A Prospective Randomized Study to Predict Bowel Preparation Quality Prior to Colonoscopy: Comparison of Two Stool Collection Methods for the Objective Assessment of Final Rectal Effluent Clarity

<b>Background/Objectives</b>: Adequate bowel preparation is essential for high-quality colonoscopy. The clarity of the final rectal effluent can predict its sufficiency and guide additional preparation if necessary. For an objective and reliable clarity assessment, the stool collection method may be as important as the evaluation itself. This study was designed to compare the sensitivity of clarity assessments of effluent collected using two methods: a disposable cardboard bedpan with a white bag (Group I) and a 50 mL transparent plastic container (Group II). <b>Methods</b>: A prospective, single-center, randomized, comparative study was conducted between August 2024 and January 2025. Based on predefined criteria, 37 of 177 randomized patients were excluded, and 140 were analyzed. <b>Results</b>: Inadequate bowel preparation was correctly identified by a team member in 71% of Group I and 23% of Group II (<i>p</i> = 0.033). In adequate cases, the detection sensitivity was 88% and 85% (Groups I and II, respectively; <i>p</i> = 0.854). Significantly more patients in Group II either withdrew or failed to submit a photograph of the final rectal effluent. Patients' verbal assessments did not differ significantly between the groups, regardless of bowel preparation quality. <b>Conclusions</b>: Patient self-assessment was an unreliable indicator of bowel cleanliness, highlighting the need for objective, standardized pre-colonoscopy evaluation methods. The use of a disposable cardboard bedpan with a white bag to collect the final rectal effluent may improve the accuracy of predicting inadequate preparation and patient compliance and may allow timely adjustments to bowel cleansing prior to colonoscopy in routine endoscopy practice.