CT Angiography of Mesenteric Circulation

Patients are instructed to follow a low residue diet at night before scanning and to fast for at least 4 h on the scanning day. Heavy metal drugs or gastrointestinal barium contrast radiographs are prohibited at least 1 week before scanning. Oral administration of negative contrast agents before scanning improves the image quality. Patients are requested to drink 500–1000 mL of warm water 15–20 min before examination; then, an additional 200–300 mL of water should be consumed while patients lie on the examination bed immediately before scanning to expand the stomach and duodenal ampulla to provide good contrast. Positive contrast should be prohibited because it interferes with the observation of enhanced blood vessels and deteriorate the quality of postprocessing images. Since the distal branches of mesenteric vessels are difficult to visualize with conventional computed tomography angiography (CTA), sublingual administration of nitroglycerin 5 min before scanning in patients with no associated contraindications can significantly improve the visualization of these branches.