‘Waterproofing layers’ for urethrocutaneous fistula repair after hypospadias surgery: evidence synthesis with systematic review and meta-analysis

Abstract

Objective
To summarize the available evidence and to quantitatively evaluate the global results of different waterproofing layers in substantiating the UCF repair.

Material and methods
After defining the study protocol, the review was conducted according to the PRISMA guidelines by a team comprising experts in hypospadiology, systematic reviews and meta-analysis, epidemiology, biostatistics and data science. Studies published from 2000 onwards, reporting on the results of UCF closure after hypospadias repair were searched for on PUBMED, Embase and Google Scholar. Study quality was assessed using Joanna Briggs Checklist (JBI) critical appraisal tool. The results with different techniques were compared with the two samples independent proportions test with the help of Microsoft Excel, MedCalc software and an online calculator.

Results
Seventy-three studies were shortlisted for the synthesis; the final analysis included 2886 patients (71 studies) with UCF repair failure in 539. A summary of various dimensions involved with the UCF repair has been generated including time gap after last surgery, stent-vs-no stent, supra-pubic catheterization, suture material, suturing technique, associated anomalies, complications, etc. The success rates associated with different techniques were calculated and compared: simple catheterization (100%), simple primary closure (73.2%), dartos (78.8%), double dartos flaps (81%), scrotal flaps (94.6%), tunica vaginalis (94.3%), PATIO repair (93.5%), biomaterials or dermal substitutes (92%), biocompatible adhesives (56.5%) and skin-based flaps (54.5%). Several techniques were identified as solitary publications and discussed.

Conclusions
Tunica vaginalis and scrotal flaps offer the best results after UCF closure in the synthesis. However, it is not possible to label any technique as ideal or perfect. Almost all popular waterproofing layers have depicted absolute (100%) success sometimes. There are a vast number of other factors (patient’s local anatomy, surgeon’s expertise and technical perspectives) which influence the final outcome.

Full text

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Pediatric Surgery International (2023) 39:165
https://doi.org/10.1007/s00383-023-05405-1
ORIGINAL ARTICLE
‘Waterproofing layers’ forurethrocutaneous fistula repair
afterhypospadias surgery: evidence synthesis withsystematic review
andmeta‑analysis
PrativaChoudhury1· KomalKaurSaroya1· VisheshJain1· DevendraKumarYadav1· AnjanKumarDhua1·
SachitAnand1· ShashiMawar2· VivekVerma3· SiddharthKapahtia4· SameerKantAcharya5· RasikShah6·
MinuBajpai1· PrabudhGoel1
Accepted: 31 January 2023
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023
Abstract
Objective To summarize the available evidence and to quantitatively evaluate the global results of different waterproofing
layers in substantiating the UCF repair.
Material and methods After defining the study protocol, the review was conducted according to the PRISMA guidelines
by a team comprising experts in hypospadiology, systematic reviews and meta-analysis, epidemiology, biostatistics and
data science. Studies published from 2000 onwards, reporting on the results of UCF closure after hypospadias repair were
searched for on PUBMED, Embase and Google Scholar. Study quality was assessed using Joanna Briggs Checklist (JBI)
critical appraisal tool. The results with different techniques were compared with the two samples independent proportions
test with the help of Microsoft Excel, MedCalc software and an online calculator.
Results Seventy-three studies were shortlisted for the synthesis; the final analysis included 2886 patients (71 studies) with
UCF repair failure in 539. A summary of various dimensions involved with the UCF repair has been generated including
time gap after last surgery, stent-vs-no stent, supra-pubic catheterization, suture material, suturing technique, associated
anomalies, complications, etc. The success rates associated with different techniques were calculated and compared: simple
catheterization (100%), simple primary closure (73.2%), dartos (78.8%), double dartos flaps (81%), scrotal flaps (94.6%),
tunica vaginalis (94.3%), PATIO repair (93.5%), biomaterials or dermal substitutes (92%), biocompatible adhesives (56.5%)
and skin-based flaps (54.5%). Several techniques were identified as solitary publications and discussed.
Conclusions Tunica vaginalis and scrotal flaps offer the best results after UCF closure in the synthesis. However, it is not
possible to label any technique as ideal or perfect. Almost all popular waterproofing layers have depicted absolute (100%)
success sometimes. There are a vast number of other factors (patient’s local anatomy, surgeon’s expertise and technical
perspectives) which influence the final outcome.
Keywords Hypospadias· Urethrocutaneous fistula· Dartos· Tunica vaginalis· Buccal mucosal graft· Tissue glues· Bio-
adhesives· Dermal substitutes· PATIO
Shared first authorship between Prativa Choudhury and Komal Kaur
Saroya.
* Prabudh Goel
drprabudhgoel@gmail.com
1 Department ofPediatric Surgery, All India Institute
ofMedical Sciences, NewDelhi, India
2 College ofNursing, All India Institute ofMedical Sciences,
NewDelhi, India
3 Assam University, Silchar, India
4 Division ofNon-Communicable Diseases, Indian Council
ofMedical Research, NewDelhi, India
5 Department ofPaediatric Surgery, VM Medical College,
NewDelhi, India
6 Department ofPaediatric Surgery, SRCC Children’s
Hospital, Mumbai, India

