Regenerative urethroplasty in reoperative hypospadias: Buried strip principle revisited.

AIM: Reporting the feasibility of the Denis Browne (buried strip) principle along with tunica vaginalis (TV) pedicled wrapping of the strip in reoperative urethroplasty in hypospadias.
MATERIALS AND METHODS: Over a period of 5 years, 32 patients presented with failure of previous urethroplasty and the range of failure was between 2 and 6 times; mean 2.5 times. Mean age was 12.9 (range 2 to 26 years) years. "Buried strip" urethroplasty (i.e., without tubularization of urethral plate) and wrapping with TV were done along with supra pubic cystostomy (SPC) for diversion of urine. Mean follow-up was 29.8 (range 12 to 56 months) months.
RESULTS: One patient had fistula and vertical slit meatus was possible in 26 patients. The flow of urine was satisfactory in 31 patients and one patient developed pouch in penile urethra.
CONCLUSIONS: The buried strip along with the additional coverage with TV was found to be simple and effective in salvaging the failed urethroplasty.

INTRODUCTION

Reoperative procedures are a formidable challenge in hypospadias as the vascularity and the healing is poor.[1-3] The procedures applicable to virgin hypospadias do not show similar outcome in reoperation of hypospadias[4] and complications may be as high as 56%.[5] In re-do urethroplasty, the skin or residual urethral plate or skin mixed with residual urethral plate, bits of buccal mucosa [Figure 1] i.e., tissue intended to be urethra (TITBU), is less vascular than the native urethral plate. In addition, during tubularization, vascular supply may be diminished due to the gradual circumferential separation of TITBU from subcutaneous tissue. This ischemia is aggravated further on the TITBU from unintended tension by the stitches for tubularization over a catheter.

Figure 1

Skin, residual urethral plate, and bits of residual buccal mucosa

In our procedure, by adopting the buried strip principle of Denis Browne,[6] both are avoided by keeping the strip in situ and allowing it to regenerate on a tube as a scaffold. From our little experiences of urethroplasty[78] with tubularized incised plate (TIP) procedure, we realized that the most popular TIP procedure[4] is, in fact, depending on the regeneration of the epithelium in the gap of the incised plate to achieve the adequate caliber of the neo-urethra. Both in the procedures of Denis Browne and the Snodgrass, buried strip and created gap in the incised plate are regenerating respectively and similarly. Basically Snodgrass procedure is a regenerative urethroplasty.

We report our experience and outcome of regenerative urethroplasty of “buried strip” concept, straight-forwardly accrediting Denis Browne, for the reoperative urethroplasty in hypospadias in combination with the tunica vaginalis pedicled flap (TVPF).

MATERIALS AND METHODS

Thirty two patients of mean age 12.9 years (range 2 to 26 years) were enrolled. There were 25 failed previous urethroplasties, three had 1st stage chordee correction and attempt of buccal mucosal graft (BMG) and rest four patients had chordee correction without BMG. Seven patients were above the mean age. They were included in this study after obtaining the informed consent. Surgeries were done from December 2005 to November 2010. Out of those 25 patients, 16 had skin or a portion of residual urethral plate on the ventral surface of penis along with or without fistula and the rest nine patients had multiple large fistulas. Previous attempt of urethroplasty were in the range of 1 to 6 (mean 2.5) times.

Positions of the hypospadiac meati on inspection was found to be scrotal in two, peno-scrotal in eight, mid penile in 10 and distal penile in 12. In five patients, the shapes of the meati were distorted due to the previous attempt of making the meatus at the tip of glans ignoring the position of ‘cleft meatus’ [Figure 1]. The patients with penile chordee were excluded from this study. In all patients suprapubic cystostomy (SPC) was done for the drainage and diversion of urine and for the early removal of PUC to avoid destruction of the reconstructed glans.

A ‘U’ shaped incision was made encompassing the hypospadiac meatus and ending in the glandular ‘cleft meatus’ to create a rectangular island of TITBU separated from rest of the penile skin after degloving [Figure 2] in 23 patients. In the other 9 patients, ventral longitudinal incision was made to open up the urethra under the multiple fistulas prior to that incision and degloving. The width of the TITBU varied between 4 and 8 mm and that variation depended on the width of the cleft meatus. Midline incision made only at the cleft meatus for the “hinging”[9] of the glandular urethral plate in all patients and to accommodate the per urethral catheter (PUC) without the suture tension in the glanuloplasty.

