Rigid Sigmoidoscopy

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 for rigid sigmoidoscopy include the following:

• Presence of symptoms that suggest anorectal pathology, including colorectal neoplasia; however, some have questioned the diagnostic accuracy of rigid sigmoidoscopy for rectal cancer ^[3]
• 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]
• Biopsy of any bowel condition within the reach of the instrument
• 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]
• Conservative treatment of  sigmoid volvulus ^[8]  - Rigid sigmoidoscopy has been safely employed as a bridge procedure to surgery for acute sigmoid volvulus ^[9]
• Gauging the lower resection margin during anterior resection of the rectum

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:

• Suspected or known bowel perforation
• Anal stenosis (technical consideration) ^{[10, 11]}

Relative surgical contraindications include the following:

• Acute peritonitis
• Colonic necrosis
• Fulminant colitis
• Toxic megacolon
• Acute severe diverticulitis
• Diverticular abscess
• Recent colonic surgery
• Anal fissure ^{[10, 11, 12]}

Relative medical contraindications include the following:

• Severe coagulopathy
• Severe thrombocytopenia
• Severe neutropenia ^[12]

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]

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]

The equipment required to perform rigid sigmoidoscopy includes the following items (see the image and video below):

• Scope
• Stylet (obturator)
• Eyepiece
• Bellows
• Light source
• Air filter
• Water-based lubricant
• Protective clothing as indicated (eg, gloves, apron, face mask, goggles)

Equipment needed for rigid sigmoidoscopy. Photo courtesy of Vicki Adams, Senior Medical Photographer, Mater Health Services Multimedia team.

Sherwinter reported on a novel introducer constructed from available operating room supplies that converts a standard laparoscope into a high-definition rigid sigmoidoscope.[17]

If a light source fails—an event that is not uncommon—a temporary solution is to remove the bulb and mains supply unit from the light source and insert a disposable pen torch in its place.[18]

A study by Lewis et al (N = 50) described the use of a novel digital rigid sigmoidoscope to assess rectal disorders.[19] This device was able to facilitate the clinical diagnosis in 96% of cases and was useful in outpatients irrespective of bowel preparation method. The technology provided good audiovisual output that could be recorded and employed in a "watch-and-wait" policy for some disorders. The authors found the digital rigid sigmpoidoscope to have significant potential for proctoring and training.

Anesthesia

Rigid sigmoidoscopy is most often performed without sedation.

Positioning

The left lateral (Sims) position, in which the patient lies on his or her left side with the hips and knees flexed and parallel (see the image below), is probably the position most commonly used for rigid sigmoidoscopy.

Rigid sigmoidoscopy. Sims position.

In this position, the buttocks must overhang the edge of the bed, with the patient’s trunk angled obliquely across the bed, to permit the full maneuverability of the scope (see the video below); the more transverse across the bed, the easier the examination. A small sandbag may be placed under the left thigh or hip to provide elevation. This ensures that the head of the sigmoidoscope can be depressed below the level of the bed.[10, 11, 12, 20, 21]

An alternate position is the prone knee-elbow or jackknife position, in which the patient lays prone in an inverted position on a specialized table. These positions are particularly helpful for allowing the scope a considerable degree of maneuverability. When this position is desired but only a normal examination bed is available, a cooperative patient can still be placed in the knee-chest position.[10, 11, 12, 20, 21]

With the patient in position, assemble the rigid sigmoidoscope (see the video and image below). Check that the light source is functioning by connecting it to a power source. Connect the bellows’ tubing to an intercepting disposable air filter. Remove the stylet from the scope. Connect the light source, bellows–air filter, and scope to the eyepiece. Open the eyepiece window and insert the stylet through the eyepiece into the scope, ensuring that the tip of the stylet protrudes through the tip of the scope. Apply generous amounts of a water-based lubricant to the scope.

Assembled rigid sigmoidoscope. Photo courtesy of Vicki Adams, Senior Medical Photographer, Mater Health Services Multimedia team.

Inspect the anus and surrounding areas for any abnormalities. Next, perform a digital rectal examination (DRE; see the video below). A DRE must always be done before rigid sigmoidoscopy. Make special note of the general anatomy of the distal rectum, any palpable lesions, and the contents of the rectum. If the rectum is found to be loaded with feces, an attempt should be made to empty the rectum with the aid of a laxative suppository or enema before performing rigid sigmoidoscopy.

Hold the scope with the thumb, pushing on the base of the stylet to hold it in place (see the video below). Insert the scope 4 cm into the anus in the direction of the patient’s umbilicus. At this point, remove the stylet, and seal the eyepiece with the glass window.

Once the stylet is removed, advance the scope under direct vision, using the bellows to gently insufflate air into the rectum intermittently as the scope advances. Knowledge of the three-dimensional anatomy of the rectum is important.

At 4 cm from the anus, the rectum angulates posteriorly over the puborectalis sling into the hollow of the sacrum (see the image below).

Basic anatomy of rectum.

Therefore, when the scope reaches this point 4 cm from the anus, its general direction should change from pointing anteriorly to pointing posteriorly (see the video below).

Gently insufflate air into the rectum to expand the rectum in front of the scope. Under direct vision, advance the scope into the middle of the expanded segment. Repeat the insufflate-advance steps as the scope moves along. Note any abnormalities. A slight lateral angulation of the scope is used to maneuver through the rectal valves (see the image below).

Maneuvering through rectal valves.

At the 12 cm level, the sacral promontory produces a sharp angulation of the rectum anteriorly. At this point, the direction of the scope is changed to point anterosuperiorly.

The usual distance that can be examined comfortably is 15-20 cm. Any significant pain is an indication to terminate the examination. Further examination may be performed using a flexible scope.

As the scope is withdrawn, follow the above steps backward. Insufflate air and change directions while maintaining direct vision of the lumen of the rectum. Small circular motions allow a more complete examination and may reveal lesions missed during insertion of the scope.

Upon complete removal of the scope, wipe off the perianal area and return the patient to a more comfortable position.

Concerns have sometimes been expressed that because rigid sigmoidoscopy involves insufflation of air into the rectum, with the sigmoidoscopist's face 5-20 cm from the patient's anus, the air escaping from the anus may contaminate the examiner's face with fecal flora; however, a small study by Skittrall et al found there to be no clinically significant contamination in this scenario.[22]

Rigid sigmoidoscopy performed by trained clinicians is tolerated by most patients and has a low incidence of serious complications. However, some adverse effects and complications do occur.

Among patients who undergo rigid sigmoidoscopy, 60% report adverse effects. Most of these reported adverse effects are of low magnitude.[23] As many as 30% of patients experience moderate-to-severe discomfort during rigid sigmoidoscopy.[24] The following types of discomfort are commonly reported:

• Pain (33%)
• Discomfort from rectal preparation (13%)
• Uncomfortable desire to defecate (8%)
• Discomfort associated with patient positioning (4%) ^[23]

Negotiating the rectosigmoid angle as the rigid sigmoidoscope is inserted to a depth of 20 cm is the most likely cause of major patient discomfort, though insufflations of the rectum may also contribute to discomfort.[1]

Significant bleeding that necessitates transfusion or further procedural intervention occurs in approximately 1 out of 9400 rigid sigmoidoscopies.[25] This complication is usually related to concomitant rectal biopsy.[25]

Bacteremia occurs in 5% of patients during rigid sigmoidoscopy, which justifies the precaution for its use in patients with neutropenia.[26]