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Introduction
Urethrocutaneous fistula (UCF) formation remains the
most common complication after hypospadias surgery and
other penile reconstructive procedures; the complication
is a nightmare both for the patient as well as the hypospa-
diologist. Exact etiology is obscure and may be related to
the patient (local anatomy), the surgeon (technique, tissue
handling or surgical finesse), the suture material or infec-
tious etiology. Multiple techniques have been described for
UCF repair with an equally large number of variations in the
respective techniques; considering the diversity of etiology
and the heterogeneity of results, none of them has yet been
considered the gold standard.
The utility of interposing additional layers of tissues
between the urethral repair and the penile skin in an attempt
to ‘waterproof’ the UCF repair and to prevent overlapping
suture lines has been widely accepted as an integral com-
ponent in the management of UCF. A large variety of such
tissues have been described and tested in individual stud-
ies including the local subcutaneous flaps or dartos, scro-
tal dartos, tunica vaginalis flaps or grafts, de-epithelialized
skin flaps, external spermatic fascia, fascia lata grafts, buc-
cal mucosal onlay grafts, fibrin and other synthetic tissue
adhesives, dermal regenerative sheets, etc. However, the
utility and advantage of one over the other have not been
established till date. Beyond local availability, the choice of
waterproofing layers is largely dependent upon the surgeons’
expertise and comfort.
The current systematic review and meta-analysis is an
attempt to summarize the available evidence and to quanti-
tatively evaluate the global results of different waterproofing
layers in substantiating the UCF repair.
Material andmethods
The review was conducted in accordance with the Preferred
Reporting Items for Systematic Reviews and Meta-analy-
ses (PRISMA). The study methods including the review
question, search strategy, inclusion criteria for studies,
data extraction performa and the statistical methods to be
deployed were outlined in advance.
The reviewing team included experts in hypospadiology,
systematic reviews and meta-analysis, epidemiology,biosta-
tisticsand data science. None of the authors had any conflict
of interest.
Inclusion andexclusion criteria forstudies
Primary research on the results of post-hypospadias UCF
repair with or without the use of different waterproofing
layers published in peer-reviewed journals 2000 onwards
was included for analysis. Comments, reviews, editorials
and letters to editors have been excluded. Preliminarily, the
search was not skirted with age- or language-based restric-
tions subject to google-translation (https:// trans late. google.
co. in) facilitated data-extraction.
The presence of another review on the same topic was
excluded prior to undertaking this project. All searches,
screening of titles and abstracts and study selection were
conducted and documented independently by two investi-
gators (in duplicate) and the results were collated. Any dis-
crepancy was resolved by verification with the records and
with the literature. If needed, a consensus was arrived at in
the presence of a third expert.
Search strategy
PUBMED/ PUBMED Central/ PMC databases and Embase
were interrogated primarily with the search terms hypospa-
dias, urethral fistula, urethrocutaneous fistula, dartos, tunica
vaginalis, cover, flap, and glue. The Boolean operators used
were 'AND' and 'OR'. The search results were expanded by
including results delivered by running similar searches on
Google Scholar and Google search engine. Missing arti-
cles were retrieved through reference and citation tracking.
The search strategy and results have been outlined in the
PRISMA flow-diagram (Fig.1). All efforts were undertaken
to exclude publications on UCFs unrelated to hypospadias
repair.
Data extraction
Data were extracted by two reviewers independently using
Microsoft Excel (version 2022). A few publications pre-
sented mixed data on different procedures performed on the
penis or results pertaining to different etiologies of UCF.
Data pertaining to post-hypospadias UCFs was retrieved
subject to the availability of information in the manuscript.
Any discrepancies among the reviewers were resolved by
consensus in the presence of the senior author. A total of
seventy-three included studies were reviewed and analyzed.
The methodological quality of each included study was
assessed with the Joanna Briggs Checklist (JBI) critical
appraisal tools (Supplement Table1).
Statistical analysis
Preliminary analysis was done using the formula function in
Microsoft Excel. The data were then pasted into the MedCalc®
Statistical Software version 20.106 (MedCalc Software Ltd,
Ostend, Belgium; https:// www. medca lc. org; 2022) for sin-
gle-arm meta-analysis. Random effects model was used and
pooled analysis was performed with estimation of the 95%

