Flexible sigmoidoscopy is a commonly performed technique for examination of the rectum and distal colon. Sigmoidoscopy has been advocated for individuals older than 50 years of age every 3 to 5 years as a screening strategy to detect adenomas and colon cancer. The technique is safe, easily performed in an office setting, and produces a 30% to 40% reduction in colon cancer mortality. Training in endoscopic maneuvering and in anatomy and pathology recognition is required for performance of sigmoidoscopy. Experienced practitioners often perform the procedure in less than 10 minutes. Most physicians report comfort with performing the procedure unsupervised after completing 10 to 25 preceptor-guided sessions.
About 60% of all colorectal cancers are within reach of the sigmoidoscope. Rectal bleeding in individuals older than 50 years should be evaluated by full colonoscopy because of the risk for isolated proximal neoplasms beyond the view of the sigmoidoscope. Multiple options exist when evaluating a younger individual with rectal bleeding. For persons between the ages of 30 and 39 years, the incidence of colon cancer is only 3 cases per 1000 people, but differentiating the few with serious pathology from those with anal disease can be difficult. Because proximal lesions also peak in individuals before the age of 40 years, full colonoscopy and flexible sigmoidoscopy with barium enema are appropriate strategies for individuals between the ages of 30 and 49 years. Most bleeding in individuals younger than 30 years is caused by benign anal disease. Flexible sigmoidoscopy is a reasonable option in that age group if anoscopic findings are normal.
About 7% to 10% of flexible sigmoidoscopies reveal the presence of adenomas. Historically, the presence of an adenoma necessitated referral for colonoscopy to look for proximal neoplasia. Some physicians have recommended colonoscopy only for larger (>1 cm) adenomas, because larger lesions were more likely to have higher-risk villous features. However, the major benefit of universal biopsy of polyps discovered at sigmoidoscopy may be to distinguish tubular adenomas from villous adenomas. Persons with tubular adenomas of any size appear to have the same rate of proximal neoplasia as individuals with no adenomas at sigmoidoscopy (about 5.5%). A distal tubulovillous or villous adenoma has a higher rate of proximal neoplasia (about 12%), and this finding should incur referral for colonoscopy.
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Diminutive (<5 mm) polyps found at sigmoidoscopy often are hyperplastic. Although hyperplastic polyps generally are not thought to be associated with proximal adenomas, this opinion is not universally accepted in the literature. Many practices offer barium enema, and others recommend no further screening when hyperplastic polyps are found on sigmoidoscopic biopsy.
Many physicians recommend full colonoscopy for colon cancer screening every 10 years for all individuals older than 50 years. Individuals at higher risk (i.e., those with a family history of colon cancer) may benefit from this strategy. Significant feasibility issues continue to prevent this approach from being recommended for population screening. A more feasible strategy is to perform screening sigmoidoscopy at age 50 for average-risk individuals. Only a small proportion of screened individuals with an occult proximal neoplasm will have the lesion progress to symptomatic colon cancer, and those that do progress take many years. Periodic sigmoidoscopy followed by a single screening colonoscopy at age 65 may be a more appropriate, cost-effective population strategy.
The average procedure time for sigmoidoscopy without biopsy is about 17 minutes. Performance of a biopsy adds about 10 minutes to the procedure. Although it is desirable to insert the entire scope length (60 to 70 cm), the average depth of insertion is about 52 cm. Both procedure time and the depth of insertion appear to be operator dependent. Women have a more acute angle at the rectosigmoid junction, making endoscope passage more difficult. Studies in women also demonstrate that a history of prior pelvic or abdominal surgery increases the discomfort and decreases the depth of endoscope insertion. Sigmoidoscopy in women averages insertion depths of only 40 cm.
In a large series in England, about 80% of individuals rated the discomfort of sigmoidoscopy as “no or mild pain.” The remainder rated their discomfort as moderate to severe, with women reporting significantly more discomfort. About 16% stated their discomfort was greater than what they expected. Most procedures can be performed without sedation or analgesia, but if patients insist, premedication options include oral diazepam (10 mg) or triazolam (0.5 mg) taken 1 hour before the procedure, intranasal butorphanol (two squirts) immediately before the procedure, or intramuscular ketorolac (60 mg) administered 30 minutes before the procedure. Appendix F provides the guidelines for monitoring patients receiving conscious sedation for endoscopy procedures.
