Inter-observer and Intra-observer Reproducibility for the Determination of Female Urethral Narrowing on Voiding Cystourethrogram: A Retrospective Study

Background The voiding cystourethrogram (VCUG) is used in women to evaluate the anatomy of the lower urinary tract. Once common for detecting reflux, urethral mobility, and diverticula, its use in adults has declined. However, VCUG remains valuable in urogynecology and reconstructive pelvic surgery (URPS) by identifying structural causes of recurrent urinary tract infections (RUTI), such as urethral pathology. Objective The main objective of this study is to evaluate the inter and intra-observer variability among radiologist interpretations of urethral caliber and narrowing on VCUG. Methods Following IRB approval, 83 VCUG cases performed on non-neurogenic women between 18 and 85 years old, and without prolapse >stage 2, were identified retrospectively from a tertiary care urology clinic between January and July 2023. All studies were performed in the upright sagittal oblique projection. Each image was independently reviewed by four abdominal fellowship-trained radiologists, who judged whether each urethra was narrow or not. If narrow, the rater noted severity (mild, moderate, severe) and location (proximal, mid, distal). The Shrout-Fleiss reliability statistic for a fixed set of raters (intra-class correlation (ICC): 3, k) was then calculated for the presence or absence of narrowing. Results In 50/83 (60%) of cases, all raters agreed on whether the urethra was narrow. Majority agreement (at least three of four raters) was present in 75/83 (90%) of cases. The ICC (3, k) was 0.79 for the reliability of the four scores. For the 61 cases rated as narrow by at least three of the four radiologists, the majority agreed on the degree of severity in 43/61 (70%; ICC = 0.89) of cases, and on location in 51/61 (84%; ICC = 0.43) of cases. Conclusion To our knowledge, this is the first study to assess the inter-reader reproducibility of urethral narrowing on standing VCUG in women with lower urinary tract symptomatology. A majority agreement was reached on urethral narrowing, including its location and severity. Correlating VCUG findings with clinical data will help establish a standardized radiologic definition of urethral narrowing.