Biochemical analysis of urethral collagen content after tubularized incised plate urethroplasty: an experimental study in rabbits

Selecting the right method for hypospadias repair to achieve optimal results for the primary situation

BACKGROUND

Over the past two decades, Snodgrass tubularized incised plate (TIP) urethroplasty has become one of the dominant surgical techniques with wide applications and excellent cosmetic results. However, TIP has many limitations. We performed a retrospective study at our department and assessed the outcome of the inlay internal preputial graft for extending the applications of TIP.

METHODS

Between January 2009 and December 2013, we performed a retrospective study consisting of approximately 508 primary distal and moderate cases. Patients with primary distal hypospadias who had mild or no chordee and good penile development were divided into the following 3 groups based on their procedures: (1) classic TIP hypospadias repair group (n = 198); (2) inlay buccal mucosa graft group (n = 150); and (3) inlay internal preputial graft group (n = 160). The median age was 1.6 years (range 1-4 years). Our data were analyzed statistically by the Chi square test with P < 0.05 indicating significant differences.

RESULTS

The mean follow-up period was 18 months (range 6‒24 months). In the classic TIP group, the incidence of urinary fistula and meatal stenosis were both 3.0 % (6/198); in the inlay buccal mucosal graft group, the incidence of urinary fistula was 3.3 % (5/150), and the incidence of stenosis was 2.7 % (4/150); and in the inlay internal preputial graft group, the incidence of urinary fistula was 3.1 % (5/160), and the incidence of meatal stenosis was 4.4 % (7/160). The success rates of each group were as follows: the classic TIP group has a success rate of 93.9 % (186/198); the inlay buccal mucosa graft group had a success rate of 94.0 % (141/150); and the inlay internal preputial graft group had a success rate of 92.5 % (148/160). There were no statistically significant differences between the 3 groups with respect to complication rates.

CONCLUSIONS

As the inner foreskin Snodgraft does not appear to be worse than the buccal mucosa graft, it is a good method for hypospadias repair, and this method is not inferior to TIP.

Urethral musculature and innervation in the female rat

AIMS

The urethral sphincter and urethral muscle innervation are critically involved in maintaining continence, especially in the female. However, the urethral muscle type and distribution, as well as the urethral nerves are far from being well documented. Our aim was to clearly identify the distribution of urethral striated muscle, smooth muscle, and urethral nerves.

METHODS

In a cohort analysis of 3-month-old female Sprague-Dawley rats, cross and longitudinal sections of female rat urethra were extensively investigated using morphological techniques. Urethras were harvested to the sections, in order to provide both global and detailed visions of the urethra. H&E, Masson's Trichrome, phalloidin and immunoflourence stains were used. The cytoarchitecture, nitrergic, and cholinergic innervations were mainly investigated. Different layers of the segments of urethra were traced to draw curve graphs that represent the thickness of each muscle layer of urethral wall.

RESULTS

The results showed that the primary peak of striated muscle is in the middle urethra. The inner layer close to mucosa was found to contain longitudinal smooth muscle. Near the bladder orifice, the circular smooth muscle dominates, which becomes thinner distally throughout the rest of urethra. In the middle urethra the vast majority of the urethral muscle are circularly oriented striated muscle cells. Typical nerve endings were present in high power images to show the different characteristic features of nerve innervation.

CONCLUSIONS

This study has illustrated the detailed morphological structure and innervations of the normal female rat urethra and can serve as a basis for further study of stress urinary incontinence (SUI).

Reduced flow after tubularized incised plate urethroplasty--increased fibrogenesis, elastin fiber loss or neither?

PURPOSE

Low urinary flow rates are common after tubularized incised plate urethroplasty but the etiology remains unclear and may be related to low urethral compliance due to abnormal collagen concentrations and/or fewer elastic fibers in the healed urethral plate. We hypothesized that inserting a preputial mucosal graft over the dorsal raw area after the midline incision may avoid scarring and improve urethral compliance.

MATERIALS AND METHODS

Adult rabbits were submitted to tubularized incised plate urethroplasty with or without inlay preputial graft according to a previously described protocol. Tissular concentrations of collagens I, III, IV, VI, VIII and XIII were measured. Histomorphometric analysis was used to quantify elastic fibers in the urethra. Tubularized incised plate urethroplasty with and without inlay preputial graft was compared to normal rabbit urethras (controls).

