Hi and thanks for posting your query.. Welcome to HCM.. I am here to solve your query I read your question completely and have understood it well.. I being a surgeon, can tell you that there is definitely something to think about.. I am not trying to scare you or depress you. But, these things make me worry. 1. The classical description that you are giving, the history of alternative diarrhea and constipation. This Is classical of left sided colonic malignancy. 2. Age more than 50,is a definite risk factor and most importantly 3. A history with 5mm sigmoid polyp. These polys can turn into malignancy. But, do not worry. I am giving you the worst situations possible. Now how do we go about? These are the suggestions.. 1. Get him for Colonoscopy. This is the single and the best investigation. Better than barium in diagnosing cancer. It will straight away rule out malignancy after taking biopsy from suspicious areas. This biopsy thing is not possible in barium studies. And we shall pray and hope that, everything turns out to be normal. I being a doctor have to give you clear picture of the problem, instead of keeping you in the dark and giving false assurances. If Colonoscopy is not possible, He can get a fecal occult blood testing done. Although results are not satisfactory. Hope I have done my job, in case you need any further assistance. Contact me. Take care, God bless and I pray that nothing harmful should happen to you or dad.