[Visualization of the inferior mesenteric artery in the ultrasound B image]

Sonographic assessment of splanchnic arteries and the bowel wall

The intestinal wall can be visualized using high resolution transabdominal ultrasound. The normal intestinal wall thickness in the terminal ileum, cecum, and right and left colon is <2mm when examined with graded compression. It is important to appreciate that a contracted intestinal segment can be misinterpreted as a thickened wall. Vascularisation can be mainly displayed in the second hyperechoic layer (submucosal layer) as well as vessels penetrating the muscularis propria. Imaging of the gastrointestinal wall is dependent on the experience of the examiner as well dependent on the equipment used. Acute or chronic inflammation of the intestinal wall is accompanied by increased perfusion of the mesentery, which can be displayed non-quantitatively with colour duplex. In contrast, ischemia is characterised by hypoperfusion of the mesenteric arteries and the bowel wall. The most promising sonographic approach in assessing splanchnic arteries and the bowel wall is combining the analysis of superior and inferior mesenteric inflow by pulsed Doppler scanning (systolic and diastolic velocities, resistance index) with the end-organ vascularity by colour Doppler imaging diminishing the influence of examination technique only displaying bowel wall vascularity. Colour Doppler imaging has been described as helpful in a variety of gastrointestinal disorders, particularly in patients with Crohn's disease, celiac disease, mesenteric artery stenosis and other ischemic gastrointestinal diseases, graft versus host disease and hemorrhagic segmental colitis.