Merck Manual

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Anoscopy and Sigmoidoscopy


Jonathan Gotfried

, MD, Lewis Katz School of Medicine at Temple University

Reviewed/Revised Mar 2023
Topic Resources

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 Contraindications to Gastrointestinal Endoscopy Flexible endoscopes equipped with video cameras can be used to view the upper gastrointestinal tract from pharynx to proximal duodenum and the lower gastrointestinal tract from anus to cecum... read more Contraindications to Gastrointestinal Endoscopy should be considered. Other relative contraindications include recent anal surgery, anal strictures, and suspected perirectal abscess.

How to do Anoscopy

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, and this instrument is less commonly used in current practice.

Sigmoidoscopy is done after giving an enema to empty the rectum. IV medications 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 past the anal sphincter and advanced into the rectum and sigmoid colon.

Anoscopy may be done without preparation. The anoscope is inserted to its full length, usually with the patient in the left lateral position. Complications of anoscopy are exceedingly rare when the procedure is done properly.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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