-dimensional (3-D) rendering may also assist in evaluating the vasculature and should be performed [24,32]. A noncontrast phase is typically obtained as part of the CTA and may be helpful in identifying intramural hemorrhage, atherosclerotic calcifications, and to serve as baseline for assessing wall enhancement; however, several studies have shown that obtaining the noncontrast phase may not be required for accurate acute ischemia diagnosis [25,31,33-35]. CT imaging of the abdomen and pelvis also allows accurate evaluation of the entire gastrointestinal and genitourinary tract, helping to exclude most of the other causes of acute and chronic abdominal pain, including cholelithiasis, cholecystitis, pancreatitis, appendicitis, diverticulosis with or without diverticulitis, and nephrolithiasis. Vascular CT findings include arterial stenosis, embolism, thrombosis, arterial dissection, and mesenteric vein thrombosis. Nonvascular CT findings include bowel-wall thickening, hypoperfusion and hypoattenuation, bowel dilatation, bowel-wall hemorrhage, mesenteric fat stranding, pneumatosis intestinalis, and portal venous gas. Quantitative methods of assessing bowel enhancement may also add value in identifying ischemic bowel [36]. Imaging of Mesenteric Ischemia CTA is also preferred in patients with renal insufficiency with GFR under 30 who have suspected acute ischemia as benefits of a fast and accurate diagnosis will generally outweigh risks associated with potential risk of contrast- induced nephropathy [37,38].
Imaging of Mesenteric Ischemia. A negative or neutral oral contrast, such as low-density barium sulfate or water, has been advocated to distend the small bowel and better evaluate the bowel wall for thickening and enhancement; however this may not be possible in the acute setting [30]. Both arterial and portal venous phases should be included as part of the protocol to assess both arterial and venous patency [25,30,31]. Three-dimensional (3-D) rendering may also assist in evaluating the vasculature and should be performed [24,32]. A noncontrast phase is typically obtained as part of the CTA and may be helpful in identifying intramural hemorrhage, atherosclerotic calcifications, and to serve as baseline for assessing wall enhancement; however, several studies have shown that obtaining the noncontrast phase may not be required for accurate acute ischemia diagnosis [25,31,33-35]. CT imaging of the abdomen and pelvis also allows accurate evaluation of the entire gastrointestinal and genitourinary tract, helping to exclude most of the other causes of acute and chronic abdominal pain, including cholelithiasis, cholecystitis, pancreatitis, appendicitis, diverticulosis with or without diverticulitis, and nephrolithiasis. Vascular CT findings include arterial stenosis, embolism, thrombosis, arterial dissection, and mesenteric vein thrombosis. Nonvascular CT findings include bowel-wall thickening, hypoperfusion and hypoattenuation, bowel dilatation, bowel-wall hemorrhage, mesenteric fat stranding, pneumatosis intestinalis, and portal venous gas. Quantitative methods of assessing bowel enhancement may also add value in identifying ischemic bowel [36]. Imaging of Mesenteric Ischemia CTA is also preferred in patients with renal insufficiency with GFR under 30 who have suspected acute ischemia as benefits of a fast and accurate diagnosis will generally outweigh risks associated with potential risk of contrast- induced nephropathy [37,38].