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Radiological Diagnosis

The radiographic findings are influenced by the severity and stage of the disease. Many roentgen manifestations of shigellosis are similar to those seen in other inflammatory diseases of the small and large bowel. A large amount of gas may collect in the small and large bowel on plain film examination of the abdomen. Barium examination of the small intestine may show mucosal edema, segmentation, loss of normal fold pattern, hypersecretion, and especially hypermotility with rapid transit time.

In many patients, no radiological changes are observed in the colon on barium enema examination. However, in active, moderately advanced disease, there may be edema of the entire mucosa with spasm and irregularity of the bowel wall. It is difficult to fill the complete colon and terminal ileum by barium enema because of pronounced contractions and tenesmus. Postevacuation radiographs usually show complete elimination of the barium.

In more severe cases of Shigella dysentery, focal ulcerations may be present which are usually not deep and rarely extend into the muscularis (Fig. 19.1). These superficial ulcers may be found throughout the colon but are more prevalent in the rectosigmoid area (Fig.19.2). At this stage, the ulcerated appearance of the colon in bacillary dysentery may radiologically resemble acute generalized ulcerative colitis, with irregular bowel contour, marked spasm, and eventual partial cicatricial stenoses (Fig. 19.3).

In chronic Shigella infections, rapid filling with barium is seen in segments or throughout the entire colon, with loss of haustrations. Transient spasmodic emptyings and reflux fillings may occur and the colon may be rigid and tube-like in some segments. Postevacuation films show segmental puddling of barium with loss of haustral markings.

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Fig. 19.1 (A and B) Bacillary dysentery. Note the finely serrated appearance of the rectum from tiny superficial erosions, which are also in the descending colon. Marked edema of the haustral folds and moderate spasm are noted in the sigmoid colon. (Courtesy of Dr.Wylie Dodds).

Fig. 19.2 Bacillary dysentery. There is marked thickening of the rectal valves due to edema, and there is widening of the presacral soft tissue space. Fine collar-button ulcerations are seen along the posterior aspect of the sigmoid colon. (Courtesy of Dr. Wylie Dodds).

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Fig. 19.3 Bacillary dysentery. (A and B) Films of the filled colon during barium enema show tubular narrowing of the descending and proximal sigmoid colon with multiple small ulcerations and irregular mucosal pattern. There is an area of spasm in the distal descending colon. The rectum and distal sigmoid colon appear normal. (C) Another film taken during the same examination shows that the area of spasm in the distal descending colon has relaxed, permitting visualization of edematous, ulcerated mucosa throughout the slightly narrowed proximal sigmoid and descending colon. (D) Postevacuation film shows the irregular contour and ulcerated, edematous mucosa of the entire left colon. Multiple areas of thumbprinting caused by mucosal edema are seen in the descending colon.

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