Colon

In patients with megacolon, the outstanding symptom is chronic obstipation, with bowel movements occurring at intervals from 8 days to 5 months. Large boluses of desiccated feces may become impacted in the dilated, atonic rectosigmoid colon, leading to inflammation and stasis ulceration. Another serious complication of megacolon is sigmoid volvulus, which occurs in approximately 10% of patients and is often the presenting manifestation of the disease.

In the colon, the chief radiographic manifestations are striking elongation and dilatation, especially of the rectosigmoid and descending colon (Fig. 4.16). Changes are often readily identified on plain radiographs, where large fecaliths may be seen within a markedly dilated, often redundant colon (Fig. 4.17). A grossly distended splenic flexure or even a redundant sigmoid loop may at times slightly elevate the left hemidiaphragm on plain films of the chest and abdomen (Fig. 4.18). The appearance simulates the splenic flexure syndrome.

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Fig. 4.16. (A)Chagas' megacolon in an adult Brazilian man at necropsy, showing massive dilatation and elongation of the rectosigmoid and distal descending colon. The proximal colon is nearly normal in caliber. AFIP 68-3269-1. (Courtesy of Dr. Clovis Simao, Sao Paulo). (B) Section through a Chagas' megacolon showing the great diameter of the intestinal lumen and the relatively thin intestinal wall. AFIP 69-6534.

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Fig. 4.17 (A) Chronic Chagas' megacolon with massive retained feces throughout a grossly dilated colon opacifying virtually the entire abdomen. This 51 year-old Brazilian man had progressive constipation for more than 14 years despite two previous partial resections of the colon. Following this examination, the entire colon was removed after it was emptied of fecaliths. The colon measured 10 cm in diameter and contained numerous small mucosal ulcers and secondary inflammation. (Courtesy of Dr. Clovis Simao.) (B) The wall was not thickened uniformly, being thin in some places and thick in others. AFIP 69-7469.