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confidence interval (CI). Heterogeneity (I2) was tested across
the studies included in the review. The forest plot was drawn
for the entire dataset as well as individually for the different
waterproofing layers. Publication bias was performed by draw-
ing the funnel plot and conducting Begg’s test and Egger’s
test. The results of UCF repair with the use of different water-
proofing layers were compared with the help of two samples
independent proportions test (http:// www2. psych. purdue. edu/
~gfran cis/ calcu lators/ propo rtion_ test_ two_ sample. shtml).
Results
Based on the search strategy, the inclusion and exclusion
criteria, 73 studies relevant to this synthesis were iden-
tified [1–73]. An outline of all the included studies has
been provided in Supplement Table2. Data could not be
extracted from 2 studies; the final analysis is based on 71
studies. The total cohort size is 2886 with 539 (18.7%)
reported failed UCF repairs irrespective of the technique
used. Nearly one-third (23 of 72) of studies have reported
absolute success. Ambriz-González etal. [51] have sug-
gested that the mean number of surgeries per patient in
the surgical group were 3.2 (n = 25) with success in 17
patients, signifying that out of 80 surgeries for UCF clo-
sure, only 17 were a success which is probably the lowest
success reported in the series (21.3%). With such extreme
surgical results, this limb of the study has not been con-
sidered in the analysis.
Most of the studies have provided data pertaining to
the number of patients treated/ success or failure. Forty
percent of the included studies have provided additional
(25 of 72) or exclusive (4 of 72) data sets to understand
the final outcomes in terms of number of UCFs treated.
Databases Interrogated: PUBMED/ PUBMED Central/ PMC databases, Embase
followed by Google Scholar/ Google search engine
Search Terms: hypospadias, urethrocutaneous fistula,urethral fistula, dartos,
tunica vaginalis, cover, flap, glue (all related terms)
Records idenfied: (n = 1272)
* PubMed: (n=449)
* Embase: (n=700)
* Google scholar: (n=123)
Records removed before screening:
* Duplicate records removed (n=312)
* Records removed for other reasons (n=0)
Records screened
(n=960)
Records excluded based upon tle and abstract
screening (n=881)
Reports sought for retrieval (n = 79)
* All could be retrieved
* All assessed for eligibility based upon full-text screening
Reports eclded
* Review arcles, lack of data in arcles, lack of
data specific to UCF closure, UCF not related to
hypospadias repair, language not translatable, etc
(n=27)
Reference search and citaon tracking (n=21)
Studies included in review (n = 73)
noitacifitnedIdedulcnIScreeningEligibility
xu :
Fig. 1 PRISMA flow-diagram

