The Role of Ultrasonography in Intestinal Amebiasis

Ultrasound has an ever expanding role in the evaluation of the gastrointestinal tract. Knowledge of the normal and abnormal patterns have made it possible to recognize intestinal pathology. The "target", "donut" or "pseudokidney" signs produced by bowel wall thickening are not specific because they can be seen in neoplasms, chronic inflammatory disease, ischemic colitis, intussusception, and parasitic colitis (Fig. 1.47). The typical clinical scenario combines thickening of the colon wall of 8-17 mm with a hepatic abscess. Crohn's disease is the primary differential consideration for right-sided lesions, while alterations in the left colon may suggest ulcerative colitis.

Fig. 1.47 Ultrasound study of amebic colitis, showing the typical image of a "pseudokidney" caused by thickening of the colon wall in amebiasis.

The Role of Computed Tomography in Intestinal Amebiasis

CT is the established gold standard for assessing the presence and complications of amebic colitis and solid organ involvement. Subtle manifestations of grave complications such as perforation can be readily demonstrated. The intestine has limited response to adverse stimuli from infectious agents, ischemia, toxic events, or auto-immune diseases. Typically it responds with edema, hemorrhage, or ulcerations. This pathological morphology is grossly represented as generalized or focal wall thickening, sometimes with pericolic inflammation, which can be well demonstrated on CT (Fig. 1.48).

Fig. 1.48 (A) CT in fulminant amebic colitis. There is marked irregular and hypervascular thickening and ulceration of the sigmoid colon with invasion of the pericolic fat. Moderate cecal distension is present. (B) Water-soluble enema in the same patient shows "collar button" ulcers and an irregular, narrowed colon lumen.