Free tubularised vesical mucosa graft for congenital stenosis of the urethra in children

25 février 2015

Auteurs : S. Mouttalib, O. Bouali, O. Abbo, J. Moscovici, P. Galinier
Référence : Prog Urol, 2015, 2, 25, 109-114




 




Introduction


Urethral strictures in children are often part of complex urethral problems related to different rare congenital anomalies and remain a challenge to the pediatric urologist. Severe strictures may threaten renal function, and require early repair in young children. Multiple techniques have been described for their repair. We aimed to assess the effectiveness of staged repair with use of a free tubularised bladder mucosal graft and prior vesicostomy. To our knowledge, this technique of reconstruction using a tubularised bladder mucosal graft has not been described yet in children [1, 2, 3].


Patients and results


Case 1


First case has previously been reported as a case report [4]. A full-term newborn was referred to our department for a complex urogenital anomaly associated with a high anorectal malformation (ARM). The child had a large midshaft penile fistula, stenosis of the bulbar urethra, bifid scrotum, penoscrotal transposition and absence of an anus, along with normal glanular urethra, apical meatus, and normally descended testes (Figure 1a). Renal function was normal. No anomaly was found in the hormonal work-up.


Figure 1
Figure 1. 

a: wide urethral fistula and bifid scrotum in patient 1; b: large diverticular bladder and stenosis of the bulbar urethra (arrow) in patient 1.




Abdominal ultrasonography showed a large diverticular bladder associated with a dilatation of the superior urinary tract. Radiographs (head-down view) showed a high ARM. As there was no spontaneous micturition, and given the impossibility of catheterising the child, a suprapubic catheter was inserted. Antegrade cystourethrogram showed a large diverticular bladder and a near total stenosis of the membranous urethra above the midshaft penile fistula (Figure 1b). The stenosis was more than 1 centimeter long.


Initial operative procedures included colostomy and cutaneous tubeless vesicostomy. At seven months, the child underwent posterior sagittal anorectoplasty (Peña procedure). No rectourethral fistula was found, which is unusual in high ARM.


At the age of 17 months, urethroplasty was performed on the membranous urethral stenosis. A free bladder mucosal graft was used for the treatment of the stenosis. The vesicostomy was closed at the same time. Two months later, cystourethroscopy showed that the reconstructed urethra was permeable.


At the age of 24 months, the penile fistula was closed using a Duplay procedure ensuring that the reconstructed urethra was preserved. Correction of the scrotal transposition was performed at once.


After eight years of follow-up, the cosmetic and functional results are satisfying (Figure 2, Figure 3) and the child is continent day and night.


Figure 2
Figure 2. 

End of treatment: satisfying cosmetic result in patient 1.




Figure 3
Figure 3. 

End of treatment: satisfying functional result in patient 1.




Case 2


The second child was a full-term male newborn admitted for a complete patent urethral duplication with two meati: an apical meatus and an anterior penile hypospadiac meatus. Antenatal bilateral ureterohydronephrosis had been detected on fetal ultrasound scans. Unusually, it was not possible to catheterise the ventral hypospadiac urethra whereas the apical urethra showed a good caliber (Figure 4a).


Figure 4
Figure 4. 

a: urethral duplication and congenital stenosis at the bulbar junction of the two duplicated urethras (patient 2). The apical urethra showed a good calibre whereas it was not possible to catheterise the ventral hypospadiac urethra; b: antegrade cystourethrogram before surgery (patient 2): bladder (B) with a large diverticulum (D) and vesicoureteral reflux (R). Stenosis on the apical urethra at the bulbar junction of the two duplicated urethras (arrow).




The external genital organs were normal. The left kidney was not functioning while the right kidney showed compensatory hypertrophy. Abdominal ultrasonography showed bilateral ureterohydronephrosis and bladder wall thickening.


Given the absence of spontaneous micturition and impossibility to catheterise the child, a suprapubic catheter was initially introduced. Antegrade cystourethrogram showed a complete patent urethral duplication with two meati. The hypospadiac channel arose from the first meatus and coursed independently to the second meatus, realising a type IIA2 urethral duplication according to the classification of Effmann et al. [5]. There was a stenosis on the apical urethra, at the bulbar junction of the two duplicated urethras (Figure 4b). This stenosis was 0.5cm long.


A cutaneous tubeless vesicostomy was then performed during the neonatal period. At the age of two years, urethral reconstruction was performed (Figure 5) with a free bladder mucosal graft that was tubularised. The vesicostomy was closed in two planes and the bladder was drained with a suprapubic catheter for 21 days. Six months later, cystourethroscopy and permictional urethrocystography (Figure 6) showed that the reconstructed urethra was permeable.


Figure 5
Figure 5. 

Exposure of the congenital stenosis at the bulbar junction of the two duplicated urethras (patient 2).




Figure 6
Figure 6. 

Permictional urethrocystography after reconstruction showing a permeable reconstruction in patient 2. Bladder (B), diverticulum (D), no vesicoureteral reflux, permeable reconstructed urethra using a free tubularised vesical mucosa graft.




After three years of follow-up, functional voiding results are satisfying and renal function is normal.


