Reliability of a new method for assessing urethral compression following midurethral tape procedures using four-dimensional ultrasound

Objectives To evaluate the intra- and interobserver reliability of a new method of assessing resting and dynamic urethral compression after midurethral tape procedures using three- and four-dimensional (3D and 4D) ultrasound. Methods Thirty-one women who had undergone transobturator midurethral tape procedures at Cathay General Hospital were enrolled in the study and 4D ultrasound was performed pre- and postoperatively. Preoperative ultrasound assessment included measurement of the urethral central echolucent area (UCEA) in the axial plane. Postoperative ultrasound assessment included measurement of the tape-urethral distance (TUD) in the sagittal plane as well as UCEA and tape angle in the axial plane (ATA). The TUD was measured at the upper end (TUDu), central point (TUDc) and lower end (TUDl) of the tape. All pre- and postoperative ultrasound assessments were performed in women at rest, on maximum straining and during strong coughing. 4D ultrasound volume datasets were stored digitally and analyzed offline by two independent investigators blinded to clinical data and to each others' measurements. Intra- and interobserver reliability were evaluated using the intraclass correlation coefficient (ICC). Results There were significant reductions in TUDc, TUDl and UCEA during increased intra-abdominal pressure. ICC values for the measurement of TUD at rest, on straining and during coughing demonstrated very good reliability. ICC values for the pre- and postoperative measurement of UCEA at rest, on straining and during coughing demonstrated good to very good reliability. ICC values for the measurement of ATA at rest, on straining and during coughing demonstrated fair to good reliability. Conclusions 4D ultrasound can be used to obtain measurements with good reliability in the assessment of urethral compression.