AIM To describe all abnormal histological findings and their associated endoscopic presentation in patients using mycophenolate mofetil(MMF).METHODS A retrospective review of all individuals prescribed MMF within 6 mo of a colonoscopy or flexible sigmoidoscopy between 07/2009 and 09/2015 was performed within Northwell Health system.Records were analyzed for age,gender,procedure indication,MMF indication,and both gross and microscopic findings.Only reports with abnormal histology were included.RESULTS One hundred and eighty-four procedures from 170 patients were found,of which 39 met inclusion criteria.Fifty-one point three percent were female.MMF was used for solid organ transplant in 71.8%.Diarrhea was the indication for 71.8% of colonoscopies.Fiftynine percent of reports revealed gross and microscopic abnormalities while 41.0% had only microscopic findings.Only 11 patients’ reports(28.2%) indicated a specific histopathology of MMF colitis.Among the entire group,only 23.1% of abnormal histology was isolated proximal to the splenic flexure.CONCLUSION Our results demonstrate a high rate of left sided disease and microscopic findings without gross mucosal abnormalities among patients using MMF.Also,a broader definition of MMF-colonopathy may be appropriate,with a majority of our abnormal histology falling outside of the more narrowly defined MMF-colitis category.Given the high frequency of isolated microscopic abnormalities and distal disease,sigmoidoscopy with random biopsies may be an appropriate,less invasive initial endoscopic examination in selected MMF patients. AIM To describe all abnormal histological findings and their associated endoscopic presentation in patients using mycophenolate mofetil (MMF). METHODS A retrospective review of all the subjects prescribed MMF within 6 mo of a colonoscopy or flexible sigmoidoscopy between 07/2009 and 09/2015 was performed within Northwell Health system. Records were for age, gender, procedure indication, MMF indication, and both both gross and microscopic findings. All reports with abnormal histology were included .RESULTS One hundred and eighty-four procedures from 170 patients were found, of which 39 met inclusion criteria. Ftyty-one point three percent were female. MMF was used for solid organ transplant in 71.8%. Diarrhea was the indication for 71.8% of colonoscopies. Fiftynine percent of reports revealed gross and microscopic abnormalities while 41.0% had only microscopic findings .Only 11 patients’ reports (28.2%) indicated a specific histopathology of MMF colitis. Amm the entire group, only 23.1% of abnormal histology was isolated proximal to the splenic flexure. CONCLUSION Our results demonstrate a high rate of left sided disease and microscopic findings without gross mucosal abnormalities among patients using MMF. Also, a broader definition of MMF-colonopathy may be appropriate, with a majority of our abnormal histology falling outside of the more narrowly defined MMF-colitis category. Giving the high frequency of isolated microscopic abnormalities and distal disease, sigmoidoscopy with random biopsies may be appropriate, less invasive initial endoscopic examination in selected MMF patients.