Neurourology and Urodynamics. 2019;1-7. wileyonlinelibrary.com/journal/nau © 2019 Wiley Periodicals, Inc. | 1 Received: 5 October 2018 | Accepted: 29 May 2019 DOI: 10.1002/nau.24080 ORIGINAL CLINICAL ARTICLE Urethral diverticula in women are associated with increased urethra‐sphincter complex volumes: A potential role for high‐tone nonrelaxing sphincter in their etiology? Bashir M. B. Mukhtar 1 | Eskinder Solomon 2 | Sahar Naaseri 3 | Paul Aughwane 3 | Mahreen Pakzad 4 | Rizwan Hamid 4 | Jeremy L. Ockrim 4 | Tamsin J. Greenwell 4 1 Department of Urology, University Hospital of Wales, Cardiff, UK 2 Evelina London Children’s Hospital, St. Thomas’ Hospital, London, UK 3 Department of Radiology, UCLH at Westmoreland Street, London, UK 4 Department of Urology, UCLH at Westmoreland Street, London, UK Correspondence Tamsin Greenwell, Department of Urology, UCLH at Westmoreland Street, London W1G 9PH, UK. Email: Tamsin.greenwell@nhs.net Abstract Aims: Functional obstruction secondary to a high‐tone nonrelaxing sphincter (HTNRS) may lead to the formation of a proximal‐to‐mid‐urethral diverticulum (pmUD) in patients without a history of anatomical obstruction, vaginal delivery, vaginal and/or urethral surgery, or periurethral gland infection, that is, a functional pmUD (fpmUD). We used measurements of the urethra‐sphincter complex volume (USCv) as a proxy for the maximal urethral closure pressure to evaluate this potential etiological factor. Methods: We compared 17 consecutive women with fpmUD (mean age ± SD of 49.4 ± 13.2 years) with a control group consisting of 24 age‐matched women (mean age: 50.8 ± 11.2 years) with no previous urological symptoms having MRI for posthysterectomy vesicovaginal fistula, and in all 71 women (mean age: 48.1 ± 11.6 years) with classical urethral diverticulum (cpmUD) referred in the same time period. The urethra‐sphincter complex was measured using T2‐weighted MRI and OsiriX © was then used to determine the USCv. Results: The mean USCv of the fpmUD group was 10.01 ± 6.97 cm 3 . The mean USCv of the cpmUD was 5.19 ± 1.19 cm 3 and for the control group was 3.92 ± 1.60 cm 3 . There was a high statistically significant (P = .01) difference between the USCv in the fpmUD group and the USCv of both the cpmUD and the control groups. Conclusions: Women with fpmUD demonstrated USCv that were significantly higher than those in women with cpmUD and the control group. These findings suggest that high pressure in the proximal urethra during voiding secondary to a HTNRS may contribute to the formation of urethral diverticula. KEYWORDS high‐tone nonrelaxing sphincter, MRI volume, sphincter complex, urethral diverticulum 1 | INTRODUCTION Urethral diverticulum (UD) in women is uncommon, with an incidence of 0.02%‐6%, worldwide. 1,2 Symptomatic patients typically present between 30 to 60 years with a All work on this paper was performed at UCLH at Westmoreland Street, 16‐18 Westmoreland Street, London W1G 9PH, United Kingdom.