Hello everyone, 1.I was wondering what is the exact mechanism that rectal cancer gives a sense of incomplete evacuation after defecation (Tenesmus in scientific language). Also why is this is not present in colon cancer higher up eg in ascending colon cancer and only lower down like rectal cancer? 2. Also while we are at it. Why does alteration of bowel habits occur in rectal carcinoma? What I think is, due to the colon lumen obstruction by the cancer first you get constipation and faeces build up. The bacteria work on this faeces and break them in to liquid, causing diarrhoea. Am I right?