Objective      To determine the effect of warm water infusion instead of air insufflation on unsedated difficult colonoscopy.       Methods      One hundred and thirty-four outpatients with difficult colonoscopy that was defined as cecal intubation failure by trainees were randomly divided into a warm water infusion group (water group) and a traditional air insufflation group (gas group). The cecal intubation rate and abdominal pain scores were compared between the water group and the gas group.       Results      There was no significant difference in the age

sex

abdominal surgery history

constipation and body mass index (BMI) between the water group and the gas group. The cecal intubation rate of the water group (94.03%

63/67) was significantly higher than that of the gas group (79.10%

53/67) (P=0.021). The abdominal pain score of the water group (3.33±1.60) was significantly lower than that of the gas group (4.74±1.74

P=0.000).       Conclusion      Warm water infusion instead of air insufflation can improve the cecal intubation rate and reduce the abdominal pain during unsedated difficult colonoscopy.