Can Grafted Tubularized Incised Plate Urethroplasty be Used to Repair Narrow Urethral Plate Hypospadias? Its Functional Evaluation Using Uroflowmetry.

AIM: Using uroflowmetry, the aim of this study is to determine the functional results of the grafted tubularized incised plate (GTIP) urethroplasty used to repair poor urethral plate hypospadias. SETTINGS AND
DESIGN: Seventy-one patients (mean age: 5.7 years, follow-up: 1-5.5 years) were selected from those who underwent surgery using the GTIP technique from 2013 to 2015 at our institution.
METHODS: Patients included were able to void voluntarily and had no fistula. The flow pattern, maximum urinary flow rate (Qmax), voided volume (vv), average flow rate, and voiding time were measured. The results were expressed as percentiles and interpreted according to Siroky nomogram. The Qmax was considered normal if >25th percentile, as equivocally obstructed when in the 5th-25th percentile, and obstructed if <5th percentile.
RESULTS: Hypospadias was distal in 45, mid penile in 17 and proximal penile in 9. The uroflow curve was bell-shaped in 24 (30%), interrupted in 9 (14%), slightly flattened in 31 (46%), and a plateau in 7 (10%). Flow rate nomograms revealed that 49 (68%) were above the 25th percentile, 9 (17%) were below the 5th percentile, and 13 (15%) were between these ranges. Eleven patients showed improvement in the flow curve and maximum urinary flow rate (Qmax) in follow-up uroflowmetry.
CONCLUSION: GTIP repair provides satisfactory functional results. A long-term follow-up is needed to confirm these results. Copyright:

INTRODUCTION

Hypospadias is a common congenital anomaly affecting the penis that, either treated or untreated, can have functional, cosmetic, and psychosexual consequences extending into adulthood.[1]

The objectives of surgical repair are to create a cosmetically satisfactory appearance, a straight penile shaft during erection, and a urethral opening distally at the glans. The reconstructed urethra should have an adequate caliber and grow with the child. Evaluation of outcome includes complications, cosmetic appearance of the penis, functional outcome, quality of life, and psychosexual life.[2]

To measure outcome objectively, efforts have been made using structured scoring systems (Hypospadias Objective Scoring Evaluation and Pediatric Penile Perception Scoring), patient questionnaires, photographic evaluation, and uroflowmetry to assess voiding function.[3] Urinary flow studies provide an objective measurement of urethral function.[4] The advantages of uroflowmetry as a procedure to quantify the outcome are the simplicity with which the investigation can be accomplished, the noninvasive nature of the examination and the acceptability to patients. The results cannot be biased by the interpretation of the operator making it a suitable modality for use in routine follow-up.

In tubularized incised plate (TIP) urethroplasty, an incision in a healthy urethra heals with re-epithelialization with normal tissue, and the suture line heals with an inflammatory response. However, many patients have an obstructed flow clinically, with a thin stream and long-voiding duration after TIP repair mainly in mid and proximal varieties. Marte et al.[5] reported that, after mean follow-up of 20 months, 33% of the boys had abnormal flow curves after TIP repair. To overcome these complications in poor urethral plate hypospadias, we did grafted TIP (GTIP) urethroplasty. In this study, we evaluated the functional results of GTIP hypospadias repair using the uroflowmetry.

METHODS

This observational analytic study was performed in patients who underwent GTIP repair for hypospadias correction in this pediatric urology unit during 2013–2015.

In January 2015, a phone call and a letter were sent to 84 patients after obtaining approval from the ethical committee. Thirteen patients lost to follow–up, and in 71 boys, uroflowmetry was performed by medical measurement system. Patients were old enough to void voluntarily and fistula free. The parameters measured were the peak flow, voiding time, flow time, time to peak flow, and voided volume (vv). The peak flow (Qmax) and vv results were expressed as percentiles and interpreted according to Siroky nomogram. As described by Kaya et al.,[6] Qmax and vv were considered to be normal if they were >25th percentile, equivocal if they were between the 5th and 25th percentile range, and obstructed if they were <5th percentile.

RESULTS

In total, 71 patients were eligible for the study. The mean age at study was 5.7 years (range: 3.9–9.7 years). Hypospadias was distal penile in 45 (63.38%), mid in 17 (23.94%), and proximal penile in 9 (12.67%). Mean follow-up was 1–5.5 years. The uroflow curve was bell-shaped in 24 (33.8%) [Figure 1], interrupted in 9 (12.7%), slightly flattened in 31 (43.7%) [Figure 2], and plateau in 7 (9.9%) [Figure 3]. Flow rate nomograms revealed that 49 (69%) were above the 25th percentile [Figure 4], 9 (12.7%) were below the 5th percentile [Figure 5], and 13 (18.3%) were between these ranges [Figure 6]. Eleven patients showed improvement in the flow curve and maximum urinary flow rate (Qmax) at follow-up uroflowmetry.

