Bulbomembranous urethroplasty: External sphincter-sparing approach

Bulbomembranous urethral strictures (BMUS) after surgery for BPH are challenging, as the internal sphincter located at the bladder neck has been removed by prostatectomy, and urinary continence now depends on the function of the external sphincter, which is located just at the site of the stricture. Consequently, any attempt at stricture reconstruction may jeopardize continence. For this reason, in most cases these patients are only offered conservative management, such as dilation or internal urethrotomy. Unfortunately, these options are seldom curative and the stricture becomes a chronic condition.  

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Interestingly, anatomic studies have shown that the external sphincter (rhabdosphincter) is separated from the membranous urethra by a sheath of connective tissue, a feature that has previously gone unnoticed (BJU Int 2008; 102:1448-51). Our group developed a novel technique for intra-sphincteric bulbo-prostatic anastomosis (ISBPA) using this anatomic feature. Through a gentle meticulous dissection of this connective tissue sheath, we were able to create a surgical plane that allowed us to separate the muscle from the urethral wall, thus enabling us to resect the stricture and perform a primary anastomosis without disturbing the external sphincter function.

This article describes the surgical steps in this new technique and our promising preliminary results. 

Next: Surgical technique

Surgical technique

Patients with BMUS after transurethral resection of the prostate (TURP) or open simple prostatectomy (OSP), who failed conservative management with dilation and/or internal urethrotomy, were reconstructed with an ISBPA with preservation of the fibers of the external sphincter.

The bulbar urethra is approached through a standard vertical perineal incision with splitting of the bulbospongiosus muscle in the midline. The bulbar urethra is then separated from the underlying corpus cavernosum and elevated with two vessel loops. This surgery is highly facilitated with the aid of the Scott (Lone Star) retractor (CooperSurgical, Inc., Trumbull, CT). Opening of the perineal membrane and splitting the intercrural space in the midline provides access to the dorsal aspect of the bulbomembranous junction.

The bulb is then mobilized from one side only, without detachment from the perineal body. After bulbomembranous junction exposure, the bulbar vessels are retracted posteriorly with another vessel loop as described by Jordan et al (J Urol 2007; 177:1799-802) (figure 1).

Finally, the membranous urethra is secured with a fourth vessel loop. The sheath of the membranous urethra is now opened circumferentially at the bulbomembranous junction, carefully reflecting the circular muscle fibers of the external sphincter until exposure of the urethral wall is obtained and the connecting tissue plane is identified (figure 2). Gentle blunt proximal dissection along this plane allows separating the muscle away from the urethra up to the prostatic apex, where healthy urethra is found to perform the anastomosis (figures 3 and 4). The anastomosis is usually performed with six 5-0 monofilament absorbable sutures (poliglecaprone [Monocryl]) incorporating only the urethral wall-but not the muscle-at the prostatomembranous junction. Both urethral ends should be free of fibrosis, exhibit a healthy-looking mucosa, and accept a bougie 28F.

Stitches are placed at the 12, 2, 4, 6, 8, and 10 o’clock positions. Since the bulb has not been detached, the sutures at 2 and 4 o’clock need to be transferred counter-laterally to complete and tie the parachute (figure 5). After knot tying, the ring of sphincter muscle is anchored to the anastomosis site with three or four interrupted sutures (figure 6). A 16F silicone Foley catheter is left for 2 weeks and is removed if pericatheter urethrography shows absence of extravasation.

Patients are followed clinically and incontinence evaluated according to the number of daily pads. Patients reporting partial continence are scheduled for perineal physiotherapy.

Next: Results

Results

Twenty-three patients with BMUS were operated on between January 2010 and October 2015, 14 after TURP, and nine after OSP. All had a membranous or bulbomembranous stricture; bladder neck contractions were excluded. Mean age was 68 years (range, 57-81 years). All but four patients were treated with repeated dilations or internal urethrotomy, seven with a suprapubic tube, and five had a totally obliterative stenosis. Mean length of stricture was 3 cm (range, 1-4.5 cm), and mean time from surgery to reconstruction was 30 months (range, 2-153 months).

At a mean follow-up of 34 months (range, 1-68 months), all patients were voiding stricture free, without recurrence; 19 of 23 patients were completely dry or using only one security pad (83% success). There were three Clavien I complications (two perineal hematomas and one delirium) and one Clavien III complication (early catheter dislodgement requiring surgical repositioning).

Next: Discussion

Discussion

Development of urethral strictures after surgery for BPH is a highly undesirable complication. It has been traditionally linked to operative trauma at the time of digital enucleation of the prostate or caused by the resectoscope, but it can also be catheter related. These strictures can be located anywhere along the urethra, but the most feared are those affecting the posterior urethra (bulbomembranous junction and/or membranous urethra). Since the bladder neck has been removed by BPH surgery, the internal sphincter mechanism is no longer present; therefore urinary continence relies on the external sphincter (or rhabdosphincter).

Unfortunately, this sphincter is located right at the stricture site, so any attempt at excision and primary anastomosis of the stricture may damage the sphincter, rendering the patient incontinent. Most reconstructed patients would eventually need an artificial sphincter.

In 2008, Dalpiaz et al performed anatomic dissection studies in cadaveric pelvises and described the existence of a delicate sheath of connective tissue between the wall of the membranous urethra and the surrounding circular fibers of the external sphincter. They postulated that this sheath could be used as a surgical plane to separate the urethral wall from the sphincter, proving the basis for sphincter-sparing surgery in this area (BJU Int 2008; 102:1448-51).

We applied this concept in patients with recurrent membranous or bulbomembranous strictures who failed conservative management. We have found that this sheath is readily identifiable and provides an ideal surgical plane to isolate the urethral wall, allowing the reparation of the stricture without damaging the sphincter. There were some cases in which scar extended to and involved sphincter. Of note, all cases are not the same; in some patients, this surgical plane was easier to find and develop than in others.

Next: An evolving technique

However, we still cannot correlate these operative findings with the eventual outcome in terms of postoperative incontinence. This is an evolving technique and the series is still too small. We are now looking for prognostic factors to identify those at higher risk of postoperative incontinence.

We believe surgical exposure of the bulbomembranous junction is crucial, and we use four vessel loops as described. Furthermore, we do not detach the bulb from the perineal body as is normally done to approach the posterior urethra; lateral retraction with vessel loops provides enough space for dissection and stricture reconstruction, no different from the standard transecting approach. Avoiding detachment of the bulb is less invasive, allows better stabilization of the membranous urethra during sphincter stripping, and preserves bulbar artery perfusion, which may be important should an artificial sphincter be required in the future.

Caveats. Although we have been able to solve the stricture in all cases, we are aware that more experience is needed to refine the results, since incontinence can still occur in some cases. The series is too small to identify the best candidates. For example, we cannot know if strictures after TURP or after OSP are the same, nor can we know if strictures (“stenosis”) at the bulbomembranous junction are the same as strictures involving the whole membranous urethra, to name just two variables. However, the anatomic principles behind our technique and these preliminary results are sound, and we believe it is a suitable alternative for these unfortunate patients.

Conclusion

Excision and bulbo-prostatic anastomosis with external sphincter sparing for BMUS after BPH surgery is feasible and safe. Our technique preserves continence in most patients, and to our knowledge it has not been described before.

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