Retroflexion of the sigmoidoscope for the detection of rectal cancer

Author: Edward J. Esber, Peter Yang
Date: May 15, 1995

Flexible sigmoidoscopy is a procedure that is commonly used by primary care physicians for the evaluation of rectal disorders and for colorectal screening. Retroflexion of the endoscope improves views of the anorectum and rectal vault, which increases the diagnostic yield of sigmoidoscopy. We report three cases of rectal lesions that were not detected when flexible sigmoidoscopy was performed without retroflexion. The lesions were all malignant or premalignant. The illustrative cases demonstrate the value of retroflexion in flexible sigmoidoscopy for the detection of rectal lesions.

The rectum is a frequent site of occurrence of adenocarcinoma. Approximately 15 to 20 percent of colon cancers and polyps with malignant potential are located in the rectum.[1,2] Clinical manifestations of rectal carcinoma include bleeding, constipation, tenesmus and weight loss. These symptoms also commonly occur in patients with benign disorders.

Several methods are used to detect rectal lesions, including digital rectal examination, barium enema, anoscopy and flexible sigmoidoscopy. In addition to detecting rectal polyps, a 65-cm flexible sigmoidoscope can detect 60 percent of colon cancers.[1] Recent data have demonstrated the benefit of screening and of removal of rectal polyps in the prevention of colorectal cancer.[3,4] Flexible sigmoidoscopy is used commonly by primary care physicians and is a routine component of most internal medicine and family practice training programs.

Retroflexion of the sigmoidoscope improves views of the rectum and the anorectal junction. This maneuver is performed in three steps, usually just before completing the sigmoidoscopic examination: first, the scope is withdrawn to the anal verge, completing the forward-viewing examination, and then the tip is placed approximately 10 cm into the rectum; second, while advancing the scope 5 to 10 cm, the tip is deflected upward 180 degrees, and third, the scope is rotated on the longitudinal axis, providing circumferential views of the anorectum. Slight withdrawal of the retroflexed scope brings the anal verge into closer view. Retroflexion may cause discomfort or the sensation of rectal fullness in some patients, but it is usually well tolerated.[5]

The following three cases of rectal lesions were initially undetected during insertion and withdrawal of the sigmoidoscope but were subsequently seen on retroflexion. Grobe and colleagues[5] prospectively evaluated the benefit of retroflexion in 75 patients undergoing flexible sigmoidoscopy and colonoscopy. The diagnostic yield of colonic lesions was increased 8 percent with retroflexion, compared with simple withdrawal of the scope. Our experience further emphasizes the value of retroflexion in the detection of rectal pathology.

Illustrative Cases


A 42-year-old man presented with a two-year history of loose, mucous stools, occasionally mixed with blood. Bowel frequency had been three stools per day. The patient did not have abdominal pain or weight loss. He had a positive family history for colon cancer, which had occurred in his grandfather. Flexible sigmoidoscopy performed by the patient's internist two years before this presentation showed white plaques consistent with possible colitis. At the present examination, colonoscopy showed normal mucosa throughout the entire colon. However, retroflexed views demonstrated a circumferential mass involving half of the rectal lumen. Results of biopsy revealed adenocarcinoma with focal transitional cell features. The patient underwent abdominoperineal resection of the tumor. The final pathologic diagnosis was moderately differentiated adenocarcinoma.


A 56-year-old man with a history of hemorrhoids and rectal bleeding underwent flexible sigmoidoscopy performed by his family physician. The procedure showed a polyp at 20 cm, which was confirmed by colonoscopy. Retroflexed views revealed a 2-an polyp at the anorectal junction, which had not been previously noted. Biopsies of both polyps were performed. The lesion at 20 cm was a tubular adenoma, and the rectal lesion was a tubulovillous adenoma. The patient underwent transrectal excision. The pathologic diagnosis was tubulovillous adenoma.


A 71-year-old man with a history of guaiac-positive stools underwent flexible sigmoidoscopy performed by his family physician. Results of the test were unremarkable. A follow-up barium enema showed a rectal polyp. Colonoscopy showed several diverticula and a large polyp best visualized on retroflexion (Figure 1). The pathologic report of the polyp indicated tubulovillous adenoma. The polyp was removed transrectally without difficulty. The final pathologic diagnosis was vinous adenoma, with focal severe peripheral dysplasia.


