Ipilimumab-associated colitis: CT findings.

The purpose of this article is to describe the CT findings of ipilimumab-associated colitis. In this retrospective study, 16 patients diagnosed with ipilimumab-associated colitis and available CT scans obtained at the time of symptoms were found by a search through the electronic medical record database. Two radiologists reviewed the CT images in consensus for the presence of bowel wall thickening, bowel mucosal enhancement, bowel distention, pneumatosis, pericolic fat stranding, and mesenteric vessel engorgement. Medical records were reviewed to note clinical features, management, and outcome. The common CT findings of ipilimumab-associated colitis were mesenteric vessel engorgement (13/16 [81.3%]) followed by bowel wall thickening (12/16 [75%]) and fluid-filled colonic distention (4/16 [25%]). None of the patients had pneumatosis or halo or target signs. Two distinct CT patterns of ipilimumab-associated colitis were observed: first, the diffuse colitis pattern (n = 12), which is characterized by mesenteric vessel engorgement with mild diffuse bowel wall thickening or fluid-filled distended colon; and, second, the segmental colitis associated with diverticulosis (SCAD) pattern (n = 4), which is characterized by segmental moderate wall thickening and associated pericolic fat stranding in a segment of preexisting diverticulosis. Clinical features and management also differed according to the CT pattern. Patients with the diffuse colitis pattern presented with watery diarrhea and were treated with steroids, whereas the patients with the SCAD pattern presented with mixed watery and bloody diarrhea and cramping pain and were treated with steroids and antibiotics. Two different radiologic and clinical manifestations of ipilimumab-associated colitis were observed: the diffuse colitis pattern and the SCAD pattern.