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The colon is a common site of gastrointestinal disease in patients with AIDS, and the frequency and severity of disease increases as immunosuppression worsens. In these individuals, the most common manifestations of colonic disease include diarrhea, lower gastrointestinal bleeding, and abdominal pain. Gastroenterologists caring for HIV-infected patients with colonic disease must be aware of the causes of these diseases and the proper endoscopic techniques needed to make an accurate diagnosis. This article reviews the indications for lower endoscopy and the differential diagnosis of colonic disease in patients with AIDS. The authors also review the techniques of colonoscopy, sigmoidoscopy, ileal intubation, and biopsy. In addition, the authors discuss the endoscopic appearances of various colonic diseases in patients with AIDS to assist the endoscopist in correctly identifying these disorders. This is a US government work. There are no restrictions on its use.

We performed a randomly assigned, double-masked, placebo-controlled study in 78 patients with varied iris pigmentation to evaluate the influence of iris pigmentation on the ability of 0.1% thymoxamine to reverse mydriasis produced by 2.5% phenylephrine. Patients were chosen so that a 1.6:1 ratio of dark to light irides was obtained. Within one-half hour after medication, thymoxamine-treated nonbrown irides constricted significantly compared to their fellow placebo-treated irides (P < .001). Thymoxamine-treated pupils of nonbrown irides were 1.0 to 3.1 mm smaller than placebo-treated fellow eyes. Thymoxamine-treated light brown irides constricted less (0.6 to 2.0 mm) and more slowly compared to fellow placebo-treated irides. Thymoxamine did not reverse the mydriasis in eyes of patients with dark brown irides. Thymoxamine appears similar to other adrenergic agents that bind to melanin, delaying onset and strength of action. Its efficacy as presently formulated may be limited, in part, by iris color.