Effect of radical prostatectomy on involuntary pelvic floor muscle contraction

Radical prostatectomy may cause stress urinary incontinence (SUI). We compared continent and incontinent men after radical prostatectomy, in regard to the change of the temporal pattern of pelvic floor activation during cough.

Twenty-two patients were included in this prospective, multicentric study. All patients gave their informed consent. Simultaneous recordings of electromyographic activity of external anal sphincter (EAS EMG) and external intercostal muscle (EIC EMG) during cough were performed with a pair of pregelled surface electrodes. Cough effort caused an involuntary pelvic contraction. Intercostal muscles recording was chosen because they are one of the muscular components of cough initiation with diaphragm muscle. Twenty-four-hour pad-weighing test was used to quantify urinary incontinence. The primary endpoint was the latency between the onset of EIC EMG and EAS EMG (RT3), during a cough effort. We also measured the contraction time, the maximum EAS EMG activity, and the area under the curve.

All the patients were analyzed: 12 continent and 10 with SUI. The median age was 66 years old. Both groups were similar except in term of follow-up. Median latency was increased by -1.7 ms (-47.9; +34.2) to 55.8 ms (+47.5; +80) in patients with SUI (P = 0.0033; Table 2). The duration of the contraction, the maximum EAS EMG activity and the area under the curve were not different.

The latency between the onset of EIC EMG and EAS EMG is increased in patients with SUI after radical prostatectomy. It may be one of the reasons for SUI in these patients.