Most Common Site of CMV Enteritis
The colon is the most common site of involvement in CMV enteritis, with colonic localization being the predominant manifestation of gastrointestinal CMV infection in immunocompromised patients. 1
Anatomic Distribution Pattern
CMV colonic localization is explicitly stated as "the most common" site of gastrointestinal involvement, causing vasculitis that ultimately leads to bowel wall necrosis 1
The cecum and ileocecal valve region appear to be particularly affected, with some studies identifying typical cecum ulcers involving the ileocecal valve as a specific finding in CMV colitis, especially in patients with graft-versus-host disease 1
CMV enteritis may affect any region of the bowel, but the colon remains the predominant site 2
Small Bowel Involvement is Uncommon
The small bowel is explicitly described as "the least common site of involvement in the gastrointestinal tract for cytomegalovirus infection" 3
When small bowel CMV enteritis does occur, it results in a high rate of emergency surgery for bleeding, perforation, or ileus, and carries a high mortality rate 3
Small bowel involvement may be present in up to 40% of CMV infections as concurrent disease (often with duodenal or terminal ileal involvement), but isolated small bowel disease without colonic involvement is exceedingly rare 1, 4
Clinical Implications
The predominance of colonic involvement means that colonoscopy with multiple biopsies remains the cornerstone diagnostic approach, with biopsies targeting ulcer bases and edges where CMV-positive cells are most concentrated 5, 6, 7
Pancolic appearance is rare and may help differentiate CMV colitis from other conditions like Clostridioides difficile colitis 1
The presence of small bowel thickening on CT scan (present in up to 40% of CMV infections) is absent in C. difficile colitis and can aid in differential diagnosis 1