Between January 2009 and January 2014, women with urodynamic stress incontinence (USI) scheduled for mid-urethral sling surgery in the urogynecological department of a tertiary referral center were recruited. A retrospective chart review was performed. This study received approval from the Institutional Review Board of Kaohsiung Medical University Hospital (ID:KMUHIRB-E(I)-20210275), by which relevant guidelines and regulations were followed accordingly. Informed consent was obtained from all participants before surgeries. The Q-tip test was performed via a cotton swab with the patient in a 45-degree reclining. After lubricated with 2% lidocaine jelly, the cotton swab was inserted with the tip over bladder neck. The angle changes from rest to maximal straining were obtained for 3 times, and the maximum of angle change was recorded. The TPUS was performed by two experienced urogynecologist according to KMUH-TPUS protocol. The Voluson General Electric Sonography, expert 730 type (GE, Healthcare Ultrasound, Zipf, Austria) Ultrasonography was used with 3.5 MHZ curved linear-array transducer placed between the major labia and underneath the external urethral orifice. The measurement was done on the midsagittal plane to obtain the image of pubic symphysis, urethra, and bladder in a view. Ultrasonic measurement of the overall rest-stress distance was define as the linear distance of bladder neck position change from resting status to maximal strain. The rest-stress distance was obtained for 3 times, and the maximum of distance was recorded. The primary outcome of this study was the correlation between the angle of Q-tip test and the overall rest-stress distance of bladder neck in TPUS. The secondary outcome was the optimal cut off value of the rest-stress distance to predict UH.