These three cases demonstrate the value of retroflexion when performing fiberoptic sigmoidoscopy or colonoscopy. The patients in this report underwent initial sigmoidoscopy that did not detect rectal lesions that were readily identified when colonoscopy was repeated with retroflexion. All of the lesions found were malignant or premalignant.

Before the widespread use of flexible fiberoptic sigmoidoscopy and colonoscopy, most rectal lesions were detected by digital rectal examination and rigid proctosigmoidoscopy. A digital rectal examination is routinely performed before insertion of the sigmoidoscope, which provides lubrication to the anal canal and excludes the presence of an obstructing lesion that would prevent the insertion or passage of the endoscope. Two of the three lesions detected in this report were villous adenomas that were accessible on routine digital examination. Since these tumors frequently have a velvety soft texture when palpated, they may be mistaken for normal mucosa.

Fiberoptic flexible sigmoidoscopy is a procedure that can be easily learned.[6-8] Most authors agree that performing 20 to 25 supervised sigmoidoscopies provides adequate training.[9] Instruction in flexible sigmoidoscopy is included routinely in family practice and internal medicine residency programs. Retroflexion of the sigmoidoscope should be an integral aspect of this training.

In addition to digital rectal examination, retroflexion of the sigmoidoscope should be performed during every flexible sigmoidoscopy to increase the diagnostic yield of rectal lesions.


[1.] Devesa SS, Chow WH. Variation in colorectal cancer incidence in the United States by subsite of origin. Cancer 1993;71:3819-26. [2.] Granqvist S. Distribution of polyps in the large bowel in relation to age. A colonoscopic study. Scand J Gastroenterol 1981;16:1025-31. [3.] Winawer SJ, Zauber AG, Ho MN, O'Brien MJ, Gottlieb LS, Sternberg SS, et al. Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup. N Engl J Med 1993;329:1977-81. [4.] Selby JV, Friedman GD, Quesenberry CP Jr, Weiss NS. A case-control study of screening sigmoidoscopy and mortality from colorectal cancer. N Engl J Med 1992;326:653-7. [5.] Grobe JL, Kozarek RA, Sanowski RA. Colonoscopic retroflexion in the evaluation of rectal disease. Am J Gastroenterol 1982;77:856-8. [6.] Hocutt JE Jr, Jaffe R, Owens GM, Walters DT. Flexible fiberoptic sigmoidoscopy. Am Fam Physician 1982;26(5):133-41. [7.] DiSario JA, Sanowski RA. Sigmoidoscopy training for nurses and resident physicians. Gastrointest Endosc 1993;39:29-32. [8.] Schertz RD, Baskin WN, Frakes JT. Flexible fiberoptic sigmoidoscopy training for primary care physicians: results of a 5-year experience. Gastrointest Endosc 1989;35:316-20. [9.] Hawes R, Lehman GA, Hast J, O'Connor KW, Crabb DW, Lui A, et al. Training resident physicians in fiberoptic sigmoidoscopy. How many supervised examinations are required to achieve competence? Am J Med 1986;80:465-70.

The Authors

EDWARD J. ESBER, M.D. is serving a fellowship in gastroenterology at MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland. Dr. Esber attended medical school at the Medical College of Ohio, Toledo. He completed an internship and a residency in internal medicine at the Virginia Commonwealth University Medical College of Virginia, Richmond. Dr. Esber was chief resident at the Mount Sinai Medical Center in Cleveland while serving as a clinical instructor at the Cleveland at the Case Western Reserve University School of Medicine.

PETER YANG, M.D. attended medical school at Johns Hopkins University School of Medicine, Baltimore. He completed an internship and a residency in internal medicine at New England Medical Center Hospitals, Boston. Dr. Yang received his gastroenterology training at Johns Hopkins Hospital. He is assistant clinical professor in gastroenterology at Case Western Reserve University School of Medicine.

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