Figure 1

Uroflow showing bell-shaped curve

Figure 2

Uroflow showing slightly flattened curve

Figure 3

Uroflow showing plateau-shaped curve

Figure 4

Nomogram showing Qmax >25th percentile

Figure 5

Nomogram showing Qmax <5th percentiles

Figure 6

Nomogram showing Qmax between 5th and 25th percentiles

DISCUSSION

Urethroplasty in hypospadias patients requires long-term follow-up to determine the functional consequences of the urethra. The urethral stricture after hypospadias repair is a well-documented complication of reconstruction with unknown long term after effects of asymptomatic stenosis.[7] The principal aim of the follow-up after hypospadias repair should be early detection of the obstruction. The reported incidence of poor flow rates after TIP repair is 7%–67%.[7]

Kolon and Gonzales described the technique of one-stage dorsal inlay inner preputial graft and noted to have no patients with meatal stenosis, neourethral stricture, urethrocutaneous fistula, or urethral diverticulum[8] and recommended in patients with a flat or narrow glans. Using the same technique, Gundeti et al.[9] reported low complication rate particularly in patients who lack a urethral groove or have small glans.

Urinary flow estimation reflects both urethral and bladder functions. We expect that most patients with hypospadias had normal bladder contractility so the results of urinary flow rates and the shape of the curve reproduce urethral function. It is notable that, in urethral strictures, Qmax is diminished and the flow pattern loses its normal bell shape and becomes flattened.[7] The Hagen–Poiseuille formula for flow in a rigid tube states that: where: F = flow, △P = pressure difference between the two ends of the tube, r = radius of the tube, η = viscosity of the liquid, and L = length of the tube. The similarity between the plateau curve and those with urethral strictures would tend to suggest that the problem may lie in the radius of the urethra (as this factor is raised to the fourth power in the Hagen–Poiseuille formula), but at what level is not known. The compliance of the walls of the tube is not taken into consideration in the Hagen–Poiseuille formula.

The literature offers theories endeavoring to explain weak flow rates following hypospadias repair. The rigidity of the neourethra has been proposed as a cause of weak flow rate[10] even in adequate caliber urethra.[11] Others claim that is related to the absence of the corpus spongiosum[12] and poor intravesical pressure during micturition. However, Olsen et al. found that there was no relationship between abnormal flow and the caliber of the neourethra.[13] The hypothesis additionally linked poor flow rate with the neourethral length of posturethroplasty patients, but it was contradicted with the result of the study conducted by Idzenga et al.[14] They showed that there was no effect of the length of neourethra against the flow rate, but the elasticity of the neourethral wall showed a significant effect.[4]

In our study, 49 patients (69.01%) had a normal Qmax, 13 (18.30%) were between the 25th and 5th percentiles, and 9 (12.67%) were below the 5th percentile. We observed that 3/9 (33.33%) of the patients who were below the 5th percentile for Qmax normalized after repeat uroflow done after 1 year and none of them required further intervention, while the other remained below the 5th percentile. We did urethral dilation in these patients but could not find any stricture. Moreover, from the intermediate group, 8/13 normalized in 1-year follow-up study. Hammouda et al. reported that 33% of patients after an intermediate follow-up of 2 years had flat curves with a low Qmax (below the 5th percentile).[15] In contrast, our study showed only nine patients (12.67%) having a plateau-shaped curve with low peak flow rates.

Holmdahl noticed an improvement of Qmax within an 8 months’ period.[16] Similarly, El-Hout et al. reported that flow rate parameters changed over time. They showed that 37% of initially flat curves became bell-shaped.[17] The gradual normalization of flow rates was suggested to result from postoperative softening of tissue.[16] We observed that although 22 of our asymptomatic children after GTIP repair showed suboptimal functional results initially, with extended follow–up, 11 (15.49%) patients displayed spontaneous improvement in most of these parameters, thus supporting the observations of previous authors.[18] This is possible because epithelialized neourethra is achieved right at the time of surgery.[19]

The importance of a plateau flow pattern or a Qmax below the 5th percentile is not recognized as there are limited reports of the long-term follow-up of asymptomatic patients with obstructive flows.[4] Andersson et al.[20] evaluated the results of TIP urethroplasty and showed to have spontaneous improvement in long-term follow-up. However, 32% of the boys still had asymptomatic obstructed flow patterns. Further, they included that utilization of TIP repair in proximal hypospadias had a poor stream. In our study, we found seven patients (9.85%) to have a plateau-shaped curve. No patient presented with overt urinary obstruction.

Shimotakahara evaluated GTIP repair and found to have lower overall complication rate[21] and recommended GTIP as the procedure of choice for patients undergoing primary hypospadias surgery. Mouravas et al.[22] observed lower neourethral stenosis and fistula rate, as compared to TIP repair, as a raw area is left in the dorsal urethra in TIP repair which is expected to leave some scarring and therefore relatively noncompliant and poor quality urethra.[2324]

Meatal stenosis is the main preoperative cause of urethral narrowing in patients with hypospadias. Studies[132526] have shown that the maximum flow rate was lower; uroflow curve and the voiding time were longer before correction in 6%–31% of hypospadias patients.

The present study has few limitations. The sample size was small and the cohort did not have preoperative uroflow study for comparison with postoperative results.

CONCLUSION

The GTIP technique gives satisfactory functional results in narrow plate hypospadias as confirmed by uroflowmetry. Grafting avoids risks related to re-epithelialization of a severe urethral plate defect, decreasing the incidence of stenosis and fistula. In selected cases, the GTIP yields satisfactory cosmetic and functional results for the treatment of narrow urethral plate hypospadias. A long-term follow-up study is needed for further evaluation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.