Difficult colonoscopy: air, carbon dioxide, or water insufflation?

Background/Aims: This study aimed to compare tolerance to air, carbon dioxide, or water insufflation in patients with anticipated difficult colonoscopy (young, thin, obese individuals, and patients with prior abdominal surgery or irradiation). Methods: Patients with body mass index (BMI) less than 18 kg/m(2) or more than 30 kg/m(2), or who had undergone previous abdominal or pelvic surgeries were randomized to air, carbon dioxide, or water insufflation during colonoscopy. The primary endpoint was cecal intubation with mild pain (less than 5 on visual analogue scale [VAS]), without use of sedation. Results: The primary end point was achieved in 32.7%, 43.8%, and 84.9% of cases with air, carbon dioxide and water insufflation (P<0.001). The mean pain scores were 5.17, 4.72, and 3.93 on the VAS for air, carbon dioxide, and water insufflation (P<0.001). The cecal intubation rate or procedure time did not differ significantly between the 3 groups. Conclusions: Water insufflation was superior to air or carbon dioxide for pain tolerance. This was seen in the subgroups with BMI <18 kg/m(2) and the post-surgical group, but not in the group with BMI >30 kg/m(2).