Decreased Urethral Volume Is Comparable to Funneling as a Predictor of Intrinsic Sphincter Deficiency

The aims of this study were to determine the association between x-ray funneling and ultrasound urethral sphincter complex measurements and to compare the reliability of funneling versus urethral volume measurement in the detection of intrinsic sphincter deficiency (ISD).

This was a retrospective analysis, which included 54 stress incontinent women dichotomized into those with (1) ISD and (2) no ISD. The presence of bladder neck funneling was diagnosed by fluoroscopic images obtained at the time of video-urodynamics testing. Measurements of the urethral sphincter complex were obtained from ultrasound volumes. Reliability measures were obtained for both funneling and urethral volume measurements.

Rhabdomyosphincter length and area were found to be smaller in patients with funneling compared with those with no funneling (P = 0.0161, P = 0.0359). The urethral volume was significantly smaller in the ISD versus no-ISD group (P = 0.0002). For those who had funneling, the ISD group had smaller urethral volume compared with the no-ISD group (P = 0.0019). For those who did not have funneling, the ISD group still had a smaller urethral volume compared with the no-ISD group (P = 0.0054). An ultrasound urethral volume of less than 3.5 cm had a sensitivity of 81% and a specificity of 64% for the presence of ISD, whereas x-ray funneling had a sensitivity of 76% and a specificity of 73%.

Smaller rhabdomyosphincter length and area on ultrasound are associated with x-ray funneling. Ultrasound urethral volume of 3.5 cm as a cutoff provides the same reliability as x-ray funneling for the diagnosis of ISD.