Colonoscopy withdrawal times linked to polyp detection rates

"There has been controversy over whether longer withdrawal times could lead to detection of increased numbers of polyps of various types," said Lynn F. Butterly, MD, director of Colorectal Cancer Screening at Dartmouth-Hitchcock Medical Center and NCCC, and associate professor of Medicine at the Geisel School of Medicine at Dartmouth. "Since the rate of discovery of polyps is a critical quality measure for colonoscopy, examining whether or not there is an association between withdrawal time and finding more polyps may contribute evidence leading to improved quality in screening through colonoscopy."

During a colonoscopy, a lighted tube (colonoscope) is passed through the colon to find and remove polyps. The colonoscope is passed to the area where the large and small intestine meet, and the scope is then slowly withdrawn back through the colon, carefully examining the lining. The time spent in withdrawing the scope and doing a detailed examination is called the withdrawal time.

Colorectal cancer (CRC) is the second most common cause of death from cancer in the US, but CRC is preventable through screening. Most CRC begins as a small growth on the lining of the colon, known as a polyp. Over a period of several years, some polyps may turn into cancer.

Using data from the New Hampshire Colonoscopy Registry (NHCR), the authors examined how endoscopists' withdrawal time in normal, well-prepped colonoscopies affected their polyp detection rates. They analyzed 7,996 colonoscopies performed in 7,972 patients between 2009 and 2011 by 42 endoscopists at 14 hospitals, ambulatory surgery centers, and community practices. Polyp detection rates were calculated based on median withdrawal time in normal exams.

"Our investigation demonstrates a statistically significant correlation between longer normal withdrawal time and higher (overall) polyp detection rates, adenoma detection rates, and serrated polyp detection rates, and provides strong evidence to support a 9-minute median normal withdrawal time as a quality standard," Butterly said.