Key points

Videos of removal of a colon polyp during retroflexion in the right colon and retroview of a polyp accompany this article at http://www.gastro.theclinics.com/

Introduction

Most endoscopists perform retroview during colonoscopy. Most often, this is a retroflexion in the rectum to observe the rectal ampulla and to view the areas near the anus directly and up close. This maneuver is accomplished by performing a turn-around or U-turn maneuver in the capacious rectal ampulla, but retroflexion can also be performed in the proximal colon in a similar fashion. Because of the narrowing and multiple twists in the sigmoid colon, it is often difficult to perform retroflexion with a colonoscope in the left colon or sigmoid colon.

Introduction

Most endoscopists perform retroview during colonoscopy. Most often, this is a retroflexion in the rectum to observe the rectal ampulla and to view the areas near the anus directly and up close. This maneuver is accomplished by performing a turn-around or U-turn maneuver in the capacious rectal ampulla, but retroflexion can also be performed in the proximal colon in a similar fashion. Because of the narrowing and multiple twists in the sigmoid colon, it is often difficult to perform retroflexion with a colonoscope in the left colon or sigmoid colon.

Rectal retroflexion

When colonoscopy was introduced as an alternative to the barium enema, rectal retroflexion was often performed inadvertently as the deflected tip turned around as the shaft was pushed forward. It did not take long for endoscopists to realize the value and the relative ease with which the colonoscope could be retroflexed in the rectum. This technique became widely used as a standard of the effectiveness of colonoscopy. In the retroflexion mode, the dentate line can be readily seen, usually in a 360° circumferential view; the mucosal junction between columnar mucosa and cuboidal mucosa of the anal canal is easily discernible; and at times, stratified squamous epithelium (external skin) can also be seen.

Over the years, rectal retroflexion became an integral feature of colonoscopy ( Fig. 1 ). Only recently has there been any investigation into its usefulness in discovering intrarectal pathologic conditions. This matter is of some controversy because some reports find that it has no additional pathologic findings, and others laud the benefits of this relatively simple maneuver.

Rectal retroflexion showing bulging hemorrhoids near anal verge. The white areas on hemorrhoids are caused by chronic prolapse.

As expected, it has been reported that rectal retroflexion is useful for the evaluation of hemorrhoids. However, 2 reports concluded that retroflexion in the rectum is a procedure with very little yield for perianal neoplasia. Saad and Rex successfully performed rectal retroflexion in 94% of 1502 patients and discovered only one small tubular adenoma not seen on forward examination. A previous article by Cutler and Pop inspected the rectal vault during scope withdrawal. They successfully performed the rectal retroflexion maneuver in 445 of 453 patients; they reported that this procedure yielded very little additional information because it revealed further findings in only 9 patients with 3 inflammatory pseudopolyps, 5 hyperplastic polyps, and one case of erosions.

In contrast, Varadarajulu and Ramsey found that more than 50% of the lesions in the rectal vault were identified only on retroflexion, with 30 out of 60 patients having significant additional information discovered by rectal retroflexion. There are several other similar reports and case studies espousing the value of rectal retroflexion.

Technique for rectal retroflexion

The technique of retroflexion has been described : “The rectum was first thoroughly examined on direct view upon withdrawal of the instrument up to the anal verge. The endoscope was then re-advanced into the rectum and the shaft of the instrument was rotated clockwise while both control knobs were fully angulated to invert the tip of the endoscope for a close view of the perianal rectal ampulla.” The maneuver was considered successful if a complete 360° visualization of the distal rectum was obtained. In this report, retroflexion was successful in 590 of 600 consecutive patients (98.3%). Because of a contracted vault, 10 patients could not have their retroflexion performed. It is interesting that endoscope-induced trauma was not encountered in any of the patients, although 9 patients who had successful retroflexion complained of rectal pain during the procedure.

The author’s technique is to carefully inspect the rectal mucosa down to the anal verge and then advance the colonoscope, placing the tip against a flat area of the mucosa at the level of the first rectal valve. The tip is then maximally deflected upward and gently advanced into the rectum. If resistance is encountered and the tip does not slide freely across the mucosa, the attempt is abandoned and another site is chosen for the retroflexion maneuver. The retroflexion attempt should be discontinued if patients complain of pain during the maneuver. It should not be attempted in the presence of a contracted small rectum such as occurs after radiotherapy or in inflammatory bowel disease. If the tip slides across mucosa easily (although a view of the lumen cannot be seen), the small outer dial control is then maximally deflected to the right and locked. The right hand, which moved and locked the small dial control, then grasps the instrument, and the scope is torqued markedly clockwise and withdrawn. This technique frees the tip from mucosal contact and affords a view of the shaft as it traverses the anal canal. The perianal area can be easily visualized by torque and withdrawal. It is not usually possible to retroflex the scope in the rectum by sole use of the dial controls, although these are effective to turn the tip into a retroflex position when the scope is outside of patients in a demonstration mode. The inability to freely retroflex in the rectum is caused by the radius of the tip deflection being greater than the spatial capacity of the rectal ampulla so that the tip is constrained and catches the wall, impairing free movement.

