Background
Rigid sigmoidoscopy is usually performed in an outpatient or theater setting in conjunction with a digital rectal examination (DRE) to help facilitate the diagnosis and the management of rectal and anal pathology.
Rigid sigmoidoscopy may produce lesser diagnostic yield than flexible sigmoidoscopy does. In one study, 33.9% of the examinations declared normal by rigid sigmoidoscopy were found to include significant lesions when the examination was performed with flexible sigmoidoscopy. [1] Rigid sigmoidoscopy has been found to be a good tool for assessing patients with ulcerative colitis in remission, [2] and it can serve as an alternative to conventional flexible sigmoidoscopy or colonoscopy in this setting.
Indications
Indications for rigid sigmoidoscopy include the following:
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Presence of symptoms that suggest anorectal pathology, including colorectal neoplasia; however, some have questioned the diagnostic accuracy of rigid sigmoidoscopy for rectal cancer [3]
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Prior to anorectal procedures in the clinic or operating theater - A study by Chon et al reported using rigid sigmoidoscopy to manage anorectal stricture with the help of an insulated-tip knife [4]
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Biopsy of any bowel condition within the reach of the instrument
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Assessing the true height (distance from anal verge) of rectal cancers [5] - Magnetic resonance imaging (MRI) has been studied as an alternative to rigid sigmoidoscopy for this purpose [6] ; Han et al reported the use of two anal verge markers after rectal filling with gel, followed by MRI, to accurately measure the distance of the rectal cancer from the anal verge and found this newer method to have a good correlation with rigid sigmoidoscopy [7]
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Conservative treatment of sigmoid volvulus [8] - Rigid sigmoidoscopy has been safely employed as a bridge procedure to surgery for acute sigmoid volvulus [9]
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Gauging the lower resection margin during anterior resection of the rectum
Contraindications
Contraindications for rigid sigmoidoscopy can be divided into absolute and relative. Relative contraindications can be further divided into surgical and medical groups.
Absolute contraindications include the following:
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Suspected or known bowel perforation
Relative surgical contraindications include the following:
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Colonic necrosis
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Fulminant colitis
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Diverticular abscess
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Recent colonic surgery
Relative medical contraindications include the following:
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Severe coagulopathy
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Severe thrombocytopenia
Rigid sigmoidoscopy may also be contraindicated in patients who are highly uncooperative, agitated, or particularly anxious. [10, 13]
In some cases, sigmoidoscopy after colonic surgery may be necessary for evaluation of bleeding or obstruction. This procedure appears to be relatively safe in stable patients; however, it is best deferred until at least 1 week after the operation and reserved for clinically important indications. [12, 14, 15]
Technical Considerations
Anatomy
The rectum lies in the sacrococcygeal hollow and changes to the anal canal at the puborectal sling formed by the innermost fibers of the levator ani. The rectum has a dilated middle part called the ampulla. The rectum is related anteriorly to the urinary bladder, prostate, seminal vesicles, and urethra in males and to the uterus, cervix, and vagina in females. Anterior to the rectum is the rectovesical pouch in males and the rectouterine pouch in females.
The anal canal is related to the perineal body in front and the anococcygeal body behind; both of these are fibromuscular structures.
For more information about the relevant anatomy, see Large Intestine Anatomy, Colon Anatomy, and Anal Canal Anatomy.
Complication prevention
High-risk patients such as those with valvuloplasties need appropriate antibiotic prophylaxis. [10, 16] Sigmoidoscopy is safe in patients with even advanced HIV infection. [14]
If sigmoidoscopy following colonic surgery is judged necessary for evaluation of bleeding or obstruction, it should be postponed until at least 1 week after the operation. [12]
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Rigid sigmoidoscopy. Sims position.
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Rigid sigmoidoscopy technique. Video courtesy of Neil Fainges, Mater Health Services Multimedia team.
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Equipment needed for rigid sigmoidoscopy. Photo courtesy of Vicki Adams, Senior Medical Photographer, Mater Health Services Multimedia team.
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Assembled rigid sigmoidoscope. Photo courtesy of Vicki Adams, Senior Medical Photographer, Mater Health Services Multimedia team.
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Basic anatomy of rectum.
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Maneuvering through rectal valves.
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Equipment for performing rigid sigmoidoscopy.
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Assembly of rigid sigmoidoscope.
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Rigid sigmoidoscopy. Proper positioning and anatomy of patient.
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Digital rectal examination preceding sigmoidoscopy.
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Insertion of rigid sigmoidoscope and removal of stylet.
