Parasitic organisms include cryptosporidium, isospora, entamoeba histolytica, giardia, and microsporidia. Viruses include CMV and adenovirus, fungi including histoplasmosis. Most treatable conditions can be diagnosed with straightforward stool studies. Although easy to diagnose on stool studies, one difficult to treat condition is cryptosporidium. Patients who are on aggressive retroviral regimens may recover enough of their immune system to clear cryptosporidium on their own.
Treatment is otherwise unsuccessful.
MAC is theoretically treatable but is seen late in the course of the disease at a time when multi-organ involvement and complications have set in, and treatment may not prolong life. Cytomegalovirus may be treated and the gross appearance of the colon may improve, but symptoms may not resolve despite apparent clearing of the infection. Symptoms of the diarrhea may also help diagnose the cause of the condition. Small bowel diarrhea usually presents with malabsorption, periumbilical pain, large volume diarrhea, dehydration but no WBC's nor tenesmus and is seen. Causative organisms presenting in this manner include cryptosporidium, microsporidium and giardia.