Complications with rectal retroflexion

Perforations related to rectal retroflexion have been reported that are generally caused by a contracted rectal vault or advancing the instrument against resistance. Saad and Rex made a point that this maneuver should not be attempted if the rectum seems narrow. There are 2 specific instances when rectal retroflexion should be avoided, and these are ulcerative colitis and after radiation treatment of prostate cancer when the rectal vault may be contracted.

Proximal colon retroflexion

A more thorough evaluation of the right colon has been popularized primarily because of recent reports showing that colon cancer can occur shortly following a negative colonoscopic examination and that colonoscopy may not protect against the development of right colon cancers.

Hewett and Rex were able to perform retroflexion in the right colon in almost 95% of patients in whom it was attempted, and an additional 10% of polyps were seen in addition to those discovered on forward view colonoscopy. Even with meticulous examination in the forward view, they missed 12% of large adenomas (≥1 cm) that were found on retroflexion.

In another study, a prototype tapered colonoscope with the distal 25 cm being similar to a pediatric-sized diameter tapering to a standard adult-sized colonoscope was compared with a standard pediatric variable-stiffness colonoscope. A retroflexion could be performed 98% of the time with the tapered scope as compared with 78% with the pediatric variable-stiffness colonoscope.

Two prototype instruments, one with a shorter bending section and the other with a tighter radius of tip deflection, showed a significantly higher rate of successful retroflexion compared with the standard pediatric colonoscope; there was no difference between them in the success rate of cecal retroflexion. The success of retroflexion in the cecum was 57% for the standard pediatric colonoscope and 91% and 94% for the prototype instruments.

Another study was performed with similar instruments but using adult-diameter colonoscopes.

The instrument with a shorter bending section could be retroflexed in the cecum more often than the other, but there were no other significant differences noted with either instrument.

An earlier report by the Indiana Group had shown disappointing results for additional adenoma detection from retroflexion in the right colon during screening colonoscopy. Following an initial examination, the cecum was then reintubated and the patients were randomized to a second examination either using a forward-viewing technique or using a retroflexed mode. It was found that the standard adult colonoscope could only be retroflexed in the cecum approximately 40% of the time, and a standard pediatric colonoscope could be retroflexed in the cecum approximately one-third of the time when attempted ( Fig. 2 ).

Retroflexion of pediatric-type colonoscope in the ascending colon. The proximal aspects of folds can be seen.

When the second examination was performed in the standard forward view, the miss rates for polyps and adenomas during the initial examination were 37% and 33%, respectively. When the second examination was performed with retroflexion, the rates of missed polyps and adenomas were 38% and 23%, respectively. Thus, the calculated miss rate on the second examination performed in retroflexion was numerically lower than when the second examination was performed in the forward view. The explanation proffered in this report was that the retroflexion does not expose the entire colon to view because the instrument may be difficult to maneuver during retroflexion or that polyps located in hidden positions on the proximal sides of folds are not the principal mechanism accounting for failure of detection during colonoscopy. Although no complications were seen during this randomized study, the investigators cautioned against routine retroflexion in the right colon because of the possibility of complications.

Retroflexion and polypectomy

Two articles have discussed the removal of colon polyps during retroflexion with a colonoscope ( [CR] ). Prototypes of the pediatric-type colonoscope (one with a shorter bending section and the other with a tighter tip deflection radius) were used in one of these studies. Standard polypectomy procedures were used to remove 59 consecutive large sessile polyps proximal to the rectum. Fourteen polyps were removed partially or completely in the retroflexion mode. There were no perforations and no complications related to retroflexion. The polyps removed in retroflexion could only barely be visualized in the forward view, and all could not have been removed except by using the retroflexion technique. A similar report detailed 15 polypectomies with endoscopic retroflexion. All of the polyps were sessile and large (average size 38 mm, range 20–60 mm) and evenly distributed throughout the colon. The procedures were performed using a standard Pentax colonoscope (EC3831L, Pentax Precision Instrument Corporation, Orangeburg, NY).

The authors of both reports state that retroflexion attempts should be stopped if the endoscopist feels resistance when bending the tip or when trying to advance the scope. Oftentimes, the use of an upper endoscope may be a good alternative especially when retroflexing in the left colon.

