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GASTROINTESTINAL TRACT PATHOLOGY IN AIDS

The gastrointestinal (GI) tract is the second most common organ system site for
opportunistic infections or neoplasms associated with AIDS. The GI tract and its abundant
lymphoid tissue serve as a reservoir for ongoing HIV proliferation. Chronic HIV infection of the
GI tract depletes protective CD4 cells and TH17 lymphocytes while increasing inflammatory
cytokines that disrupt the epithelial barrier from damage to cellular tight junctions as well as
translocation of luminal bacteria.[47]
The most frequent clinical symptom resulting from GI involvement is diarrhea, and the
etiologies for this symptom are numerous. Diarrhea may appear with acute HIV infection, but
typically it is manifested in patients with clinical AIDS.[487,662] In a few cases this diarrhea
may be severe and life-threatening. In patients receiving antiretroviral therapy (ART), the
frequency of gastrointestinal involvement with opportunistic infections is greatly
diminished.[663]
In general, pathogens that involve the small intestine produce signs and symptoms that
include large volume watery stools (up to 10 L/day), abdominal cramping, bloating, gas, and
weight loss with wasting syndrome. Malabsorption can lead to vitamin and other nutrient
deficiencies. Bacterial pathogens involving the colon most often produce frequent but small
volume stools with painful defecation. Fever is often present. The stools can be bloody or
mucoid with leukocytosis, typical for colitis. Stool culture provides a definitive diagnosis.
Septicemias in association with infections of the gastrointestinal tract are uncommon.[499]
In many cases, examination of stool for ova and parasites, stool culture, and tissues from
endoscopic biopsy procedures may reveal an etiologic agent for the diarrhea. Sometimes no
specific cause can be identified, and only chronic nonspecific inflammation with small intestinal
villous atrophy and crypt hyperplasia is seen on biopsy.[662]
A cost-effective strategy for clinical management of diarrhea employs initial use of stool
culture and direct microscopy of stool specimens, with additional diagnostic testing for non-
respondents to symptomatic treatment. Esophagogastroduodenoscopy (EGD), or colonoscopy
with biopsy, comprises the second phase of this evaluation. The use of EGD in cases where
esophageal symptoms are refractory to antifungal therapy, or when gastrointestinal bleeding is
present, is more likely to generate findings that influence subsequent patient management. EGD
is less useful for evaluation of abdominal pain, nausea, and vomiting. Small intestinal biopsies,
particularly those from the jejunum, are useful for histopathologic diagnosis, but small intestinal
aspirates are of little value.[487,664] The distribution of AIDS-diagnostic diseases in GI tract is
shown in Table 5. About 7% of deaths in AIDS patients result from diseases of the
gastrointestinal tract.[417]

FUNGAL INFECTIONS.-- Oral candidiasis in the form of thrush is a frequent finding in
patients with HIV infection that presages development of clinical AIDS or occurs in association
with AIDS.[473] The risk for development of oral thrush is increased with smoking.[216]
Persons who have a T-helper 2 (HT-2) type of cytokine response to HIV infection have an
increased susceptibility to mucosal candidiasis.[665]
Candida esophagitis is one of the most common GI tract manifestation of AIDS in both
adults and children, and patients with oral and esophageal candidiasis usually present with