Fat malabsorption common cause of diarrhoea in HIV-positive patients

Fat malabsorption is a commonly undiagnosed cause of diarrhoea in HIV-positive patients, whether or not they have received highly active antiretroviral therapy (HAART), according to a report published in the June issue of the American Journal of Gastroenterology.

Dr. Michael A. Poles and colleagues from the University of California at Los Angeles assessed the incidence of fat malabsorption in 33 HIV-positive patients who underwent evaluation for diarrhoea between June 1995 and April 1999. Twelve of the patients were receiving HAART and 21 were receiving nucleoside analogues only.

All but three subjects had fat malabsorption, including 10 patients in the HAART group and 20 patients in the non-HAART group, the authors report. Mean stool fat weight was lower in the non-HAART group, but both groups had similar mean stool weights.

“The assumption has been that because HAART reduces the incidence of opportunistic infections there would be a subsequent decrease in diarrhoea,” Dr. Poles told Reuters Health. “Unfortunately that doesn’t seem to be the case, [because] HAART-treated patients still experience a significant rate of diarrhoea,” he said. “Fat malabsorption is probably a significant cause of diarrhoea in these patients, certainly worthy of an attempt at diagnosis and treatment.”

Dr. Poles noted that “in general, when we think of a cause for fat malabsorption we usually think of pancreatic disease.” However, “the patients in the current study did not seem to have any real evidence of pancreatic disease,” he said.

“The cause may be more at the molecular level,” Dr. Poles postulated. “Nucleoside analogues, and, to a lesser extent, protease inhibitors may have some effect on the pancreas. Findings from a post-mortem study of HIV-positive patients showed that a fairly large proportion do have some evidence of subclinical disease.”

Dr. Poles believes that physicians who see HIV-positive patients with diarrhoea need to first consider fat malabsorption in the differential diagnosis. “At our institution, we do a 24-hour faecal fat assay after a fat challenge,” he said. “Once we’ve found fat malabsorption, we treat the patient with pancreatic enzyme replacement.”