Technique


With the patient in lithotomy position, the bulbocavernous muscles were divided through a midline incision on the raphe, exposing the bulbar urethra, which was dissected from the corpora cavernosa, and a circumferential excision of the strictured urethra was performed.


The bladder was approached through a Pfannenstiel transverse suprapubic incision and a Dennis-Brown retractor allowed adequate exposure of the bladder. The detrusor was carefully incised and peeled away from the underlying bladder mucosa (Figure 7). A large section of bladder mucosa was exposed, marked with a surgical skin marker, and excised with the help of stay sutures. The bladder was closed in two planes and drained with a suprapubic catheter in addition to the vesicostomy. A Redon drain was left into Retzius' space for five days.


Figure 7
Figure 7. 

Bladder mucosa harvesting. Detrusor is carefully incised and peeled away from the underlying bladder mucosa, exposing a large section of bladder mucosa, which is then excised.




The harvested graft was prepared removing all muscle tissues, leaving only mucosa remaining. The mucosal graft was repeatedly moistened with saline solution, and loosely rolled on a 12 F silicone catheter (Figure 8), with its inner mucosal surface placed against the drain, then tubularised over the drain using a 7-0 PDS running suture with interrupted sutures at both ends.


Figure 8
Figure 8. 

Tubularisation of the mucosal graft, which is loosely rolled on a silicone catheter, and tubularised using a running suture with interrupted sutures at both ends.




The ends of the remaining native urethra and the graft were spatulated to ensure wide elliptic anastomosis. The tubularised graft was placed with its longitudinal suture towards the corpora cavernosa. The distal and proximal ends of the graft were sutured to the native urethra using interrupted 6-0 and 7-0 PDS sutures. The corpus spongiosum, the perineal superficial fascia, the perineal fat, and the skin were closed over the graft with interrupted absorbable sutures. A longitudinally opened silicone drain (10 F) was placed through the entire urethra from the urethral meatus to the proximal urethra. This drain was extended only a few millimeters above the proximal anastomosis but not into the bladder to keep the anastomosis "dry". Urines were only drained through the suprapubic catheter. The silicone drain was left in place for three weeks.


The postoperative course was unremarkable. Both patients were discharged home 21 days after surgery.


Discussion


A wide variety of surgical treatment options are described for anterior urethral strictures in children including dilatation, urethrotomy, and different reconstructive techniques as excision and primary anastomosis [6], buccal or bladder mucosa onlay graft, penile skin flap.


Urethral strictures in children often have an acquired aetiology, mostly as the consequence of hypospadias surgical repair, although the long-term function of these reconstructions is poorly defined. For children with congenital strictures, the optimal timing and method of reconstruction are even poorly defined [1, 7]. For these reasons, there is no standardised approach to repair congenital urethral strictures.


Both our patients had long strictures as a part of a complex urethral malformation, excluding dilatation and urethrotomy. Excision and primary anastomosis were not appropriate because of the risk of developing chordee in growing patients.


Within substitution urethroplasties, limited small case series, mostly conducted in traumatic strictures, have shown that patch grafts have a lower restricture rate than tubularised grafts in this inflammatory context [8, 9]. The anatomic configuration in our patients would not have allowed us to use a patch graft, as the stricture was a part of a congenital complex urethral malformation with no viable urethral plate.


Buccal and bladder mucosa grafts have both been used in bulbar urethroplasty, and there is no absolute superiority of one over the other [10]. Humby [11] described urethral substitution using buccal mucosa in 1941, and buccal mucosa grafts became popular in the 1990s. Some authors consider that buccal mucosa grafts are an ideal substitute for the urethra, given its resistance to infection and compatibility with a wet environment [12]. Others find many disadvantages in these grafts, including postoperative pain, complications in the donor site [13], and unpredictable take of the graft, which can lead to scarring and fibrosis [14].


Bladder mucosa is an accessible material for urethroplasty, and provides long grafts. It was first been used for reconstruction of urethra by Memmelaar in 1947 [15]. As an uroepithelium, bladder mucosa is similar to the urethral mucosa and is not altered by the exposure to urine. It has a tendency to shrink [16] and to proliferate when exposed to irritative factors such as air [17]. In tubularised bladder mucosa grafts used for hypospadias repair, the most common complications are meatal stenosis and prolapse [18], which does not apply in a bulbar reconstruction, as the bladder mucosa has no exposure to air. As bladder mucosa's immunohistological properties are the most similar to those of the urethral tissue [19], our technique may minimise the risks of stenosis associated with other tissues.


Harvesting bladder mucosa could be more difficult in patients with previous bladder surgery; in our cases, there was no visible bladder wall inflammation and the previous vesicostomy did not make the graft harvesting more difficult.


The only paper that we found mentioning tubularised bladder mucosa grafts in strictures (n =3) was performed in adult patients with traumatic complex urethral strictures over 8cm in length. It showed limited outcome [20]. In our two children, the postoperative evolution was successful with satisfying cosmetic and functional results in the two cases.


In conclusion, we report successful long-term graft function following free tubularised bladder mucosa graft reconstruction for congenital urethral strictures. We found excellent functional results out to at least 3 years. A longer follow-up on a larger series of patients is necessary to confirm our satisfactory preliminary reports for this technique.


Disclosure of interest


The authors declare that they have no conflicts of interest concerning this article.



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