RESULTS

mRNA concentrations for collagens I, II and XIII were similar between controls and operated rabbits. The proportions between collagens I and III were 1.05, 0.87 and 1.21, respectively, in controls and animals undergoing tubularized incised plate urethroplasty with and without inlay preputial graft. mRNA concentrations for collagen IV and collagens VI/VIII tended to be higher and lower, respectively, in the operated urethras, despite showing statistical significance only for collagen VIII in animals undergoing tubularized incised plate urethroplasty with inlay preputial graft vs controls (p=0.02). The operated animals did not demonstrate a reduced number of elastic fibers in the urethral tissues compared to controls.

CONCLUSIONS

Elastic fiber number and distribution were similar between tubularized incised plate urethroplasty cases and controls, suggesting that decreased concentrations of elastic fibers do not explain the reduced urethral compliance after tubularized incised plate urethroplasty. The raw area determined by the dorsal urethral incision regenerated after standard tubularized incised plate urethroplasty, while cicatrization with fibrosis occurred in correspondence to the grafted areas after tubularized incised plate urethroplasty with inlay preputial graft.

A biomechanical, histological and biochemical study in an experimental rabbit hypospadias repair model using scanning acoustic microscopy

OBJECTIVE

To investigate the biomechanical, histological and biochemical properties of rabbit urethra at long-term follow up after hypospadias simulation and acute repair.

MATERIALS AND METHODS

Thirty-eight white New Zealand male rabbits underwent experimental creation of a hypospadias-like defect and acute repair (mobilization and advancement, tubularized incised posterior urethral plate (TIP), modified TIP) and sham operation. After 23 weeks all groups + controls underwent biomechanical, histological and biochemical assessments.

RESULTS

The mobilization and advancement group showed a higher stiffness compared to the TIP groups (P < 0.05) in the posterior urethra, whereas the TIP group was stiffer compared to the other two operative groups (P < 0.001) in the ventral urethra. In the dorsal urethra, the mobilization and advancement group and the modified TIP group had a higher collagen content compared to shams (P < 0.05). No differences in collagen content were found between groups in the ventral urethra. A correlation between acoustic and histological layers was found, partially related to collagen content.

CONCLUSION

The urethras had different microelastic properties in different layers of the dorsal and ventral urethra, with higher stiffness in the connective tissue layers surrounding and within the urethra. The repaired urethras had partially recovered their elasticity at micrometer resolution at long-term follow up. Scanning acoustic microscopy elucidated structure-function relationships at microscopic level in normal and operated urethra.

Tubularized incised plate urethroplasty for distal hypospadias: A literature review

The tubularized incised plate (TIP) urethroplasty or Snodgrass procedure has gained worldwide acceptance for distal hypospadias repair due to its low complication rate, good cosmetic result, and technical simplicity. As a result, several articles have been published concerning various aspects and subtle variations of this procedure. The aim of this review is to critically and systematically analyze the published complication rates of TIP repair for distal hypospadias in children. We also reviewed the surgical modifications that have been introduced to the original technique and discussed the potential impact on the final outcome of the Snodgrass procedure.

Biomechanical and Biochemical Assessment of Properties of the Anterior Urethra After Hypospadias Repair in a Rabbit Model

PURPOSE

We created a rabbit model to test hypospadias operations and investigate the biomechanical properties of the urethra at long-term followup using biomechanical and biochemical assessments.

MATERIALS AND METHODS

A total of 38 New Zealand White rabbits were randomized into 4 groups, including controls, sham operation and 2 operation groups (experimental creation of a hypospadias-like defect and acute repair, respectively). In operation group 1 the ventral urethral wall and dorsal plate were longitudinally incised, half of the ventral urethral wall was excised (hypospadias-like defect) and the incised urethra was tubularized (tubularized incised posterior plate urethroplasty group). In operation group 2 the urethra was mobilized from the corpora cavernosa, excised in its distal end (hypospadias-like defect) and advanced to the glanular tip (mobilization and advancement group). At 23 weeks postoperatively biochemical and biomechanical assessments were performed.

