Comments on "Association Between Urinary Stress Incontinence and Levator Avulsion Detected by 3D Transperineal Ultrasound".

It is a very interesting report about the association between stress urinary incontinence and levator avulsion [1]. I congratulate the authors for performing such a large sample study on stress urinary incontinence (SUI) and presenting a new finding that the unilateral levator ani muscle avulsion correlated with SUI. However, I have several queries regarding the study. First, the terminology “USI” refers specifically to “urodynamic stress incontinence,” i. e., stress urinary incontinence (SUI) diagnosed by urodynamic testing. “USI” was defined as involuntary urine leakage with stress in the absence of detrusor contraction during filling cystometry [2]. It looks like the term “USI” in this study indicated the symptoms of SUI, which is the involuntary leakage of urine following physical activity, such as coughing, sneezing, or laughing [3]. Second, the methodology of the threedimensional transperineal ultrasound used in this study was incorrect. The authors did not perform the repeatability test for the diagnostic methods of levator ani muscle avulsion. However, the legends of the diagnostic image were incorrect. The legends of Fig. 3 and Fig. 4 were switched. Fig. 3 showed the measurement of the hiatal area, while Fig. 4 showed the LUG measurement. The legend of Fig. 5 was wrong. The picture on the left showed a partial avulsion on the right lateral levator ani muscle. The picture on the right showed a levator ani muscle avulsion on the left sideway. The explanation in Fig. 6 was wrong. The image showed a full avulsion on the right lateral and a partial avulsion on the left lateral. Third, there was an obvious sample selection bias in this study. Generally, levator ani muscle avulsion was correlated to severe pelvic organ prolapse. The incidence of levator ani muscle avulsion in Chinese women with pelvic organ prolapse was 38.9 % [4], and it was 19.0 % in primiparous women at 8 weeks after delivery [5]. The prevalence of levator ani muscle avulsion in women without pelvic organ prolapse (204/593, 34.4 %) in this study was much higher than in other studies on Chinese women. Furthermore, the prevalence of SUI in this study was lower. Authors reported that “USI was found in 7.71% (30/389) in the no-avulsion group, 10.71 % (3/28) in the B-avulsion group, 20.00 % (16/80) in the R-avulsion group, and 18.75 % (18/96) in the L-avulsion group.” However, Zhu Lan, a famous pelvic floor expert in Peking Union Medical College Hospital, reported that the prevalence of female urinary incontinence is high (38.5 %) in Beijing. Among the different types of urinary incontinence, SUI was the most prevalent (22.9 %) [6]. Chan SS reported that the prevalence of SUI was 25.9 % twelve months after delivery [7]. In summary, the diagnostic methodology in this study was incorrect. The study data was not credible. The conclusion that “unilateral levator avulsion may be a risk factor for urinary stress incontinence” is debatable.