Bowel Preparation for Flexible Sigmoidoscopy
Most flexible sigmoidoscopy procedures require bowel preparation, typically in the form of one or two sodium phosphate enemas administered 1 hour before the procedure. 1
Recommended Preparation Options
- Sodium phosphate enemas are the most commonly used preparation method for flexible sigmoidoscopy, with one enema administered 1 hour before the procedure being sufficient in most cases 1, 2, 3
- For patients at higher risk of inadequate preparation, two sodium phosphate enemas (one administered 3 hours before and another 1 hour before the procedure) may be considered, though studies show similar adequacy rates between one and two enema regimens 2, 3
- An alternative preparation with superior results combines oral magnesium citrate the evening before, clear liquids on the day of the procedure, and two Fleet enemas 1 hour before the procedure 4
- Self-administered Fleet enemas have been shown to provide superior bowel preparation compared to oral preparations like Picolax, with fewer adverse symptoms and higher patient acceptability 5
Quality Assessment
- The flexible sigmoidoscopy procedure report should document the quality of preparation and any impairment in visualization 1
- An adequate examination is one that allows confidence that mass lesions other than small (<5 mm) polyps are not obscured by the preparation 1
- Adequate colonic distension, suctioning, cleaning, and time spent examining the colonic mucosa correlate with higher detection rates 1
Management of Inadequate Preparation
When preparation quality is suboptimal, the endoscopist should make adequate arrangements for follow-up, including: 1
- Repeating the examination with a modified preparation
- Shortening the interval between screening examinations
- Pursuing an alternative screening strategy, such as fecal occult blood testing or double contrast barium enema
If the descending colon, sigmoid colon, and rectum are well-visualized during a screening procedure with otherwise inadequate preparation, it is reasonable to consider the limited examination as a flexible sigmoidoscopy 1
Special Considerations
- For patients at high risk of inadequate bowel preparation (e.g., history of constipation, use of opioids, diabetes mellitus), consider additional bowel purgatives 6
- Avoid unnecessary dietary restrictions beyond one day before the procedure, as additional days of dietary restrictions confer no benefit in bowel preparation adequacy 6
- A low-residue/low-fiber diet for early and midday meals on the day before the procedure, followed by clear liquids for the evening meal, is recommended 6
Potential Complications
- Perforation related to flexible sigmoidoscopy is rare, occurring in approximately 1 in 25,000-50,000 examinations 1
- The risk of major post-polypectomy bleeding is less than 1% 1
- Caution should be exercised with oral osmotic agents to avoid electrolyte disturbances and dehydration, particularly in elderly patients and those taking diuretics 1
Flexible sigmoidoscopy with adequate preparation has been shown to reduce colorectal cancer mortality, with a specific mortality benefit for distal colorectal cancer 1.