Urinary incontinence (UI) is a frequent complication of radical robot-assisted prostatectomy (RARP) that reduces patients' quality of life. An effective method of instrumental diagnosis of UI, allowing successful planning of therapeutic strategies, differentiating the type of urinary incontinence, is a comprehensive urodynamic study (UDS). A large number of studies are devoted to the UDS in women; however, given the differences in UI etiology and pelvic muscle anatomy, a different approach may be necessary to diagnose UI in men after RARP.
According to Deffieux et al [1], an increase in bladder capacity may increase pelvic floor muscle tone. However, Huckabay et al [2] showed that urethral sphincter deficiency is best defined by low abdominal pressure threshold testing (ALPP) values, and higher ALPP values, may be accompanied by voluntary or involuntary contractions of the pelvic transverse band musculature. The concept of increased pelvic floor activity during coughing was confirmed by H.Luginbuehl et al [3].  Currently, there are few data on the relationship between bladder capacity and pelvic floor muscle activity during ALPP in men. Objective: To assess pelvic floor muscle activity using electromyography (EMG), at different bladder volumes, and their influence on ALPP results.

Prospectively UDS evaluated there were 15 patients, in 2020. Inclusion criteria: complaints of stress UI (SUI) of mild (1-2 pads) or moderate severity (2-3 pads per day), localized form of prostate cancer. Exclusion criteria: history of pelvic hormone therapy, stenosis of the vesico-urethral anastomosis, previous surgical interventions on the prostate, neurogenic urinary disorders. The UDS technique followed the good practice of the International Continence Society (ICS), a Laborie MMS Solar Uro urodynamic system was used, measurements were performed by water-perfusion method, mean filling rate 30 ml/min, Timman Ch8 type catheter, for recording the electromyographic potential of pelvic floor muscles (EMG) we used the pelvic floor surface electrodes, which were placed perianally at 3 and 9 o'clock; ALPP was performed on a second pattern to exclude obstructive gel effect on the catheter. ALPP was performed starting with a 50 mL capacity, followed by intermittent increases of 50 mL, until maximum cystometric capacity was reached.

Number of 15 patients, including Group I- 6 (40%) patients with mild SUI (1-2 pads per day) and Group II- 9 (60%) patients with moderate SUI (2-3 pads per day). The age of the patients under study was 64±7 years. The mean resting EMG value was 8±5uV. As bladder capacity increased, there was a 4±2 uV increase in pelvic floor bioelectrical activity from baseline values. Mean Pabd values in the ALPP test were 73±28 cmH2O. Overflow urinary incontinence was not detected in patients in either group. ALPP results at 200 ml capacity test "positive" Group I=1 (16%), Group II=6 (67%);  ALPP results at 100 ml capacity test "positive" Group I=4 (67%), Group II=8 (89%).
The ALPP test was "negative" at 100 mL capacity in 3 patients, including 2 patients in group I and 1 patient in group II. To exclude the obstructive effect of the catheter, the above patients were repeatedly performed the ALPP test after removal of the catheter, and a "positive" ALPP result was obtained.

According to the findings, patients with mild to moderate SUI can get a significant diagnostic benefit when performing ALPP with a bladder capacity of 100 ml.  At this threshold value, we did not detect a reflex increase in pelvic muscle tone in response to an increase in cystometric capacity. Figure 1 demonstrates an increase in pelvic floor muscle tone (EMG) in response to increased cystometric capacity and during ALPP.  The results of our study improve the accuracy of UDS ALPP in the diagnosis of SUI after RARP.

The main purpose of the UDS is to reproduce symptoms, particularly urinary incontinence after RARP. The ALPP test at a cystometric capacity of 100 ml increases the value of the UDS in the diagnosis of urethral sphincter insufficiency.

Deffieux X, Hubeaux K, Porcher R, Ismael SS, Raibaut P, Amarenco G. Pelvic floor muscle activity during coughing: altered pattern in women with stress urinary incontinence. Urology. 2007 Sep;70(3):443-7; discussion 447-8. doi: 10.1016/j.urology.2007.03.084. PMID: 17905093
Huckabay C, Twiss C, Berger A, Nitti VW. A urodynamics protocol to optimally assess men with post-prostatectomy incontinence. Neurourol Urodyn. 2005;24(7):622-6. doi: 10.1002/nau.20182. PMID: 16208638
Luginbuehl H, Baeyens JP, Kuhn A, Christen R, Oberli B, Eichelberger P, Radlinger L. Pelvic floor muscle reflex activity during coughing - an exploratory and reliability study. Ann Phys Rehabil Med. 2016 Dec;59(5-6):302-307. doi: 10.1016/j.rehab.2016.04.005. Epub 2016 Jun 2. PMID: 27265846