My Father Has Multiple Colon Polyps Which Were Confirmed To

My father has multiple colon polyps which were confirmed to be benign. Recently he had a bout of acute gastritis. Tests revealed that lipase ,amylase along with crp levels were high. USG did not detect any abnormalities.Stool culture found occult blood, pus cells and vegetable cells in stool.His condition is stable now though the stool colour is dark green and he has mild anaemia ( haemoglobin level 11.4). I would be grateful if you can kindly give me any suggestion about what the next step should be and what are the possible implications of all these results?