In Focus

Quality metrics in colonoscopy


Withdrawal time

Optimizing identification of colonic lesions requires a careful and thorough exam of the colon on withdrawal. While this may seem obvious, there is often little focus on the approach to withdrawal. In four chapters on colonoscopy technique from textbooks, the number of pages describing insertion ranged from 20 to 38, while the number of pages focused on withdrawal ranged from 0.5 to 1.5.11-14

Table 2. Proposed scoring system for withdrawal technique

A study examining the difference in withdrawal technique between two endoscopists who were known to differ in adenoma miss rates by tandem colonoscopy proposed the scoring system listed in Table 2 that can assess quality of examination on withdrawal. There was a statistically significant difference in quality scores for the two endoscopists, as assessed by expert review of video recordings of their colonoscopies.15

Dr. Aasma Shaukat

The endoscopist with the lower adenoma miss rate was also found to have an average withdrawal time of 8 minutes and 55 seconds versus 6 minutes and 41 seconds for the endoscopist with the higher adenoma miss rate. A large, community-based study with over 76,000 colonoscopies found a statistically significant correlation between interval colorectal cancer and withdrawal times shorter than 6 minutes.16 However, there was no association between ADR and colorectal cancer, suggesting that, for practices with optimal ADRs (that is, rates greater than 25%), withdrawal time may be a more sensitive marker of quality of colonoscopy than ADR is.16Intuitively, adequate examination of the colon that includes examining the proximal side of folds, washing and suctioning stool, and even repositioning the patient would likely increase withdrawal time. In a 2008 study examining 2,000 screening colonoscopies of 12 endoscopists, those with withdrawal times greater than 6 minutes had significantly higher rates of detecting adenomas and advanced neoplasia, compared with those with faster withdrawal times.17 The average ADR in this group was 28.3%, compared with 11.8% for physicians who had a withdrawal time less than 6 minutes.17 An evaluation of nearly 11,000 colonoscopies done by 43 endoscopists also identified an increase polyp yield with increased withdrawal time.18 These data drive the recommendation for a minimum withdrawal time of 6 minutes, with 2 minutes spent examining each colonic segment.

Bowel preparation

Diagnosis of colonic lesions is dependent on adequate visualization of the colon. Poor bowel preparation can limit the yield of colonoscopy and lead to missed lesions. It also leads to canceled and rescheduled procedures that reduce efficiency, increase cost, and pose an undue burden on the patient.

The quality of bowel preparation should be assessed after washing and suctioning of colonic mucosa has been completed. Adequate preparation is that which allows identification of lesions greater than 5 mm in size.19

Table 3. Boston Bowel Preparation Score

Quality of preparation is assessed subjectively by the endoscopists and often listed as excellent, good, fair, or poor. An alternative method of reporting bowel preparation quality is the Boston Bowel Preparation Score (BBPS) (Table 3).20 This scoring system allows for a more descriptive assessment of each colonic segment by assigning a score from 0 to 3 for the right, transverse, and left colon, leading to a total score between 0 and 9. The BBPS also helps standardize reporting of bowel preparation. The polyp detection rate associated with a BBPS of 5 or greater was 40%, compared with 24% associated with BBPS less than 5.19 A split-dose bowel preparation regimen with at least half of the preparation ingested on the day of the procedure is recommended to optimize quality of bowel preparation.6

The American Society for Gastrointestinal Endoscopy and American College of Gastroenterology task force on quality assurance in endoscopy recommends that bowel preparation should be adequate in 85% of all colonoscopy exams on a per-provider basis.7 One study of completed colonoscopy with inadequate preparation showed an adenoma miss rate of 48%.21 In the setting of inadequate bowel preparation, another study reported 42% of all adenomas detected were only found on repeat colonoscopy. When considering advanced adenomas, there was a 27% miss rate, a relatively high percentage.22

When poor bowel preparation precludes the exam, colonoscopy is appropriately aborted, and the patient asked to return. However, there are situations in which the exam can be completed but the bowel preparation is still inadequate to identify polyps larger than 5 mm. In this setting, the colonoscopy should be repeated with a more aggressive bowel preparation regimen within 1 year.19 Shorter intervals are recommended if advanced neoplasm is detected within an inadequate bowel preparation.19

The appropriate surveillance interval can be unclear when bowel preparation is considered adequate to identify polyps greater than or equal to 5 mm, yet still suboptimal. “Adequate” or “fair” bowel preparation often leads to shorter-than-recommended surveillance intervals because of the concern for small missed lesions. For example, patients with normal colonoscopy results and a fair prep were recommended to undergo a screening colonoscopy in 5 years at 57.4%, while only 23.1% received a 10-year recommendation.23 This increased frequency of colonoscopy leads to increased costs and procedural risks for the patient. Furthermore, a meta-analysis evaluating the effects of bowel preparation reported no significant difference in ADR between adequate and excellent prep.24 These findings suggest that patients with adequate bowel preparation may be followed at guideline-recommended surveillance intervals without significantly affecting colonoscopy quality as measured by ADR.

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