Identifying the optimal bowel preparation for small-bowel capsule endoscopy: a meta-review and umbrella meta-analysis

Small-bowel (SB) capsule endoscopy (SBCE) is a well-established diagnostic tool in GI medicine. However, the optimal bowel preparation strategy remains uncertain. Although multiple systematic reviews and meta-analyses (MAs) have explored the efficacy of purgative regimens versus fasting-only protocols, their findings are often conflicting. This meta-review and umbrella MA aims to synthesize high-quality evidence and identify the most effective, safe, and standardized preparation approach for SBCE. The primary outcomes assessed were SB mucosal cleansing quality, diagnostic yield (DY), and procedure completion rate, comparing purgative regimens to fasting-only protocols. Secondary outcomes included SB transit time and the influence of preparation timing and fasting duration on procedural efficacy.

We performed a comprehensive systematic search of EMBASE, MEDLINE, and PubMed to identify systematic reviews, with or without MA, that compared purgative versus fasting preparation regimens in adult patients undergoing SBCE. The methodological quality of the included reviews was assessed using A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR-2). To evaluate the overlap between reviews, we applied the corrected covered area method. The certainty of evidence was appraised according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Due to substantial primary study overlap between systematic reviews, we conducted an umbrella MA by extracting and synthesizing data from all the unique primary studies included within the systematic reviews using a random-effects model.

Ten systematic reviews, comprising 53 unique primary studies, were identified, with a total of 9636 participants, 39 of which were included in the umbrella MA. Compared to fasting, purgative bowel preparation showed a significantly improved cleansing adequacy (risk ratio, RR, 1.24; 95% CI, 1.12-1.37), with polyethylene glycol (PEG) being the only laxative demonstrating a significant effect. Additionally, no difference in cleansing quality was observed between different volumes of PEG preparation. Regarding dosage timing, same-day dosing showed the greatest benefit in cleansing quality (RR, 1.75; 95% CI, 1.33-2.29), followed by postingestion regimens (RR, 1.59; 95% CI, 1.17-2.16). Purgatives offered marginal gains over fasting in DY (RR, 1.12; 95% CI, 1.00-1.24) and completion rate (RR, 1.02; 95% CI, 1.00-1.04), with a significant benefit seen in Crohn's disease-predominant studies (RR, 1.15; 95% CI, 1.11-1.20; I² statistic [a measure of heterogeneity] = 0%). Subgroup analysis again demonstrated a significant improvement in DY with same-day preparation (RR, 1.30; 95% CI, 1.07-1.57).

This study demonstrates that purgative bowel preparation, particularly with PEG, is superior to fasting alone in improving adequate SB cleansing and diagnostic accuracy. Notably, a same-day regimen significantly enhances both cleansing quality and DY, suggesting that the timing of administration is more critical than the laxative's dosage.