Use of a gastroscope

A gastroscope, which has both a short nose and a short bending section, has been reported to be easily retroflexed in the right colon so that flat polyps can be removed in the retroflexion mode. In an article by Hurlstone and colleauges, cecal intubation was achieved in 100% of cases using a gastroscope and all 76 patients had tumors that were situated on both sides of a fold, located on both the proximal and distal aspects. Endoscopic resection was possible in 61 patients who completed their protocol (8 were excluded by the endoscopic ultrasound criteria), with a 98% cure rate following endoscopic mucosal resection using a standard gastroscope. It is the opinion of the author of this article that although a gastroscope can often be passed to the cecum, it is not invariably the case because the length may be too short to allow advancement around several bends and folds of the colon, especially in tall or overweight patients.

Technique for retroflexion in proximal colon

This author’s technique is to advance the instrument several haustral folds beyond the polyp. Loops are removed by withdrawing the scope to straighten the instrument as much as possible. The dial controls are pointed maximally up and to the right. The right/left control is locked, and the thumb maintains the large control wheel in an upward direction. The scope is then advanced a few centimeters to determine whether the tip will begin to slide across the mucosal surface or whether a loop forms in the shaft. If the tip slides freely, further advancement of the scope is performed to complete the retroflexion. If the scope shaft is pushed in but the tip does not move, then a loop is forming and the scope should be torqued in a clockwise fashion and withdrawn.

Once retroflexion view is obtained, the instrument tip can be controlled by torque around several folds of the ascending colon and may be withdrawn into the transverse colon by gentle manipulation of the shaft, torquing it to the right or to the left as necessary to insinuate the tip around acute angulations near the hepatic flexure.

The recent interest in the retroflexion view of the colon has been engendered by the reported miss rate of the colonoscope and of the inability of colonoscopy to prevent right-sided colon cancer. Studies to measure the miss rate for colonoscopy have used several different methods.

Tandem colonoscopy

The concept of tandem colonoscopy is well suited for evaluation of missed lesions in the colon because polyps that are found are discrete, can be measured, are readily recognized, and are common. During tandem colonoscopy, the first examiner removes all polyps that are encountered so all polyps seen by the second endoscopy will represent overlooked lesions. One of the problems with tandem colonoscopy is that the endoscopists know they are part of a study and will pay special attention so as not to miss lesions. However, despite this heightened awareness from being part of a tandem colonoscopy experiment, trials that have evaluated the miss rate of polyps in the large bowel through performing a second-pass colonoscopy have revealed strikingly large numbers of polyps overlooked by the first examiner using the same standard colonoscopic equipment.

The first such study by Hixson and colleagues found a 15% miss rate for adenomas less than 1 cm in size. Rex and colleagues, in a study of 183 patients, reported a 27% miss rate for polyps smaller than 6 mm in diameter and only 6% for polyps larger than 9 mm. There was no significant difference in the miss rate of polyps in the right colon (27%) than in the left colon (21%). Although a substantial percentage (24%) of adenomas were missed, there was an inverse ratio between the miss rate and the size of the adenoma. In the summary of the report, the investigators recommended that technology be developed that may overcome the technical limitations of colonoscopy.

The more recent large multicenter European study found miss rates of 28% for all polyps, 31% for hyperplastic polyps, and 21% for adenomas. However, the miss rate for all polyps 5 mm or larger was 12% and 9% for adenomas. Among the 14 polyps and 6 adenomas larger than 5 mm missed during the first examination, 5 polyps and 1 adenoma were sessile, and 9 polyps and 5 adenomas were flat. In all, 37 adenomas were overlooked in 286 patients, with the median size being 3 mm; however, the range of missed lesions was from 1 to 18 mm. This report also stated that 3 advanced adenomas were missed whose size varied from 15 to 18 mm. The investigators reported that there was a 27% rate of missed adenomas for lesions less than 5 mm in diameter, whereas the miss rate for lesions greater than 5 mm in diameter was 9%.

The most recent back-to-back colonoscopy study for missed lesions involved special effort to ensure a “quality examination.” This involved eliminating cases whereby the cecum was not intubated or when the bowel prep was poor. The examinations were performed by 2 experienced colonoscopists who have previously performed more than 3000 colonoscopies, and the withdrawal time was more than 6 minutes in every case. The second colonoscopy was performed immediately after conclusion of the first examination by the same examiner. A total of 149 patients completed all the criteria for enrollment in the study whereby all polyps were removed during the initial examination. The miss rates (polyps found on the second examination) for all polyps, all adenomas, adenomas 6 to 9 mm, and advanced adenomas were 16.8%, 17.0%, 7.2%, and 5.4%, respectively. The location of polyps in the right or left colon did not significantly affect the miss rate, which was positively correlated with the size of the polyp.

Despite the attention to quality in this study, the true adenoma miss rate is not known because the second colonoscopy was used as the gold standard. Their conclusion was that a significant number of adenomas (17.0%) and advanced adenomas (5.4%) were being missed during colonoscopy and that “development of new endoscopic techniques to overcome the technical limitations of the current colonoscopic examination is important.”