A 62 year-old-man with low anterior rectal resection and protective ileostomy, for low rectal neo and neoadjuvant QT +RT. Then ileostomy closure without incidences. On the 3rd postoperative day, he started with fever peaks and diarrhea. An abdominal CT scan showed diffuse thickening of the wall of the descending colon compatible with colitis and colonoscopy showed deep rectal ulcers with punch-like morphology with hyperemic mucosa with erythematous stippling of erosive appearance, showing this ulcerative pattern with numerous lesions and intensely edematous and congestive mucosa covered with abundant fibrinopurulent exudate in the descending colon. Biopsies and stool cultures were negative, but serologies were positive for CMV. Suspected CMV infection in a immunosuppressed by chemotherapy patient, he was treated with ganciclovir. The patient presented clinical improvement, without fever or diarrhea and improvement of the punch ulcers in the endoscopic controls, so he could be discharged from the hospital with follow-up in the outpatient consulting offices.