A 45-year-old man comes to the office due to a month of intermittent bloody diarrhea and abdominal pain and a 4-kg (9-lb) unintentional weight loss. The patient has no dizziness or chest pain. He was diagnosed with HIV a year ago after several years of intravenous heroin use. The patient does not take antiretroviral treatment consistently and no longer uses recreational drugs. He is currently engaged to an HIV-negative woman. The patient has never traveled abroad. Temperature is 38 C (100.4 F), blood pressure is 114/68 mm Hg, and pulse is 96/min. The mucous membranes are moist, and moderate cervical lymphadenopathy is present. Abdominal examination shows mild tenderness in the left lower quadrant. Laboratory results are normal except for a CD4 count of 28/mm³ and a potassium count of 3.2 mEq/L. What is the most likely cause of this patient's diarrhea?

Question

Quizplus · Accepted Answer

11ec25c8_d449_dd0d_bc81_df29a6404bbd_MD0003_00 Patients with advanced AIDS are at high risk for infectious diarrhea due to a variety of opportunistic bacterial, viral, and protozoal pathogens. Although delineation of the underlying organism typically requires stool and blood evaluation, a specific diagnosis is often suspected based on the quality (eg, watery or bloody, small or large volume) and frequency of the diarrhea. In this case, the presence of low-grade fever, abdominal pain, intermittent bloody stools, and a CD4 count <50/mm³ raises strong suspicion for cytomegalovirus (CMV) colitis. CMV is a common opportunistic pathogen in patients with untreated AIDS; it is most prone to attack the retina and gastrointestinal system. CMV colitis generally presents with progressive fatigue, low-grade fever, weight loss, and frequent, low-volume, bloody stools. As with other causes of diarrhea, hypokalemia may be present but is nonspecific. Diagnosis is typically made using colonoscopy with biopsy (eosinophilic intranuclear and basophilic intracytoplasmic inclusions). Although most patients with CMV colitis have evidence of CMV viremia, the presence of viremia cannot be used to diagnose end-organ disease (because viremia can occur without end-organ damage). Treatment with ganciclovir improves symptoms, but patients require antiretroviral therapy to prevent relapse. All patients with active CMV also require an ocular examination to rule out concurrent retinitis. (Choice A) Cryptosporidiosis is a common cause of chronic, profuse, watery diarrhea in patients with AIDS who have CD4 counts <180/mm³. This pathogen does not typically cause bloody stools. (Choice C) Entamoeba histolytica can cause bloody stools and fever but most often is acquired during international travel in countries with poor sanitation. It is not a common opportunistic pathogen in patients with AIDS in the United States. (Choice D) Giardia causes malabsorptive, watery diarrhea. It can become chronic and result in significant weight loss (10%-20% or more) in patients with AIDS. However, it does not typically cause bloody stools. (Choice E) Herpes simplex is usually associated with painful esophagitis or genital lesions in patients with HIV. It is an uncommon cause of colitis compared with CMV. (Choice F) Kaposi sarcoma (KS) of the gastrointestinal tract can cause hematochezia, but fevers would be less likely. AIDS-related KS is much more common among men who have sex with men than among other populations with HIV (eg, intravenous drug users). (Choice G) Disseminated Mycobacterium avium complex infection can cause chronic diarrhea and weight loss; however, the diarrhea is typically watery, not bloody. Educational objective: Patients with AIDS who have CD4 counts <50/mm³ are at high risk for infectious colitis with opportunistic bacterial, viral, and protozoal pathogens. Cytomegalovirus colitis should be suspected in those with frequent, small-volume, bloody stools and abdominal pain. Diagnosis is confirmed by colonoscopy with biopsy. Any patient with HIV who has active CMV disease requires ocular examination to rule out concurrent retinitis.

A 45-Year-Old Man Comes to the Office Due to a Month