Ethical approval and trial registration: The trial was conducted between December 2017 and April 2018 in the Beijing Tongren Hospital in Beijing, China. The study was approved by the ethics committee of the Beijing Tongren Hospital, Capital Medical University (approval number: TRECKY2017-034) and registered at chictr.org.cn (registry number: ChiCTR-INR-17013294, date of registration 08 November 2017), prior to patient recruitment. The study was conducted according to common standard guidelines for clinical trials (Declaration of Helsinki, and the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use and Good Clinical Practice (ICH-GCP) revised version, Somerset West, Republic of South Africa, 1996) . All patients involved in this study gave their informed consent.
Patients: Male patients were admitted to our clinic for flexible cystoscopy. All patients were over 18 years old. Exclusion criteria included any analgesic used within 24 hours of the study period, known urethral stricture, previous history of urethral dilation, acute urinary tract infection, indwelling urethral catheter, and existing urethral pain (including chronic pelvic inflammatory disease and interstitial cystitis) Patients, as well as those who are unable to cope with pain assessment due to mental disorders.
Randomization: Patients were screened by the chief physician of the outpatient clinic. Use a computer (Random Allocation Software, version 1.0.0) to build a random number table, then randomly divide patients into two groups. The randomisation was carried out by an independent researcher who was not involved in the subject-recruitment process. The sealed opaque envelopes were used to ensure concealed allocation. Intervention participants in the trial knew the patient's grouping, and information collectors did not know the patient's grouping.
Design: We performed a prospective, randomized, controlled trial designed to compare pain scores between patients in experimental- and controls groups. Patients in the test group urinated during flexible cystoscopy. Patients in the control group received no instructions during the procedure. During examination, 10mls of 2% lidocaine gel was injected into the urethra and the penis was clamped for 10 minutes. A flexible cystoscope was passed through the urethra into the bladder for examination. All cystoscopies were performed by an experienced urologist. Flexible cystoscopy instruments included digital camera (Olympus OTV-S7), color video monitor (Olympus OEV-191H) and 16F flexible cystoscope (Olympus CYF-5A).
Intervention: The patient was taken supine position during cystoscopy. Routine disinfection. During examination, 10mls of 2% lidocaine gel was injected into the urethra and the penis was clamped for 10 minutes. The procedure of the control group was as follows: the examiner lifted the penis with his left hand, inserted the front end of the flexible cystoscope into the urethra with the help of his left thumb and index finger, and held the mirror with his right hand. The thumb controlled the adjusting lever. With the help of water flow, the examiner observed the urethral side entry mirror under video surveillance. Stay 1-2 seconds when seeing the external urethral sphincter and entered the bladder under direct vision. In the experimental group, the examiner lifts the penis with his left hand, inserts the front end of the flexible cystoscope into the urethra with the help of his left thumb and index finger, holds the mirror with his right hand, and controls the control lever with his thumb. With the help of water flow, the examiner observed the urethral side entry mirror under video surveillance. Stay for 1-2 seconds when seeing the external urethral sphincter and ask the patient to urinate. Then entered the bladder under direct vision.
Assessment: Patient histories were collected prior to operation. During cystoscopy, an experienced urologist nurse recorded the pain score according to the patient's assessment before aesthesia gel perfusion (baseline), anaesthetized gel perfusion, cystoscopy insertion into the urethra, and 15minutes post-examination analysis. Patients were asked to cross a line in a 10 cm region with 0 at one end of the transverse line indicating no pain; and 10 at the other end indicating a sharp intense pain.
Collection of co-variate data: Before the experiment, researchers collected general information about patients, including age, height, weight, and underlying diseases.
Sample size calculation: We used the result of Taghizadeh as the pain score of our control group, 2.82±1.2VAS . A minimal clinically important difference according to Todd was1.3 VAS . Given the effect size of Cohen’s d = 0.615, and a two-sided 5% level t-test with a statistical power of 1-β = 80%, 43 patients would be needed to detect this group difference. We planned to include 96 patients in this trial (n = 48 per group); recognizing a potential loss of analytical power due to patient withdrawal from 10%.
Data analyses: SPSS20.0 software was used for all data analysis. Data are expressed as mean ± standard deviation (SD), median and interquartile range (IQR) for variables that do not follow a normal distribution, or frequencies for categorical data. Normally distributed continuous variables were compared between the two groups using a two-sided t-test, with chi-square tests for categorical variables and with non-parametric Wilcoxon test for not normally distributed continuous variables. A p-value less than 0.05 was considered to be statistically significant.