Failure to visualize the cecum is more common for colonoscopies performed in the afternoon than for those performed in the morning, new research indicates.
While much of the increased failure rate is due to a higher risk of inadequate bowel preparation for afternoon colonoscopies, the failure rate remains elevated even after adjusting for this factor. Lead author Dr. Madhusudhan Sanaka told Reuters Health that he believes "it may simply relate to increased operator fatigue in the afternoon."
According to Dr. Sanaka, a gastroenterologist at MetroHealth Medical Center in Cleveland, previous studies have identified "a number of factors such as poor bowel preparation and female gender that are predictive of colonoscopy failure." He added that other studies have made the association between failure of the procedure and time of day, but it was unclear if this was simply a factor of poor bowel preparation.
The present study, reported in the
American Journal of Gastroenterology for December, involved 2087 colonoscopies that were performed at the researchers' center between November 2003 and October 2004. Roughly half of the procedures were performed in the morning and half in the afternoon.
All of the subjects were instructed to use a polyethylene glycol electrolyte-based bowel preparation the evening before the scheduled procedure day, the report indicates.
No significant differences were noted between morning and afternoon colonoscopy patients in terms of established failure risk factors.
The colonoscopy failure rate for the afternoon group was 6.5%, significantly higher than the 4.1% rate seen in the morning group (p = 0.013).
Inadequate bowel preparations were more likely in the afternoon group: 19.7% vs. 15.4% (p = 0.011). However, as noted, the failure rate in the afternoon group remained higher (5% vs. 3.2%) even after excluding the effect of poor bowel preparation.
Ideally, performing all colonoscopies in the morning might substantially reduce the number of patients needing a repeat procedure, Dr. Sanaka said. However, this is probably not feasible at most centers given the sheer number of patients undergoing the procedure.
Therefore, he suggested that perhaps established risk factors for colonoscopic failure could be used to "identify patients who should be scheduled for colonoscopy in the morning rather than in the afternoon."
Am J Gastroenterol 2006;101:2726-2730.
