Differential Diagnosis (S. mansoni)

When schistosomiasis affects the bowel, it may closely resemble ulcerative or especially granulomatous colitis. Fortunately, in most parts of the world where schistosomiasis is common, both of these conditions are rare and malignant disease of the large bowel is equally uncommon. A schistosomal granuloma might be mistaken for malignancy, but seldom occurs without other evidence of schistosomal colitis. The granulomas are frequently multiple and vary in size and shape; finding other lesions is additional evidence against malignancy, but follow up after treatment will be necessary. It may be impossible to differentiate amebiasis radiologically: it is more common in the right colon, whereas schistosomiasis is more often seen in the left colon. Polyp formation is virtually unknown in amebiasis but quite frequent in S. mansoni and S. japonicum infections. The real difficulty with colonic disease is that many patients will have both schistosomiasis and amebiasis. The radiological changes in the small bowel may be due to other parasites. The demonstration of calcified eggs by CT, or of the early changes of schistosomal liver disease, will influence the differential diagnosis.

Pulmonary schistosomiasis radiographed during the passage of the cercaria may resemble any pneumonia. During antischistosomal therapy there may be an allergic reaction of the Löffler type, resembling bronchopneumonia, which is constantly varying in distribution, and which resolves within a few days. When there are granulomas and interstitial fibrosis they will require differentiation from all other causes of similar patterns.

The striking dilatation of the main pulmonary artery in advanced cases of cardiopulmonary schistosomiasis will often suggest the correct diagnosis in the proper clinical setting. The many other causes of pulmonary hypertension, as well as left-to-right shunts, pulmonary stenosis, and other entities which can cause pulmonary artery dilatation, will have to be differentiated.

Extreme Calcification in Schistosomiasis mansoni. There is one reported case of schistosomiasis mansoni in a 38-year-old man from Yemen in which there was marked calcification (due to eggs) throughout the small bowel. This could be seen on a plain radiograph and might even have been mistaken for a barium contrast study. CT showed extensive submucosal calcification along the entire length of the small bowel. Biopsy confirmed that this was due to multiple calcified eggs of S. mansoni. There was no evidence of S. haematobium infection.

The liver showed similar advanced curvilinear calcification and this, too, could be seen on a plain abdominal radiograph. CT confirmed that there was extensive periportal egg deposition in the sleeve fibrosis, which is more usually found without many eggs. The only abnormal liver function test was a high (3x normal) serum alkaline phosphatase. The patient was anemic and there was a periperhal eosinophilia (Radhakrishnan et al. 1988).