Cryptosporidiosis: rectum

Cryptosporidium parvum in the rectum This is a high power view of a rectal biopsy from a patient with HIV-2 infection. Several cryptosporidia are present (very small, round organisms in the lumen of the gland). They appear to lie on the surface of the epithelium, but they are in fact intracellular. H&E stain. The specimen was obtained by rectal biopsy. Biopsy is sometimes needed for the diagnosis of cryptosporidiosis, when parasitological examination is negative or affected organs are difficult to sample (eg. the biliary system).