Date Published: January 31, 2016
Publisher: Hindawi Publishing Corporation
Author(s): Peter Rehder, Nina M. Staudacher, Joerg Schachtner, Maria E. Berger, Florian Schillfahrt, Verena Hauser, Raphael Mueller, Viktor Skradski, Wolfgang Horninger, Bernhard Glodny.
The proximal urethral bulb in men is enlarged, surrounds the bulbous urethra, and extends dorsally towards the perineum. During intercourse engorgement takes place due to increased blood flow through the corpus spongiosum. Antegrade ejaculation is facilitated by contraction of the bulbospongiosus muscles during climax. Micturition during sexual stimulation is functionally inhibited. Supporting the bulb may indirectly facilitate continence in a certain subset of patients with postprostatectomy incontinence. During physical activity with increased abdominal pressure, reflex contraction of the pelvic floor muscles as well as the bulbospongiosus muscles occurs to support sphincter function and limit urinary incontinence. Operations to the prostate may weaken urinary sphincter function. It is hypothesized that the distal urinary sphincter may be supported indirectly by placing a hammock underneath the urethral bulb. During moments of physical stress the “cushion” of blood within the supported corpus spongiosum helps to increase the zone of coaptation within the sphincteric (membranous) urethra. This may lead to urinary continence in patients treated by a transobturator repositioning sling in patients with postprostatectomy incontinence. This paper describes the possible role of the urethral bulb in male urinary continence, including its function after retroluminal sling placement (AdVance, AdVance XP® Male Sling System, Minnetonka, USA).
Postprostatectomy urinary incontinence still remains a significant problem in 2015. Of patients suffering from postprostatectomy urinary incontinence (PPI) roughly two-thirds have mild to moderate and one-third have severe urinary incontinence . Worldwide about 200 million people suffer from urinary incontinence of all causes . The incidence of urinary incontinence after prostate surgery (transurethral resection, simple open prostatectomy, and radical prostatectomy) varies between 1 and 5% . Surgery to the prostate may lead to incontinence rates of up to 77% depending on definition and time after surgery . Only a small proportion of patients with PPI are being treated with surgery. No randomized controlled studies exist comparing various operative techniques to treat male urinary incontinence. Recently a review paper has been published comparing different devices including the artificial urinary sphincter (AUS) AMS 800, Argus system (Promedon SA; Cordoba, Argentina), suburethral I-STOP TOMS (CL Medical), AdVance® Male Sling System (American Medical Systems, Minnesota, MN, USA), two-balloon ProACT™ (Medtronic, USA), ATOMS® device (AMI, Vienna, Austria), ZSI 375 artificial urinary sphincter (Zephyr Surgical Implants, Geneva, Switzerland), novel remotely controlled, artificial urinary sphincter, Virtue quadratic sling (Coloplast, Humlebaek, Denmark), and the periurethral constrictor (Silimed) . It was argued that all newer devices should be compared to the reported gold standard: the AUS AMS 800. This argument is based on the principle that the treatment of PPI functions on grounds of compression to the urethra and thus obstruction within the urethral lumen. The “functional” transobturator retroluminal repositioning sling supports sphincter function and does not compress to obstruct the urethral lumen. It functions as a dynamic hammock during moments of increased abdominal pressure [6–15]. The dilemma is that the mechanism of action of the “functional” sling is different to purely compressive slings or devices. A direct comparison is thus not possible, because compression versus support is like apples versus pears.
A short excursion is undertaken to describe the functional anatomy relevant to the urethral bulb, postprostatectomy incontinence (PPI), and diagnosis and workup of PPI and male urethral sling surgery. The current understanding of male urethral sphincter remains an area of constant debate. A PubMed and Google Scholar search was done to include some relevant publications in the discussion. A short description is included to demonstrate the surgery involved when placing a transobturator retroluminal repositioning sling. Images using magnetic resonance and perineal ultrasound illustrate final sling position and intact urethral bulb blood supply.
A healthy urethral bulb/corpus spongiosum is of critical importance for the successful outcome of the transobturator retroluminal repositioning sling. Radiotherapy reduces the blood supply to the corpus spongiosum with poor results after sling placement [27–33]. Direct injury to the urethral bulb during sling surgery may also cause damage with resultant scarring and a poorer outcome after sling placement. As shown in Figure 10 the sling clearly lies dorsally to the urethral wall, relying on healthy blood filled spongiosum tissue to help coapt the urethral lumen during increased abdominal pressure. The pressure may thus be transmitted from the retroluminal sling functioning as a dynamic hammock to help treat stress urinary incontinence.
The proximal male urethral bulb is an integrated part of the urinary continence mechanism, especially during increased physical activity. Sphincter function may be supported by dynamic compression, when it is compromised after prostatic surgery. Such dynamic compression is achieved by placing a transobturator sling to proximally indent the corpus spongiosum. A hammock now exists with a cushion of blood filled spongiosum tissue, to dynamically lengthen the zone of coaptation in the distal sphincteric urethra during moments of increased physical activity.
The male urethral bulb most probably has an important additional function to maintain urinary continence during physical exercise also in normal men. Contraction of the bulbospongiosus muscles indirectly leads to coaptation of the distal membranous and proximal bulbous urethra. An increased coaptation of the urethral lumen distal to the membranous urethra ensures continence by lengthening the coaptive zone, starting at the bladder neck, throughout the prostatic urethra to the membranous urethra including the pars nuda  onto the proximal bulbous urethra.