Figure 2

TITBU after degloving

A catheter (PUC) of appropriate size was inserted into the bladder and placed over the TITBU with one or two loose tie-over stitches to keep it in position. PUC was intended as a scaffold and was kept clamped and less mobile in post operative dressings for 5 to 6 days. Tunica vaginalis pedicled flap (TVPF) were harvested [Figure 3] from right testis and left was left for future as a convention.[8] In some situations, in distal penile or mid penile hypospadias, penile incisions were not long enough to allow the testis to be prolapsed into the dissected area.[8] For that, separate incision in the scrotum was required for tunneling up the TVPF that wrapped the strip of TITBU with PUC over it. TVPF was sewn not at the edge of TITBU but to the tissues lateral to the TITBU, just as a wrap [Figure 3] not as an onlay. Glans wings were just wrapped around the TITBU with catheter and tunica vaginalis with 4-0 catgut. Dorsal penile skin was rotated to ventrum for closure and ventral midline stitches were avoided. On 10 to 12th day, the patients were allowed to void per urethra as the clinical status of wound was found to be good. SPC was removed on next day provided there was no penile edema due to extravasation.

Figure 3

TVPF wrap over the TITBU

Calibration, not the dilatation of urethra in all patients was advised to be done by the parents after 6 to 8 weeks of surgery only on suspicion of decreased flow and in follow up clinic. In 28 patients uroflowmetry was done after a period of 12 months after surgery. USG for the kidney, ureter and bladder was done in 26 patients after 12 months of urethroplasty to find out any features of back pressure changes were present or not. After that, uroflometric check up was continued on every follow-up and USG was advised only on suspicion of back pressure changed on decreased flow status. Only five parents consented for urethoscopy and was done after 6 to 12 months.

RESULTS

The mean follow-up was 29.8 (range 12 to 56 months) months. In all patients’ neo-meatus and glandular reconstruction maintained their position and shape respectively and fistula near corona occurred in two patients. Vertical slit meatus was the result in 26 patients. Thirty one patients and their parents were satisfied with the flow and calibration with expected size during follow-up. One patient with meatal stenosis had straining and decreased flow. On ascending urethrogram a urethral pouch was detected near distal urethra. He was re-operated for reduction urethroplasty by plication of the urethral pouch. The patient is doing well now.

In uroflowmetric assessment, 23 patients had Qmax (maximum flow rate) within 2 and 3 SD below the mean value and five had the Qmax within the normal range as per the chart of Segura.[10] USG found no signs of back pressure change in any patients. Follow up urethroscopy was done in five patients only. Identification and demarcation between the normal and the regenerated urethra was possible. The regenerated urethra looked paler than its normal counterpart. In two patients, penile edema appeared on voiding after clamping of the SPC catheter; needed continuation of the SPC for another week. No patient developed suture track fistula (STF) in that span of follow-up. One patient developed mid penile fistulas requiring further surgical procedure. One patient is now enjoying paternity of two children.

DISCUSSION

SPC is an older procedure of urinary diversion but it is effective and preferred by some authors.[11] It helps to avoid the bad effects of post-operative penile erection as well as the damages of the reconstructed glans and meatus from the PUC. For that PUC is kept less mobile and removed earlier. Similarly midline “hinging incision” only in the glandular urethral plate[8] is also effective in creation of the vertical slit meatus. Absence of STF is possibly due to the use of absorbable catgut. We have no standard uroflowmetric nomogram for the assessment of uroflow after the urethroplasty. Hence we had to depend on the normal nomogram from Segura.[10] That obviously shows the values below the normal ranges.

Overall complication in this series was about 15.6% and that is comparable to that of other series[12-14] ranging from 20 to 35.7%. Further surgical intervention was considered as failure (6.25%) and that was necessary in two patients only.

