colonoscopy colon colonic rectal rectum anus anal anorectal anoscopy high resolution dysplasia AIN neoplasia cancer hemorrhoids hemorrhoidal THD hemorrhoidectomy fissure fistula abscess condyloma condylomata warts HPV human papilloma virus rubber banding ligation diverticular disease diverticulosis diverticulitis endoscopy colostomy ileostomy stoma ostomy fecal incontinence ulcerative colitis Crohn Crohn's disease ileitis pilonidal cyst sinus constipation diarrhea prolapse inflammatory bowel disease screening diagnostic therapeutic abdominal incisional hernia paracolostomy paraileosotmy