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Buccal Mucosa: Good But Not Perfect
Buccal Mucosa: Good But Not Perfect IN 1995 Baskin and Duckett described the favorable histological properties of buccal mucosa as a graft material, and reported encouraging clinical results in hypospadias urethroplasty.1,2 However, deploying buccal mucosa in 1 stage for full circumference urethral substitutions was not without problems. Indeed years later Snodgrass polled pediatric surgeons at a national meeting and found that 50% reoperation rates were the norm for 1-stage buccal tubes. This finding should not be surprising given that the ventral soft tissues in the hypospadias penis do not lend good vascular or mechanical support for take of a free graft. Unlike the obligatory wet mucosa of the bladder, oral mucosa is able to withstand exposure to air and, thus, can be deployed in a similar manner to skin grafts. Thus, having already had excellent results using 2-stage skin grafts for full circumference urethral reconstruction in hypospadias,3 I started using buccal mucosa in a similar manner around 1992. Having a focused high volume throughput, my experience with staged buccal mucosa has been favorable. Preliminary audit data from 300, 2-stage buccal graft urethroplasties (a heterogeneous group of children and adults with various pathologies) revealed around 7% complications after the second stage, the principal complications being 3% fistulas, followed by 2% strictures and 1.5% requiring surgical revision of the meatus. By contrast, in this issue of The Journal Leslie et al (page 1077) paint a considerably less optimistic picture. Overall a third of their patients had complications after second stage urethroplasty, attributed largely to irregular and unpredictable graft contracture after the first stage. The institution was averaging only 6 such cases per year, operated on by 5 different pediatric urologists. Therefore, some of these surgeons were likely still on the steep part of the buccal mucosa learning curve. Other multi-operator institutions have also reported similarly high morbidity.4 Such disparate results suggest a significant learning curve with buccal mucosa and so it is perhaps not for the inexperienced urethral surgeon. Why did Leslie et al experience so many poor grafts? Filipas et al stated from porcine research 0022-5347/11/1853-0777/0 THE JOURNAL OF UROLOGY® © 2011 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
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RESEARCH, INC.
that buccal mucosa grafts have no inherent tendency to contract.5 Therefore, lumpy or contracted grafts must be the result of suboptimal graft take, perhaps due to poor vascularity of the wound bed or perhaps infection. It must be appreciated that buccal grafts are thick compared with inner preputial skin even after thorough removal of the bulky yellowish adventitial layer. To take perfectly thicker grafts requires an ideal recipient wound bed. Certainly in hypospadias salvage surgery, scarring and compromised vascularity of the wound bed must be considerations. Furthermore, if the wound beds are left exposed and allowed to desiccate under operating lights while grafts are being prepared, this can further compromise the vascularity. The graft harvesting technique may also be a factor. A graft may be excessively traumatized through rough handling with coarse instruments, by using blunt scissors to “chew” away the adventitial layer or by allowing the graft surface to dry out during the trimming process. Finally, individual biological variation may influence graft healing and maturation, given that in some patients skin wounds and grafts heal with ideal thin pliable scars while in others, identical wounds may heal with prolonged hypertrophy or even keloid scars. Leslie et al are wise to recommend creating a urethral plate that is initially wider than required. Early contraction is quite common and with long grafts it is not unusual for transient chordee to develop. However, this usually resolves within 4 to 6 months as the grafts mature and regain elasticity, perhaps aided by the tissue expansion effect of erections. While the majority of reconstructed urethral plates mature to approximately the originally designed dimensions, persistent narrowing of the plate does occur in some patients, and this is to a variable and unpredictable degree, thus the advantage of staged buccal tubes. At the second stage surplus graft width can be discarded or alternatively a shortfall augmented, allowing for the design of optimal urethral and meatal dimensions. While most grafts remain pink, smooth and pliable after the first stage, even if on occasion it has Vol. 185, 777-778, March 2011 Printed in U.S.A. DOI:10.1016/j.juro.2010.12.015
www.jurology.com
777
778
BUCCAL MUCOSA GRAFTS
been necessary to delay the second stage for several years, a minority of buccal grafts rapidly develop surface keratinization when left exposed. Typically the patient may peel off a layer of dry skin from the graft once or twice a week when in the shower, although the underlying graft appears healthy. After a second stage procedure keratinization of the exposed meatal margins may persist. Indeed 1.5% of patients in my series found this to be sufficiently troublesome to warrant meatoplasty to trim off exposed mucosa or to try and turn in the exposed meatal margins. Whether this surface layer represents dried secretions from mucosal glands, as suggested by some, or whether there is true keratinization of the graft surface, and whether it is avoidable or represents biological variation, is unclear. Do buccal substituted urethras keep pace with genital growth in adolescence? While genital skin is laden with androgen receptors and can be expected to grow rapidly in response to the hormonal
surge at puberty, the mouth is not programmed for rapid adolescent growth. Anecdotal evidence is reassuring in this respect, with grafts seeming to take on growth characteristics of the recipient site rather than retaining those of the donor site. Certainly in my own experience I have not encountered problems with urethral growth even with extensive buccal graft substitutions in childhood. Although followup has been based mostly on observation or description of the urinary stream rather than objective measurements, nevertheless some of the young adult patients have allowed me to calibrate the penile urethra with an 18Fr catheter in the outpatient clinic and I have been reassured as to the adequacy of the urethra. Buccal mucosa can be an excellent graft material, but like a prima donna it is prone to capricious and perplexing behavior. It is good but not perfect. Aivar Bracka Dudley, United Kingdom
REFERENCES 1. Duckett JW, Coplen D, Ewalt D et al: Buccal mucosal urethral replacement. J Urol 1995; 153: 1660. 2. Baskin LS and Duckett JW: Buccal mucosa grafts in hypospadias surgery. Br J Urol 1995; 76: 23.
