BackgroundCatheter-related bladder discomfort (CRBD), secondary to catheterization of urinary bladder is distressing. The aim of this study was to assess the efficacy of preoperative education on CRBD with image illustration for alleviating CRBD.MethodsSixty adult male patients, undergoing elective colonal and rectal surgery, were randomized to receive tetracaine mucilage instilled into the urethra and applied to the catheter (tetracain group), or receive tetracaine mucilage in combination with image illustration on CRBD (image group) before urethral catheterization. The incidence and severity of CRBD were assessed at 0.5, 1, 2, and 6 h after patients’ extubation. The severity of postoperative pain, incidence of postoperative agitation and other adverse events were also recorded.ResultsPatients in image group reported remarkably less CRBD than those in tetracaine group at 0.5,1, 2 and 6 h after extubation (20, 20, 6.7 and 6.7% v.s. 60, 73.3, 53.3 and 53.3%, respectively, P<0.01). Severe CRBD was not reported in either group. However, the incidence of moderate CRBD was significantly lower in image group, with 6.7% at 1 h and thereafter none occurred, compared to 6.7% at 0.5 h, and increasing to 20% at 1 h, 2 h and 6 h in tetracaine group, respectively. Moreover, patients in image group suffered less moderate to severe postoperative pain than that of tetracaine group (13.3% v.s. 40.0% at 1 h, P = 0.039, 33.3% v.s. 60% at 2 h and 6 h, P = 0.038).ConclusionsPreoperative education on uretheral catheterization via image illustrations could enhance the effect of tetracaine mucilage in reducing both the incidence and severity of CRBD.Trial registrationThe trial was registered at www,clinicaltrials.gov with registration number NCT03199105 (retrospectively registered). Date of trial registration which is “June 26, 2017”.Electronic supplementary materialThe online version of this article (10.1186/s12871-018-0653-y) contains supplementary material, which is available to authorized users.