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The study design isn’t clear in all the studies; at least 16
studies are prospective and 29 retrospective. Twenty-five
studies have not provided any information about the type of
hypospadias or the surgeries undergone by the patients con-
stituting the cohort. Thirty-seven studies have preferred to
delay the UCF repair by at least 6months after the last sur-
gery of which six authors have preferred to delay the repair
by one year or more; thirty-two studies have not commented
upon the time interval prior to UCF closure.
UCF repair has been performed over a catheter or a stent
in the majority of the studies. However, intra-operative/
overnight catheterization was preferred by Ehle etal. [3]
(second stage of Cecil Culp repair), Santangelo etal. [10]
(for simple repair), Malone etal. [22] and Kranz etal. [59]
(PATIO repair) and Dekalo etal. [66]. The use of supra-
pubic route has been described alone or in conjunction with
a urinary catheter in seven studies [2, 8, 19, 35, 42, 55, 62].
The authors were interested in studying the use of local or
parenteral testosterone prior to UCF repair, in the absence of
a standard reporting format, such information was lacking.
The use of operating loupes or operating microscopes has
been described in at least 18 studies. The most commonly
used suture material for repair of the urethral rent is polydi-
oxanone or vicryl in sizes 6-0 or 7-0. The reporting of com-
plications was highly heterogenous with most of the authors
either abstaining from or making a blanket statement, “no
intra- or post-operative complications.
The choice of waterproofing layers is influenced by sev-
eral patient factors such as the number, location and size of
UCF, time lag after the last procedure, presence of concomi-
tant meatal stenosis, urethral stricture or other anomalies of
the urethra, availability of local tissues, surgeon’s comfort,
etc. It was observed across multiple studies that generally,
the UCF ≤ 2mm were considered tiny; if solitary, generally
they could be managed with a local repair. UCFs < 4mm
were labelled as small by certain authors while others con-
sidered the cut-off at 5mm. Large, multiple or recurrent
UCFs especially when associated with local scarring or
tissue scarcity were considered notorious. The results of
different barriers used in the included studies have been
summarized in Table1 and the corresponding forest plot is
depicted in Fig.2a.
Early, acute UCF was treated successfully in 2/2 patients
by catheterization and approximation of skin edges with
adhesive strips [1]. Successful resolution (4 of 4; 100%) of
‘pin-point’ fistula soon after TIPS for anterior penile hypo-
spadias with urethral catheterization for 5–7days has also
been reported by [2].
Simple primary closure of UCF with no waterproofing
layer has been reported in 7 studies comprising 12.7% (366
of 2886) patient-strength constituting the pooled cohort
(Table2, Fig.2b). The reported success in the absence of
water-proofing layers is 73.2% (268 of 366; 73.2%). It was
not the exclusive technique for surgical repair of UCFs in
either of these studies; rather it was used as a control to other
techniques [5, 9, 27, 44, 47] or for a specific sub-group of
UCFs: small or pin-point UCFs [1, 39].
The most common tissue (46.7% of the cases) used for
interposition between the urethral repair and the skin is
the dartos or subcutaneous tissue (1347 of 2886 or 46.7%
patients; in 34 studies) with a reported cumulative success of
78.8% (1062 of 1347) (Table3, Fig.2c). Local subcutaneous
Table 1 Comparison of different barrier methods used in the included studies
Study Samplesize Success Proportion (%) 95% CI Weight (%)
Random
Catheterization 2 2 100 15.811–100.000 2.53
Simple primary closure 366 268 73.224 68.375–77.693 15.28
Dartos 1347 1062 78.842 76.562–80.995 15.76
Tunica Vaginalis 299 282 94.314 91.053–96.653 15.14
PATIO 46 43 93.478 82.104–98.634 11.91
Dermal substitutes 38 35 92.105 78.623–98.341 11.33
Bio-adhesives 69 39 56.522 44.042–68.424 12.99
Skin-based flaps 272 238 87.5 82.973–91.186 15.06
Total (random effects) 2439 83.455 75.565–90.060 100
Test for heterogeneity
Q106.3295
DF 7
Significancelevel P < 0.0001
I2 (inconsistency) 93.42%
95% CI for I289.30–95.95

