Doctors who took longer to evaluate a patient's colon were almost four times as likely to spot one particular type of growth, according to the study.
In a colonoscopy, the doctor guides a thin, flexible tube with a tiny camera through the colon.
The colonoscopy camera lets the doctor check the colon for abnormalities, including cancerous and precancerous growths.
The new study, published in The New England Journal of Medicine, found that colonoscopies that took longer flagged more abnormal growths than quick colonoscopies.
The findings come from Robert Barclay, MD, and colleagues at the University of Illinois College of Medicine in Rockford, Ill.
Barclay's team analyzed more than 7,800 colonoscopies done by 12 gastroenterologists from January 2003 through March 2004.
The gastroenterologists worked at the same Rockford gastroenterology practice as Barclay and most of the researchers.
The doctors were board certified and experienced, having done more than 3,000 colonoscopies before the study.
The patients involved were generally at "average risk" for colon cancer, write the researchers.
On average, it took seven minutes for a doctor to guide the colonoscopy device to the top of the colon during the procedure, and another six minutes to withdraw it as he evaluated the inside of the colon.
If the doctor stopped to remove an abnormal growth, withdrawal took four extra minutes, on average.
The study's key finding: Slower withdrawal of the device appears to result in a more thorough colonoscopy.
Doctors who spent more than six minutes withdrawing the colonoscopy tube found more abnormal growths than those who withdrew it in less than six minutes, according to the study.
For instance, the detection rate for one particular type of growth, called an adenoma, was "nearly four times as great" among doctors who took more time withdrawing the tube.
How long should a doctor spend withdrawing the tube? The study doesn't settle that question.
While other experts have suggested six to 10 minutes, Barclay's team doesn't make a specific time recommendation.
"Longer procedure time does not necessarily mean higher quality," David Lieberman, MD, says in a Journal editorial. "However, the results of this study are intuitive."
Lieberman works in Portland, Ore., at the gastroenterology department of Oregon Health and Science University and the Portland Veterans Affairs Medical Center.
Careful colon examination should boost the adenoma detection rate, "which is an important indicator of quality," says Lieberman.
SOURCES: Barclay, R. The New England Journal of Medicine, Dec. 14, 2006; vol 355: pp 2533-2541. Lieberman, D. The New England Journal of Medicine, Dec. 14, 2006; vol 355: pp 2588-2589.
By Miranda Hitti
Reviewed by Brunilda Nazario