AIM:To detect the presence of human cytomegalovirus(HCMV)proteins and genes on the ileal pouch of patients with ulcerative colitis who have undergone proctocolectomy with ileal pouch-anal anastomosis(IPAA).METHODS:Immunohistochemistry,polymerase chain reaction(PCR)and PCR sequencing methods were utilized to test the presence of HCMV in pouch specimens taken from 34 patients in 86 endoscopies.RESULTS:HCMV genes and proteins were detected in samples from 12(35.2%)patients.The rate of detection was significant in the endoscopies from patients diagnosed with pouchitis(5 of 12,41.6%),according to the Japanese classification of pouchitis,in comparison to patients with normal pouch(7 of 62,11.2%;P = 0.021).In all patients with pouchitis in which the HCMV was detected,it was the first episode of pouchitis.The virus was not detected in previous biopsies taken in normal endoscopies of these patients.During the followup,HCMV was detected in one patient with recurrent pouchitis and in 3 patients whose pouchitis episodes improved but whose positive endoscopic findings persisted.CONCLUSION:HCMV can take part in the inflammatory process of the pouch in some patients with ulcerative colitis who have undergone proctocolectomy with IPAA.