Hello. Blood in the stool is a significant symptom which can be caused by benign or less benign disorders. I have en experience that many patients who notice blood in the stool think of the worst scenario but there is no reason for it. Why? The most common disorders that cause such symptoms are benign. These are: Colonic angiodysplasia, polyps, fissures and hemoroids, inflamatory bowel disease, colitis etc. You sad u ve ruled out some of them,but still there is no reason to panic. Colon cancer is one of 3 most common malignant diseases, especially at male and age 55. Symptoms are depending on the site of tumor, proximal (closer to the small intestines) tumors are more difficult to diagnose and usually the first and the only sign is microcytic anaemia, opstipation is a late symptom. Distal tumors are closer to the anal canal and 50% of all tumors are localized in rectosigmoid colon which can be vizualized by sigmoidoscopy. Bright red blood in the stool is a sign of colonic lesion close to the anal canal, and darker blood(or black blood) is a sign of upper gastrintestinal bleeding(from stomach and small intestines). So u should also rule out these kind of bleeding by doing gastroscopy(do you have peptic ulcer?) ! GGT is a liver specific enzyme, usually raised in alacholic liver disease but levels u ve mentioned are not so high. The only reason why these enzymes are raised associated with colon pathology are liver matastasis,but it would be seen on CT scan. Ultrasound is useless in diagnosing colon pathology. So what sholud you do? 1. Colon tumor markers( CEA and CA19-9), you should really do this 2. Colonoscopy of course and gastroscopy 3. LAboratory findings: red blood count! to rule out anemia and need for transfusion