My Dad Had A Hemicolectomy A Few Months Back And

My Dad had a hemicolectomy a few months back and we are planning to get a scan done as a follow up - am guessing it's a CT scan. However, for the prep, the doctor has advised us to take 'pegmove' as well as 'rifagut'. One seems to be to prevent constipation and the other to treat diarrhea. This seems to be contradicting. Would you be able to tell if this is standard practice?