Although the chronic stage of proliferation within tissues is distinctive in the different forms of schistosomiasis, a granulomatous reaction to the eggs and chemical products of the schistosome occurs in all forms of the disease. Schistosoma haematobium commonly involves the distal bowel and the bladder, as well as the prostate gland and seminal vesicles. Bladder calcification and cancer may ensue. S. mansoni affects the large bowel and the liver; presinusoidal poal hypeension, splenomegaly, and esophageal varices may be complications. Pulmonary hypeension, often fatal, may be seen with S. mansoni and S. japonicum disease. * Eggs may be found in an unstained specimen of rectal mucosa or in stool. Urine microscopy and liver biopsy, when warranted, often prove positive. Schistosomiasis is best prevented by the elimination of the parasite in snails before human infection occurs.