Colonic polyposis. Polyps lining the colon (large bowel or intestine). Such polyps or adenomas may be caused by a genetic disease called Familial Adenomatous Polyposis (FAP). Most polyps are benign and without symptoms, but they may cause bleeding and anaemia. Abdominal pain is rare. Polyps are looked for by colonoscopy. In the case of FAP, genetic screeing for the faulty gene can be carried out. The polyps usually become malignant (cancerous) later in life necessitating removal of all or part of the colon.