Inadequate Bowel Preparation Associated With Missed Adenomas

Joe Barber Jr, PhD

March 29, 2012

March 29, 2012 — Inadequate bowel preparation commonly results in missed adenomas and other high-risk lesions during colonoscopy screening in average-risk patients, according to the findings of a retrospective chart review performed by Reena V. Chokshi, MD, and colleagues from Washington University in St. Louis, Missouri. Their findings were published online March 1 in Gastrointestinal Endoscopy.

The authors note the dangers of inadequate bowel preparation, especially in light of the lengthy follow-up intervals recommended for many patients: "Although follow-up intervals may be shortened, patients often do not undergo repeat colonoscopy for up to 3 to 5 years after the inadequate colonoscopy," the authors write. "If significant advanced adenomas were missed during that initial examination, waiting several years may result in the development of malignant lesions."

Past studies have shown that up to 25% of patients have inadequate bowel preparation at the time of their colonoscopy, yet the implications of poor preparation on polyp and adenoma detection have not been examined. Therefore, Dr. Chokshi and colleagues reviewed the charts of average-risk patients who underwent examinations (completed at least to the cecum) at their institution between 2004 and 2009, and for whom the bowel preparation was graded as poor, inadequate, or unsatisfactory, according to the 4-option Aronchick scale.

Among the 373 patients identified, the total number of missed adenomas was 91, resulting in a per adenoma miss rate of 47.9%.

The authors excluded patients with a history of inflammatory bowel disease, a family history of colorectal cancer, or a history of colon polyps. Regression analysis evaluated the association between adenoma detection and endoscopic technology or trainee participation, and the multivariate models were adjusted for age, sex, endoscopic technology, and trainee involvement.

The adenoma detection rate in the initial colonoscopies was 25.7%, including rates of 32.0% among men and 21.1% among women. Among the 133 patients who underwent repeated colonoscopy, at least 1 adenoma that was missed in the initial colonoscopy was detected in 33.8% of patients, including rates of 42.9% among men and 27.1% among women.

In the multivariate analysis, high-definition technology (odds ratio [OR], 1.30; 95% confidence interval [CI], 0.79 - 2.14; P = .30) and trainee involvement (OR, 1.40; 95% CI, 0.83 - 2.36; P = .21) were not associated with the overall adenoma detection rate. The limitations of the study included its retrospective nature, the inclusion of all repeated colonoscopies irrespective of quality, and the low percentage of patients undergoing repeat colonoscopy.

Despite these limitations, the authors suggest that changes are needed in the clinical approach: "Based on our findings that the majority of missed adenomas were in the proximal colon, a reasonable approach to the patient with inadequate bowel preparation on initial colonoscopy would be to abort the procedure, rather than subject the patient to the risk of a full colonoscopy that may result in missed adenomas," the authors write. "In this situation, colonoscopy should then be repeated as soon as possible in order to complete the examination."

The authors have disclosed no relevant financial relationships.

Gastrointest Endosc. Published online March 1, 2012. Abstract


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