Magnitude of regenerative potential of epithelial tissue in subcutaneous adipose tissue is not yet measured. But in tissue engineering, it is possible to get a football field size epithelial tissue from a piece of one square cm within 8 weeks.[15] Regeneration may even be possible from the fibrosed urethra as their cells retain the genetic stability.[16]

The concept of “buried strip” from Dupley (1880), Hamilton Russel (1915) and Denis Browne (1949) basically follows the principles of regeneration.[17] But the exact principles of regeneration are missing in their descriptions unlike recent appreciation of the regeneration[15] of tissues in vivo. Johanson (1953) applied similar principle in urethroplasty for long anterior urethral stricture.[18] According to them and to the principle of regeneration, tubularization is not mandatory. The regeneration of the epithelium will occur from a skin strip buried into subcutaneous tissue to create a tube by the nature[19] as the basal layer is the source of dividing cells, some of which are immortal stem cells.[20] The adipose tissue in the subcutaneous layer also has got abundant stem cells.[21] The lineage cells from that differentiate into an endothelial cell to participate in new blood vessel formation in vivo[22] and that is essential in the regeneration of tissues. On the other hand, tubularization is a good option, but limitations are imposed by the width of the plate.[23]

Loss of popularity of the “buried strip” procedure is due to the high complications blamed towards the overlapping skin suture line to buried strip (TITBU) as well as the outcome obtained by them is not duplicated by others. To obviate that problem Durham Smith (1973) conceptualized the barrier layer, i.e., “pant over vest”, to avoid the overlapping of the suture lines of urethra and skin to minimize occurrence of urethro-cutaneus fistula.[24] Nowadays many authors prefer the vascular flaps[482526] in urethroplasty for hypospadias for the same purpose as well as for vascular enhancement. Vascular flap from the TVPF also has got same role. Similarly rotation of thicker and more vascular dorsal penile skin to ventrum follows the same concept of vascular enhancement. These are lacking in the procedure of Denis Browne[6] and Johanson[18] causing high complications. We have combined both the TVPF and rotation of dorsal skin to ventrum to minimize those.

Many surgeons feel secure by the ‘visible’ tube rather than the ‘virtual’ concept of “buried strip” or the regenerative principle. Recently tubularized incised plate (TIP) procedure has gained wide acceptance[27] for primary hypospadias repair. It has also been studied that the raw area made after the “relaxing incision” on the urethral plate, regenerates from the healthy epithelial tissue. But the sutured and repaired area shows desmoplastic (fibrosis) response.[28] This fibrosis is proportional to the tension causing blanching and ischemia in the bivalved plate by the sutures for tubularization over a catheter. So wider (8 mm or more) urethral plate is suggested by some authors[2930] to avoid that tension on suture line causing high incidence (23.1 to 55%) of complications.

In expert hands, the tension is released by adequate deep relaxing incision along with undermining of the bivalved urethral plate[31] even in 4 mm of plate.[30] In that way, urethral plate of 4 mm width may be sufficient[32] for tubularization if the midline incision of the TIP is considered as “relaxing”. Otherwise “hinging” incision[8] demands wider urethral plate[30] to avert the tension-blanching-ischemia-fibrosis cascade.

In TIP procedure, the unwanted effect of the desmoplastic reaction on the ventral aspect due to suturing is counterbalanced by the ingrowth of normal tissue (i.e., regeneration) in the cleft made by “relaxing incision”. The resultant caliber of the neo-urethra depends on a balance of the desmoplastic reaction on the ventrum and the regeneration of normal tissue on the dorsum. Hence TIP is basically satisfying both the principles of ‘tube urethroplasty’ and the concept of “buried strip”.

Another contributing factor of the ischemia is the inadvertent circumferential separation and stretching of the vasculature of TITBU during the tubularization. We keep the TITBU undisturbed to allow them to regenerate over the urethral catheter as a scaffold avoiding this tension-blanching cascade.

CONCLUSIONS

The “buried strip” concept is an old, abandoned and unknown to many and it is in oblivion! The trails of the popularities of Dupley, Hamilton Russel, Denis Browne, Johanson by name are still identifiable by the pediatric surgeon, plastic surgeon, urologists and others. But the actual procedure and the regenerative concept of the “buried strip” is forgotten by many. This is the main reason of the forgetfulness in the attribution of that concept in the most popular TIP procedure. Notwithstanding, TIP procedure is indirectly validating the “buried strip” concept in ‘dignified disguise’.

We identified that the “buried strip” principle along with the additional coverage with TV is technically simple and effective for the reoperative urethroplasty.