Vascular Assessment of Gastrointestinal Tracts by Color Doppler Ultrasound

Abstract

Transabdominal ultrasound(US) may be regarded as the first imaging procedure for the diagnostic work-up and follow-up of gastrointestinal(GI) tract disease in clinical practice. Unlike computed tomography(CT) and magnetic resonance imaging(MRI), it provides an available, noninvasive, inexpensive method for evaluating the gut without the use of ionizing radiation. Color Doppler US(CDUS) can yield useful information about blood flow in splanchnic vasculature, the bowel wall and its supporting mesentery when used in conjunction with gray-scale US finding and clinical symptoms. For splanchnic vasculature, CDUS can be applied in the diagnosis of portal hypertension-related gastric or duodenal varices and cavernous transformation, midgut malrotation, abdominal aortic dissecting aneurysm, mesenteric ischemia/ aeroportia and arterial-venous shunting. For intramural vasculature, CDUS with state-of-the-art imaging equipment(eg. Superb microvascular image) allows sensitive detection of blood flow in the abnormal bowel wall. Hypervascularization in disease activity of inflammatory bowel disease, infection/inflammation process (eg. bacterial/TB enterocolitis, pseudomembranous colitis, diverticulitis) and abdominal mass (eg. colon cancer, gastrointestinal stromal tumor, actinomycosis, hematoma) can be evaluated by CDUS. Viability of bowel loops can also be evaluated by CDUS and lack or decrease of bowel Doppler signal suggests impending vascular insufficiency (eg. incarcerated hernia, strangulation of bowel, intussusceptions). Diminished vascularity is a specific, although probably not sensitive, sign of bowel ischemia. Although gray-scale US with CDUS should not be considered a replacement of CT/MRI, there is value in a multimodality imaging approach when assessing and following up patients with acute and subacute abdominal symptoms. In this talk, the characteristic sonographic features of the GI disorders will be demonstrated by static images and dynamic cine clips.