RESULTS

Maximum urethral strength and stiffness, strain at maximum load and the collagen weight fraction were not significantly different among the groups. Urethral diameter was larger and the total amount of collagen was higher in the mobilization and advancement group only (p <0.05). The mechanical quality of urethral collagen was decreased in the 2 operation groups (p <0.05).

CONCLUSIONS

This animal model proved to be useful for testing hypospadias operations and urethral mechanical properties. At long-term followup after experimental hypospadias repair biochemical and biomechanical assessments showed no differences among the groups in mechanical strength, strain and stiffness, and no indication of fibrosis. Consequently testing new hypospadias repair techniques and evaluating their biomechanical long-term results could be performed using hypospadiac animal models before clinical use.

The effect of indwelling catheter on OH-proline in the urethral wound: an experimental study

OBJECTIVE

To investigate the effect of catheterization on urethral wound healing by measuring OH-proline.

METHODS

Eighteen male New Zealand albino rabbits were divided equally into three groups. In the control group, urethral tissue samples were taken from the ventral penile surface. In group II, the ventral penile surface was incised and primarily repaired by 6/0 polydioxanone. In group III, the incised urethra was repaired by 6/0 polydioxanone and a urethral catheter was inserted. Tissue samples were taken on the 20th postoperative day in groups II and III. Tissue OH-proline levels were measured by the method of Bergman and Loxley. The Kruskal-Wallis statistical test was used for evaluation.

RESULTS

OH-proline values as microg/mg dry tissue were 16.43+/-2.68 in the control group, 14.47+/-1.82 in group II and 14.63+/-0.63 in group III. There was no significant difference between the three groups (P>0.05).

CONCLUSION

Use of a urethral catheter does not appear to have a direct effect on collagen synthesis in wound healing.

The midterm success rates of tubularized incised plate urethroplasty in reoperative patients with distal or midpenile hypospadias

To review the midterm results of tubularized incised plate (TIP) urethroplasty (Snodgrass method) in reoperative patients with distal or midpenile hypospadias. The results of TIP urethroplasty in 37 patients who had previously failed hypospadias repair were reviewed. Of the patients, 21 (56.8%) had coronal, 11 (29.7%) had subcoronal, and 5 (13.5%) had midpenile hypospadias. The mean age was 4.1 (2-16) years. Twenty-three patients had one operation and 14 patients had two operations previously. Of all the patients, 14 did not have a foreskin because of circumcision. The urethral plate had been disturbed in 6 patients, but there was not apparent scarring of the plate. Postoperative follow-up was 2.3 years with a range of 1.1-3.9 years. Genital examination, urethral calibration, and uroflowmetry were performed in control. Satisfaction of the families about the function and appearance of penis was also evaluated. Successful functional and cosmetic results were achieved in 29 patients (78.4%). All the families were happy with penile aesthetic appearance. The urethral plate seemed healthy at the operation in nine patients who had undergone TIP urethroplasty before and the outcomes were successful in eight of them. The operation was successful in 19/23 (82.6%) patients who had undergone one operation before and in 10/14 (71.4%) patients with two operations as well (P < 0.05). In addition, sufficient outcomes were obtained in also 11 of the 14 patients with circumcision. The success rate was higher in patients <5 years (P < 0.05). The rate was also higher during the recent period (2001-2003) since the experience we had increased (P < 0.05). TIP urethroplasty was unsatisfied in four of the six patients who had had disturbed urethral plate before and in five of eight patients who did not have sufficient amount of dartos tissue for flap to cover neourethra. Complication was observed in eight patients (21.6%): four had a pinpoint fistula, two had wound dehiscence, one had meatal stenosis, and one had mild meatal regression and a short neourethral stricture. All of these complications were repaired successfully at a later date. The mean hospital stay was 4.6 days. TIP urethroplasty provides good functional and cosmetic midterm outcomes in most of the reoperative patients with distal or midpenile hypospadias unless contraindicated by previous resection or gross scarring of the urethral plate. This procedure seems not to disturb the urethral plate and, therefore, it can be applied on reoperative patients who had undergone TIP urethroplasty before. It can also be used in a circumcised patient when there is a lack of foreskin.