Evaluation of Diarrhea in HIV positive patients:
1) History: exclude medications (particularly HAART and primarily protease inhibitors), lactose or food/fatty food intolerance, inadvertent use of cathartics (such as high dose vitamin C or sorbitol containing foods), or symptoms suggestive of a systemic infection or neoplasm (fever, weight loss for example). Then try to localize the segment of luminal GI tract most involved:
- cramps, bloating, and nausea suggest gastric or small-bowel involvement, or both, raising the possibility of infection with Cryptosporidium, Microsporidium, Isospora belli, Giardia, or MAC organisms
- hematochezia and tenesmus imply large-bowel inflammation resulting from CMV, Shigella, Campylobacter, Clostridium difficile, HSV, salmonella, or Yersinia infections
Note: the character, frequency, color, and odor of the stool are nonspecific in HIV-related GI syndromes.
2) Physical examination provides a few diagnostic clues in the evaluation of HIV-related diarrhea.
- Weight will assist in determining nutritional status
- Orthostatics can assist with degree of volume depletion, suggesting small bowel involvement
- Skin and mucous membranes may reflect underlying micronutrient deficiencies, associated with small bowel process
- Fever may indicate the possibility of opportunistic infections such as CMV, MAC
- Hepatosplenomegaly may suggest a systemic infiltrative process, such as MAC, histoplasmosis, or lymphoma
- Perirectal tenderness may suggest anorectal infection from gonorrhea or Chlamydia or lymphogranuloma venereum
- Guaiac positive stools in a patient with advanced immunosuppression may suggest mucosal disease such as CMV or HSV proctitis
3) Laboratory: stool culture for enteric bacteria, Clostridium difficile toxin (in the setting of antibiotic use), and at least THREE stool specimens for O&P (including AFB and trichrome stain).
4) Consider sigmoidoscopy to help identify CMV infection if stool studies are negative. Consider colonoscopy for diagnosis of isolated right colonic CMV. Also upper endoscopy with biopsy of the terminal ileum can uncover small-bowel infection by Cryptosporidium, Microsporidium, or M. avium. Duodenal fluid can also be aspirated to assess for protozoal infection or small-bowel overgrowth.
Radiographic contrast studies generally are not useful in evaluating diarrhea in these patients since most disorders require mucosal biopsy. CT scan may show evidence of colitis (CMV, HSV, Clostridium difficile), abdominal adenopathy or hepatosplenomegaly (MAC, tuberculosis, histoplasmosis, lymphoma) or biliary tract disease.