Safety and Efficacy of the 'One-Cup, Two-Cup Method' for Oral Sulfate Solution Administration in Colonoscopy Preparation: A Prospective Multicenter Study

Aims The oral sulfate solution (OSS) is a hypertonic bowel preparation solution used as a premedication for colonoscopy, requiring adequate water intake post-administration to prevent dehydration. The standard method for OSS administration (OSS 480 mL+1000 mL water, with additional doses of OSS 240 mL+500 mL water as needed) has been previously studied. This study evaluated whether the 'One-Cup, Two-Cup Method'(OSS 120 mL+240 mL water, repeated until clear effluent is achieved) can reduce solution volume and preparation time compared to the standard OSS administration protocol while maintaining adequate bowel cleansing efficacy.

Methods This prospective, single-arm study was conducted at four medical institutions in Japan from August 2023 to October 2024, examining the safety and efficacy of OSS administered using the One-Cup, Two-Cup Method in 275 cases. Bowel cleansing was evaluated using a five-point scale: 1=Almost no residual stool in the colon, allowing good observation; 2=Some residual stool that does not impede observation; 3=Observation impeded by residual stool; 4=Observation impossible due to a large amount of residual stool; 5=Undeterminable. Effective bowel preparation was defined as a score of 1 or 2 across all five segments of the colon (cecum/ascending, transverse, descending, sigmoid colon, and rectum). Surveys assessing the willingness to continue using OSS were conducted among all patients and 58 nurses, with each item rated on a four-point scale.

Results Among the participants, 182 were male and 93 female, with a mean age of 58 (range: 25–79). The overall effectiveness rate was 71%, with regional ineffective rates as follows: cecum/ascending 26%, transverse 15%, descending 8%, sigmoid 7%, and rectum 6%. The mean preparation time was 134 minutes (range: 60–360), with an average of 689 mL (range: 360–960) of OSS solution and 1424 mL (range: 750–2500) of water consumed. No clinically significant adverse events related to OSS administration were reported. Survey results indicated that 85% (236/275) of patients and 87.9% (51/58) of nurses expressed their willingness to continue using this method of OSS administration.

Conclusions The One-Cup, Two-Cup Method with OSS reduced preparation time and solution volume. Cleansing efficacy was overall sufficient for effective colonoscopy. No clinically significant adverse events were observed. Both patients and nurses showed high acceptance of the method.

Publication History

Article published online:
27 March 2025