Adequate preparation of the left colon is essential for flexible sigmoidoscopy. Eating after midnight is highly associated with stool in the sigmoid, and patients must be instructed to consume only clear liquids the morning of the procedure. Most practices recommend the administration of one or two enemas before the procedure. Home administration of the enemas may reduce patient embarrassment and time demands on office nursing staffs. However, many patients refuse to administer home enemas, feeling unable to perform the task or fearing a mess. Proper education of enema administration and offering an alternate, orally administered bowel preparation may reduce noncompliance with home bowel cleansing. Appendix E provides recommendations for endoscope disinfection.
Individuals often choose not to undergo sigmoidoscopy. Offering fecal occult blood testing simultaneously with sigmoidoscopy can cause some patients to avoid the invasive procedure. Increased acceptance of sigmoidoscopy can be achieved by sending a letter describing the significance of colon cancer and inviting individuals to participate in colon screening. Other factors that may favorably increase the uptake of the procedure include enthusiasm of the primary care physician and staff for the procedure, telephone reminders before the procedure,
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higher levels of general education in the target population, and skill of the practitioner performing endoscopy (especially for repeated screening).
About one half of primary care physicians who are trained to perform flexible sigmoidoscopy do not continue the procedure in practice. One study documented that the main deterrents to continuing to offer the service included the time required to perform the procedure, the availability of the procedure from other physicians in their locale, and the availability of adequately trained staff. Low reimbursement for the time involved in the procedure, especially from the Medicare program, is often cited as a reason for discontinuing sigmoidoscopy screening.
INDICATIONS
RELATIVE CONTRAINDICATIONS
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PROCEDURE
This is the view from above the examination table of the proper positioning of the patient for the procedure. The patient is in the Sims or left lateral decubitus position, with the left side of the body down on the table. The left hip and knee are both flexed, and the right leg remains fairly straight.
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(1) View from above the examination table of the proper positioning of the patient for the procedure. |
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A rectal examination is performed with the lubricated, gloved index finger. The nondominant hand lifts the right buttock. The anal canal and distal rectum are examined for pathology and to exclude any obstruction, foreign body, or stool that may prevent endoscope insertion. Use of 5% lidocaine ointment may decrease discomfort from the subsequent endoscopic procedure.
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(2) Perform a rectal examination. |
PITFALL: Overly aggressive performance of a digital examination will make the patient uncomfortable and possibly reduce patient tolerance of the ensuing endoscopy. Perform the examination gently, and talk to the patient (i.e., verbal anesthesia) from the very beginning.
Because the endoscope does not visualize the anal canal well, many authorities recommend performance of anoscopy before sigmoidoscopy. The Ives anoscope is a slotted, metal scope that affords extensive viewing in the canal. The lubricated anoscope is inserted three times to view all three hemorrhoidal pads (see Chapter 52).
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(3) Because the endoscope does not visualize the anal canal well, performing an anoscopy before sigmoidoscopy is recommended. |
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The endoscope is held in the left hand. The umbilical cord to the light source sits over the thumb web space and travels across the wrist. The endoscope head sits in the palm of the hand. The left thumb operates the inner (up and down) and outer (right and left) control knobs. The index finger and middle finger depress the air or water and suction valves. The left fourth and fifth fingers grasp and support the endoscope.
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(4) The endoscope is held in the left hand. |
PITFALL: Many individuals with small hands complain about the difficulty of holding the endoscope. It may be difficult for the thumb to reach the outer knob if the operator's hand is small. Individuals with small hands must learn to turn the scope right and left by turning the scope using the right hand.
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The right hand is used to grasp the scope and to twist the scope (Figure 5A). This helps with the insertion techniques described later. As the left thumb moves the scope tip up and down (Figure 5B), the right hand can torque the curled scope tip to move it right or left (Figure 5C). Alternately, some practitioners prefer to have a nurse assistant perform the scope insertion and withdrawal and to use the right hand to work the outer (right or left) knob. Insertion by a second person limits the ability to feel tension on the colon wall and to perform torquing maneuvers.
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(5) The right hand is used to grasp and twist the scope. |
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The scope is lubricated with water-soluble jelly, and insertion is performed by direct insertion of the scope tip into the anus or by pushing the scope tip inside with the index finger behind the scope. Some practitioners press tangentially on the anal verge to facilitate insertion.
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(6) Lubricate the scope with water-soluble jelly, and directly insert the scope tip into the anus. |
PITFALL: Do not apply lubricating jelly on the tip of the scope because it will smear the lens and distort the image.
