(See also How To Do Anoscopy.)
Anoscopy and sigmoidoscopy are used to evaluate symptoms referable to the rectum or anus (eg, bright rectal bleeding, discharge, protrusions, pain). In addition, sigmoidoscopy also allows for biopsy of colonic tissues and application of intervention such as hemostasis or intraluminal stenting. There are no absolute contraindications, except contraindications for regular endoscopies should be considered. Patients with cardiac arrhythmias or recent myocardial ischemia should have the procedure postponed until the comorbid conditions improve; otherwise, patients will need cardiac monitoring. Other relative contraindications include recent anal surgery, anal strictures, and suspected perirectal abscess.
The perianal area and distal rectum can be examined with a 7-cm (typically 19-mm diameter) anoscope, and the rectum and sigmoid can be examined with a rigid 25-cm or a flexible 60-cm instrument. Flexible sigmoidoscopy is much more comfortable for the patient and readily permits photography and biopsy of tissue. Considerable skill is required to pass a rigid sigmoidoscope beyond the rectosigmoid junction (15 cm) without causing discomfort.
Sigmoidoscopy is done after giving an enema to empty the rectum. IV drugs for sedation are usually not needed unless the patient has severe anal pain. The patient is placed in the left lateral position. After external inspection and digital rectal examination, the lubricated instrument is gently inserted 3 to 4 cm past the anal sphincter. At this point, the obturator of the rigid sigmoidoscope is removed, and the instrument is inserted further under direct vision.
Anoscopy may be done without preparation. The anoscope is inserted its full length as described above for rigid sigmoidoscopy, usually with the patient in the left lateral position. Complications of anoscopy are exceedingly rare when the procedure is done properly.