Performance of Screening Colonoscopy in Everyday Practice

David A. Johnson, MD, FACG, FACP


January 19, 2007

Colonoscopic Withdrawal Times and Adenoma Detection During Screening Colonoscopy

Barclay RL, Vicari JJ, Doughty AS, Johanson JF, Greenlaw RL
N Engl J Med. 2006;355:2533-2541

Colorectal cancer (CRC) screening using colonoscopy has become a standard of care in the United States. This application of colonoscopy has been predicated on the enhanced ability (over other diagnostic screening tests for CRC) of this modality to detect both cancerous and precancerous lesions, as well as on its ability to detect and remove precancerous polyps. Indeed, the accurate detection and removal of precancerous lesions are key to the value of colonoscopy. Although there have been observations suggesting that shorter colonoscope withdrawal times are associated with higher miss rates for adenoma detection, this factor has not been studied in a large prospective trial.

The aim of this current study was to determine whether longer periods for instrument withdrawal from the cecum would correspond to higher detection rates of precancerous adenomas. This study was conducted by a relatively large group of community-based gastroenterologists, all of whom were very experienced in the performance of colonoscopy. Each physician had performed a minimum of 3000 colonoscopies prior to this study.

During a 15-month period, a total of 7882 colonoscopies were performed by 12 gastroenterologists in a busy, community-based private practice setting. Of these exams, 2053 were performed for CRC screening and these exams were the basis of the study analysis. The endoscopists were aware that a study examining colonoscopy techniques and procedure time was being conducted. The withdrawal time from the cecum was defined as time taken for the exam and any maneuvers, such as biopsy or polypectomy. The mean time for withdrawal with and without biopsy/polypectomy was 6.3 +/= 3 and 10.6 +/= 5.8 minutes, respectively. Adenomatous polyps were detected in 23.5% of screened patients. Advanced neoplasms (≥ 1 cm, villous histology, high-grade dysplasia, or cancer) were found in 5.2% of patients.

There was a strong correlation between withdrawal times and adenoma detection rates. Compared with endoscopists with mean withdrawal times of 6 or more minutes, endoscopists with mean withdrawal times of less than 6 minutes demonstrated a lower detection for any neoplasia (11.8% vs 28.3%; P < .001) and for advanced neoplasia (2.6% vs 6.4%; P = .005).

This study has received a great deal of attention from the press, and its findings are somewhat intuitively obvious. If physicians take a longer time to perform a colonoscopy, they should likely give a more comprehensive exam. However, time is not the only key factor; a quality exam is affected by several factors. First, the exam must be performed by a quality endoscopist who is skilled and trained to perform colonoscopy. Additionally, a thorough exam requires a good-to-excellent colon purgative preparation of the patient. Efforts should be made during the exam to clear any area with fecal residue, and to efface and look behind colonic folds. Newer optical imaging methods with enhanced magnification and imaging ability to evaluate subtle mucosal derangements should also help in the detection of flat polyps that may be difficult to identify. Recognizably, these study findings will need to be validated in multicenter trials involving larger groups of endoscopists, and these studies are already being planned. Efforts to optimize the quality of exams, as suggested by this study, should maximize our potential to affect the long-term outcome of the prevention of CRC.



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