Schistosomiasis: An Infrequently Recognized Cause of Rectal Bleed in the Western World

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Intestinal Schistosomiasis is a common cause of chronic intermittent abdominal pain in endemic regions and can often lead to intestinal bleeding. It is due to deposition of eggs in the colonic loose submucosa where they trigger inflammation with subsequent formation of granulomas. We present a case of Schistosomiasis manifesting as rectal bleed. A 35-year-old man from Nigeria came with intermittent rectal bleed for 3 months. Laboratory workup was negative for anemia and peripheral eosinophilia. Colonoscopy was normal except for mild loss of vascularity in the sigmoid and rectum (Figure A and B). Biopsies from here revealed egg deposits in colonic mucosa, morphologically consistent with Schistosoma species. Treatment with praziquantel was initiated. He had resolution of rectal bleeding when seen in follow up visit in 1 month. Clinical manifestations of Schistosomiasis are a result of acute granulomatous response to eggs and not the adult worm. The intensity of such response and resultant inflammation is variable and dependent on antigen load. It can acutely present as cercarial dermatitis and Katayama syndrome. As the granulomatous response to eggs weans over time, the chronic intestinal form of the disease matures as superficial ulcers or hyperplastic polyps, which manifests as non-specific intermittent abdominal pain, diarrhea and rectal bleeding. It is diagnosed by demonstrating the presence of viable eggs in urine or tissue biopsies from endoscopic approaches. Praziquantel is the drug of choice to treat Schistosomiasis and is effective against all species, however kills only the adult worms. It is ineffective against the immature larvae, which would grow into adult worms and cause re-infection, implying drug failure. A common approach to deal with this issue is to re-treat with praziquantel in 3-6 weeks to kill the initially immature larvae that may have matured to an adult one. It is more commonly encountered in immigrants in the western world and should be a consideration with dealing with gastrointestinal bleed among such patients.1495_A Figure 1. Mild loss of vascularity in rectum1495_B Figure 2. Mild loss of vascularity in sigmoid colon