PITFALL: Care must be taken when inserting the scope in women to avoid an embarrassing and potentially injurious intravaginal insertion.
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The scope is inserted into the rectum (7 to 17 cm), and air is insufflated to reveal the lumen. Some practitioners suction fluid from the rectum. The lumen is used as a guide for insertion, thereby reducing patient discomfort and risk of perforation. Air can be continuously or intermittently inserted to open the inside of the colon for passage and viewing.
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(7) The scope is inserted into the rectum (7 to 17 cm), and air is insufflated to reveal the lumen. |
PITFALL: Avoid suctioning any solid stool, because this can rapidly dry and clog the suction channel, necessitating costly repairs to the endoscope. Even fluid in the rectum may have stool, and suctioning should be performed only when needed.
Insert the scope as rapidly as possible to limit patient discomfort and spasm, which can make insertion more difficult. Three transverse folds of mucosa are seen in the rectum (Figure 8A), and these are passed to enter the rectosigmoid. Torquing the endoscope with the right hand allows passage through turns (Figure 8B). Dithering is the rapid back-and-forth motion that sometimes facilitates finding the lumen and passing the scope.
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(8) Insert the scope as rapidly as possible to limit patient discomfort and spasm, which makes insertion more difficult. |
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The hooking and straightening technique may be used for passage through a tortuous sigmoid. As the endoscope is inserted in the sigmoid, the sigmoid may bow upward, producing significant patient discomfort (Figure 9A). The endoscope tip is maximally deflected (Figure 9B), and the sigmoid is “hooked” as the scope is withdrawn (Figure 9C). The scope tip can paradoxically appear to move forward through the lumen as the endoscope is withdrawn. The sigmoid is straightened (Figure 9D), and the endoscope passes through the sigmoid.
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(9) The hooking and straightening technique may be used for passage through a tortuous sigmoid. |
The endoscope is maximally inserted. Viewing takes place as the endoscope is withdrawn. Depicted are a diverticular opening, normal vascularity of the colon wall, a pedunculated polyp, and a cancer occupying one third of the wall of the colon. Use the markings on the endoscope to document depth of insertion of the scope for all pathology encountered.
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(10) The endoscope is maximally inserted. |
PITFALL: Do not mistake the lumen for a large diverticular orifice. The posterior walls of diverticular sacs can be quite thin, and perforation is easily accomplished by inadvertent entry into a diverticular sac.
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Biopsy is performed by threading the metal biopsy instrument through the biopsy channel. The open biopsy forceps can serve as a guide to the size of lesions, measuring approximately 5 mm when opened (Figure 11A). A syringe-like plunger on the end of the biopsy forceps is used to open and close the forceps (Figure 11B).
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(11) Biopsy is performed by threading the metal biopsy instrument through the biopsy channel. |
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After the endoscope is withdrawn to the rectum (i.e., 10 to 15 cm inserted), the scope tip is retroverted to examine the distal rectal vault. This area is not well visualized by the forward-directed scope as it passes the area. Retroversion is achieved by maximally deflecting the inner (up and down) knob with the left thumb while simultaneously inserting the scope with the right hand (Figure 12A). The black scope can be seen entering the rectum past some internal hemorrhoids and a hidden tumor (Figure 12B).
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(12) After the endoscope is withdrawn to the rectum (10 to 15 cm inserted), the scope tip is retroverted to examine the distal rectal vault. |
The scope is straightened, and the lumen viewed. Air is withdrawn from the rectum before the scope is withdrawn. The scope is immediately placed in soapy water, and the suction channel is flushed to prevent clogging of the channel. The anus is wiped clean with gauze, and the patient is offered the opportunity to go to the bathroom. The patient is permitted to get dressed after the procedure and before the findings are discussed.
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(13) The rectum is emptied of air before the scope is withdrawn. The anus is wiped clean wih gauze. |
PITFALL: Vasovagal responses are possible during or after the procedure. Patients should be allowed to sit for a minute with the legs dangling off the table before being allowed to get off the examination table.
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CODING INFORMATION
For coding purposes, sigmoidoscopy involves examination of the entire rectum, sigmoid colon, and may include a portion of the descending colon.
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INSTRUMENT AND MATERIALS ORDERING
Information on endoscopy equipment ordering, training, and atlases is provided in Chapter 49. The information on ordering the Ives anoscope is included in Chapter 52. Recommendations for endoscope cleaning appear in Appendix E.
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