A 44-year-old man has experienced intermittent low-volume diarrhea for the past month. He has noted no blood in the stool. During this time he has been feeling poorly and has lost 4 kg. Vital signs show T 38.9 C, P 80, R 14, and BP 100/65 mm Hg. The physical examination finds generalized non-tender lymphadenopathy. He has some tan to yellowish plaque-like areas on the lateral aspects of the tongue. The chest and abdominal examinations are normal. Active bowel sounds are present and there are no masses palpable and no abdominal tenderness. The rectal examination reveals external hemorrhoids. The stool is negative for occult blood.

A colonoscopy is performed, and the only finding is an area of mildly erythematous mucosa involving the cecum. Biopsies are taken.

Question 13.1: What is the most likely causative agent?

The large cells with the intranuclear inclusions and surrounding halo artifact are characteristic for cytomegalovirus. CMV colitis often produces minimal grossly apparent findings. Some cases may have hematochezia.

Question 13.2: What additional historical or laboratory findings are most likely to be present in this patient?

CMV is an infection of immunocompromised patients. The findings in the oral cavity suggest thrush, which is a finding also seen in immunocompromised patients. Further history reveals that he has had sex with other males.

Laboratory testing for HIV is indicated. He is positive, and his CD4 count is 190/microliter, which is consistent with a diagnosis of AIDS.

Question 13.3: How is this infection usually diagnosed?

Though CMV can be cultured, this is expensive and not typically performed in non-respiratory infections. Since his findings are gastrointestinal, and colonoscopy is performed, then biopsies will show the organisms. In immunocompromised patients, other infectious causes for diarrhea must also be considered. Stool cultures will routinely be done, and a stool for O & P as well.

Question 13.4 How is this infection treated?

CMV infection can be treated with ganciclovir. Another possible agent to use is foscarnet.

Question 13.5 What are possible complications?

CMV can be disseminated to other organs, with lung, adrenal, and brain the most likely targets. CMV can involve any part of the GI tract, but the esophagus and the colon are the most likely sites, or at least the ones which produce the most obvious signs and symptoms. There is the potential for ulceration and even perforation with CMV infection, but this is rare.