10 - Ultrasound imaging of the lower urinary tract and uterovaginal prolapse

Summary

Introduction

For many years, urogynaecologists and urologists have relied on cystometry and urethral function tests to evaluate the female lower urinary tract. However, with the improvements in ultrasound imaging techniques, this diagnostic modality has been increasingly used for the assessment of lower urinary tract dysfunction and pelvic floor disorders. Ultrasound has the advantage of being able to visualise fluid-filled structures without the need for contrast medium. It can also demonstrate soft tissue structures such as the kidney, bladder wall, urethral and anal sphincters and surrounding pelvic floor musculature. It also avoids ionising radiation and can be used safely and repeatedly in women of reproductive age. Most ultrasound equipment is transportable and readily available within a gynaecological department. Operating costs of ultrasound are low and the technique should be readily available in most urogynaecological units.

Ultrasound of the lower urinary tract and pelvis

The bony enclosure of the pelvis around the empty bladder and urethra limits the views obtained by ultrasound imaging. Use of the transabdominal, transvaginal, transrectal and transperineal approaches for ultrasound scanning allows for easy visualisation of different aspects of the lower urinary tract. Perineal and transabdominal probes are usually linear array transducers, while transvaginal and transrectal probes are either linear array or sector scanners. Linear array scanners have the disadvantage of being bulky and having low operating frequencies, whereas sector scanners are smaller, more expensive and operate at a higher frequency producing better image resolution. Higher ultrasound frequency provides better image resolution at the expense of decreased depth of penetration owing to increased attenuation.