3. Bracka A: Hypospadias repair: the two-stage alternative. Br J Urol 1995; 76: 31. 4. Bracka A and Fisch M: Urethroplasty for hypospadias. In: Atlas of Reconstructive Penile Surgery. Pacini Editore 2010, p 218
5. Filipas D, Fisch M, Fichtner J et al: The histology and immunohistochemistry of free buccal mucosa and full-skin grafts after exposure to urine. BJU Int 1999; 84: 108.
AND
RESEARCH, INC.
that buccal mucosa grafts have no inherent tendency to contract.5 Therefore, lumpy or contracted grafts must be the result of suboptimal graft take, perhaps due to poor vascularity of the wound bed or perhaps infection. It must be appreciated that buccal grafts are thick compared with inner preputial skin even after thorough removal of the bulky yellowish adventitial layer. To take perfectly thicker grafts requires an ideal recipient wound bed. Certainly in hypospadias salvage surgery, scarring and compromised vascularity of the wound bed must be considerations. Furthermore, if the wound beds are left exposed and allowed to desiccate under operating lights while grafts are being prepared, this can further compromise the vascularity. The graft harvesting technique may also be a factor. A graft may be excessively traumatized through rough handling with coarse instruments, by using blunt scissors to “chew” away the adventitial layer or by allowing the graft surface to dry out during the trimming process. Finally, individual biological variation may influence graft healing and maturation, given that in some patients skin wounds and grafts heal with ideal thin pliable scars while in others, identical wounds may heal with prolonged hypertrophy or even keloid scars. Leslie et al are wise to recommend creating a urethral plate that is initially wider than required. Early contraction is quite common and with long grafts it is not unusual for transient chordee to develop. However, this usually resolves within 4 to 6 months as the grafts mature and regain elasticity, perhaps aided by the tissue expansion effect of erections. While the majority of reconstructed urethral plates mature to approximately the originally designed dimensions, persistent narrowing of the plate does occur in some patients, and this is to a variable and unpredictable degree, thus the advantage of staged buccal tubes. At the second stage surplus graft width can be discarded or alternatively a shortfall augmented, allowing for the design of optimal urethral and meatal dimensions. While most grafts remain pink, smooth and pliable after the first stage, even if on occasion it has Vol. 185, 777-778, March 2011 Printed in U.S.A. DOI:10.1016/j.juro.2010.12.015
www.jurology.com
777
778
BUCCAL MUCOSA GRAFTS
been necessary to delay the second stage for several years, a minority of buccal grafts rapidly develop surface keratinization when left exposed. Typically the patient may peel off a layer of dry skin from the graft once or twice a week when in the shower, although the underlying graft appears healthy. After a second stage procedure keratinization of the exposed meatal margins may persist. Indeed 1.5% of patients in my series found this to be sufficiently troublesome to warrant meatoplasty to trim off exposed mucosa or to try and turn in the exposed meatal margins. Whether this surface layer represents dried secretions from mucosal glands, as suggested by some, or whether there is true keratinization of the graft surface, and whether it is avoidable or represents biological variation, is unclear. Do buccal substituted urethras keep pace with genital growth in adolescence? While genital skin is laden with androgen receptors and can be expected to grow rapidly in response to the hormonal
surge at puberty, the mouth is not programmed for rapid adolescent growth. Anecdotal evidence is reassuring in this respect, with grafts seeming to take on growth characteristics of the recipient site rather than retaining those of the donor site. Certainly in my own experience I have not encountered problems with urethral growth even with extensive buccal graft substitutions in childhood. Although followup has been based mostly on observation or description of the urinary stream rather than objective measurements, nevertheless some of the young adult patients have allowed me to calibrate the penile urethra with an 18Fr catheter in the outpatient clinic and I have been reassured as to the adequacy of the urethra. Buccal mucosa can be an excellent graft material, but like a prima donna it is prone to capricious and perplexing behavior. It is good but not perfect. Aivar Bracka Dudley, United Kingdom
REFERENCES 1. Duckett JW, Coplen D, Ewalt D et al: Buccal mucosal urethral replacement. J Urol 1995; 153: 1660. 2. Baskin LS and Duckett JW: Buccal mucosa grafts in hypospadias surgery. Br J Urol 1995; 76: 23.
3. Bracka A: Hypospadias repair: the two-stage alternative. Br J Urol 1995; 76: 31. 4. Bracka A and Fisch M: Urethroplasty for hypospadias. In: Atlas of Reconstructive Penile Surgery. Pacini Editore 2010, p 218
5. Filipas D, Fisch M, Fichtner J et al: The histology and immunohistochemistry of free buccal mucosa and full-skin grafts after exposure to urine. BJU Int 1999; 84: 108.