Study of the artefacts induced by linear array transvaginal ultrasound scanning in urodynamics

In patients with incontinence problems, endovaginal urodynamic ultrasonography is a technique which easily complements manometric examination by permitting a precise study of peri-urethral soft tissue. Use of a linear array probe under standardised conditions gives, at present, the best results. To validate the technique, it is, however, important to understand the artefacts it provokes. Thirty-four patients underwent urethral profilometry at rest and during effort with and without the ultrasonographic probe. In the patients studied, none of the classical urodynamic parameters were modified. However, in cases of narrow vaginas (distance between the arcuate ligament and the ultrasonographic probe less than 12 mm), a small increase in the maximum urethral closure pressure (5 cm H2O) could be observed. The angle between an intra-urethral cotton swab and the horizontal plane was measured at rest and during maximum coughing effort, both with and without the ultrasonographic probe. A significant reduction of the angle was observed at rest and during effort. However, since linear regression is particularly effective in modelling these two artefacts (R2 = 0.8 and 0.7), they can be considered as constants and are not bothersome in clinical practice. Abdominal ultrasound was used in 10 patients during the introduction of the endovaginal ultrasonographic probe to study its impact on the base of the bladder. A clear increase in the posterior urethro-vesical angle was observed, which was shown to be a function of the degree of probe insertion in the vagina. As this artefact was variable and could not be controlled, this angle should no longer be measured using this technique.(ABSTRACT TRUNCATED AT 250 WORDS)