When bowel preps are not good, doctors may miss almost half of adenomas (polyps) during colonoscopy. Worse, they may miss nearly 1 in 3 large adenomas, the most worrisome kind.
The bad news is that bowel prep may be suboptimal in as many of one in four patients.
Because of the danger of missing an adenoma after poor bowel prep, some doctors will repeat the colonoscopy, particularly if they found at least one adenoma during the first exam.
Doctors at Columbia University Medical Center reviewed all colonoscopies done there from 2006 to 2008, as well as colonoscopies that were repeated within three years.
Of nearly 13,000 colonoscopies, over 3,000 had suboptimal preparation, either fair or poor. Five hundred of those were repeated during the three year follow-up. In the 216 with good preparation for the second exam, 196 adenomas were found in all, 83 only on the second test, an adenoma miss rate of 42%. The miss rate for advanced adenomas was 27%.
For colonoscopies that were repeated within a year, the miss rate for all adenomas was 35% and for advanced adenomas 35%.
Although only a fraction of patients with poor preps had their exams repeated, the additional polyps which were probably missed on the first test were a serious problem.
Dr. Benjamin Lebwohl, who led the study, said,
Our findings of a miss rate of 42 percent for all adenomas and 27 percent for advanced adenomas suggest that suboptimal bowel preparation has a substantial harmful impact on the effectiveness of colonoscopy, and follow-up examination within one year should be considered. Because neoplastic findings on the initial colonoscopy were associated with a greater miss rate, a repeat examination within one year is indicated when an adenoma is found during a colonoscopy with suboptimal bowel preparation
What This Means for Patients.
Following the directions for getting ready for a colonoscopy is very important.
Be sure that
- You keep to diet recommendations including clear liquids the day before your test.
- You understand the laxative plan that will be used to clean your colon and have the prep on hand the day before your exam.
- You drink plenty of clear liquids during your bowel prep.
- You call your doctor right away if your can’t finish the prep because of nausea, vomiting, pain, or any other reason. A different regimen may be prescribed that you can finish.