Isospora belli infection associated with acalculous cholecystitis in a patient with AIDS

The protozoan parasite Isospora belli may cause acalculous cholecystitis in patients with AIDS. Acalculous cholecystitis is an inflammation of the gallbladder without gallstones. Six years after diagnosis with AIDS, a 39-year-old man experienced abdominal pain, nausea, vomiting and diarrhea. His gallbladder was surgically removed and showed evidence of chronic cholecystitis. Pathologic examination of the gallbladder found no disease-causing organisms. The patient died following colon surgery four months after the gallbladder surgery. Two years later, however, the gallbladder was reexamined as part of a study of gallbladder disease in AIDS patients and Isospora belli parasites were identified. Isospora belli infection is treatable with the antibiotic trimethoprim-sulfamethoxazole. Although the infection is most commonly found in tropical or subtropical areas, it has been found in the US. Diagnosis of gallbladder disease in AIDS patients should include evaluation for Isospora belli infection.