We read with interest the recent article by Houwert et al on the analysis of risk factors for failure of retropubic and transobturator midurethral slings. One of their conclusions is that low maximal urethral closure pressure is a risk factor for failure for transobturator slings.

We compliment the authors on their rigorous trial design. We would, however, respectfully request clarification on a few points.

It is well known that urethral mobility is the most important prognostic factor that has an effect on the success of the midurethral sling procedure. On close observation of Table 1 there were 4 patients with no hypermobile urethra in each group, and 26 and 5 patients with maximal urethral closure pressure <20 cm H ₂ O in the retropubic and transobturator group, respectively. However, it is not clear if the 4 patients with intrinsic sphincteric deficiency who were not cured in the transobturator group, accounting for a failure rate of 80%, which is higher than that reported in recent literature, are the same patients with no hypermobile urethra. We believe that if this is the case it should be reported and their conclusion should probably be changed accordingly.