I had lar for rectal cancer 5mo ago. now, i have a persistent groove line in my stool (same size as before surgery). normal cea. what's the cause?

More fiber in diet: You probably are seeing narrow stool when you say "groove" in your stool. The size and girth of the stool is a function of fiber in your diet. If it is because of a stricture at the anastomotic site (narrowing at the bowel hook-up) you would have more symptoms of difficulty with defecation or abdominal distension and pain. Eat more fruits, vegetables and add psyllium seeds (like metamucil).

Not sure: There is any significance to a groove, but you may discuss this with your surgeon. The procedure uses a circling stapling device to bring the resected ends together, occasionally this is done by hand. Control of your bowels, lack of blood all positive signs. Does not sound like cancer. Talk to the surgeon about your concern.