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tissue or dartos is inevitably a component of additional 272
cases (from 8 studies) also wherein skin-based flaps were
used (total 1624/2898 or 56%) with a success at 79.5%
(1212/1522 in 44 studies).
Of the 34 studies included in the dartos group, 7 studies
[20, 32, 38, 42, 48, 69, 72] have concentrated largely on
primary UCF (first surgery for UCF repair) with 73.9% suc-
cess (75/287 failures). There were 6 studies evaluating the
results of UCF closure on cases with one or more prior failed
repairs; the success rate was 74.4% (29/39 in five studies).
However, the majority of the studies (n = 14) have a mixed
cohort with both primary and recurrent cases of UCF closure
with a success rate of 78.9% (failures: 176/833; 14 studies).
Scrotal flaps have been utilized in five studies either as a
simple flap of scrotal dartos [5, 26, 28] or a tongue-shaped
flap that was flipped [18] or a scrotal septal vascular pedicle
flap [50]. Success with the scrotal tissues has been reported
at 94.6% (failure 4/74). Scrotal vascular pedicle flaps based
on anterior and posterior scrotal vessels yielded absolute
success (29/29) when used to repair UCF as large as 1–2cm.
Soni etal. flipped a tongue-shaped tissue of scrotal dartos
in 23 patients; all UCF were ≥ 4mm in the series and there
was only 1 failure (1/29).
The use of double dartos flaps mobilized from opposite
directions and drawn across the repair/ overlapped with
each other has been documented in eight studies [2, 7, 24,
28, 34, 42, 46, 48, 55, 61] with a cumulative success of
81% (322/398). Ajape etal. [55] added a double-slit to the
dartos flap on the dorsal aspect of the penis to release the
tension in 11 patients with success in 9 (81.2%). Dartos
has been used as a ‘flip-flap’ in two studies with 90% suc-
cess (27/30) [30, 36]. Dartos has also been used as a de-
epithelialized turn-over dartos flap with absolute success
[20] and scrotal septal vascular pedicle flaps [50]. Ajape
etal. double-breasted the dartos ventrally at the cost of the
dorsal slit (9/11; 81.8%) [55]
The use of tunica vaginalis (flap or graft) has been
reported in 319 of 2886 cases (11%) in 18 of 72 stud-
ies (25%) (Table4, Fig.2d). Results specific to the use
of tunica vaginalis could not be segregated in two stud-
ies [4, 26]. The success rate of tunica vaginalis is 94.3%
(282/299; 16 studies). Of these, Aldaqadossi etal. [65]
have studied the role of tunica vaginalis free graft with
a reported success of 95.5% while Xie'eryazidan etal.
[27] have studied the role of tunica vaginalis flap with
spermatic fascia (success 84.6%). 10 of 18 studies have
reported nil failure after the use of tunica vaginalis flap.
It was observed that 50% (9 of 18) studies on the use of
tunica vaginalis were published during a time-frame of
5years (2008–13).
PATIO repair (Preserve the Tract and Turn it Inside Out)
has been deployed in 4 studies [22, 33, 53, 59] with a docu-
mented success rate of 93.5% (43 of 46). The procedure was
considered appropriate for UCFs < 4mm by both Nerli etal.
and Rathod etal. [33, 53].
The use of buccal mucosal onlay graft for repair of UCF
has been described in 47 patients (in 5 studies). Failure of
UCF closure after buccal mucosal graft was observed in
17% (8/47). The onlay graft was protected by dartos in 3
studies [25, 52, 70] while Kiss etal. used no waterproofing
Table 2 Comparative analysis of different studies evaluating the success of simple primary closure (no waterproofing layer) in UCF closure
Study Samplesize Success Proportion (%) 95% CI Weight (%)
Random
Latifoglu etal. 2000 133 109 81.955 74.351–88.083 22.12
Shankar etal. 2002 76 49 64.474 52.659–75.123 19.47
Cimador etal. 2003 49 37 75.51 61.130–86.657 16.9
Xie'eryazidan etal. 2009 20 11 55 31.528–76.942 11.11
Yasin etal. 2011 10 5 50 18.709–81.291 7.23
Qin etal. 2012 74 55 74.324 62.844–83.780 19.32
Neilson etal. 2013 4 2 50 6.759–93.241 3.85
Total (random effects) 366 69.667 60.843–77.814 100
Test for heterogeneity
Q15.4536
DF 6
Significancelevel P = 0.0170
I2 (inconsistency) 61.17%
95% CI for I211.25–83.02

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layer between the flap and the skin [12]. The four cases in
the series by Sarayreh etal. were (possibly) protected by
rotational or advancement skin flaps [42]. The size of UCF
was > 4mm for 35/46 patients; the source of graft was inner
cheek or lower lip.
The use of biomaterials or dermal substitutes has been
described in 4 studies [41, 61, 64, 68] with a cumulative suc-
cess of more than 92% (35/38). Procine etal. used Pelvicol
or porcine acellular dermal collagen matrix (allogenic graft
material) while Naderi used dCELL or cadaveric, decel-
lularized, human dermal matrix produced from split-skin
grafts; both have documented absolute success (no failures).
Pelvicol had to be removed piece-meal in one patient with
refractory infection although there was no recurrence of
UCF. Casal-Beloy etal. have published their experiences
with the use of a monolayer dermal (bovine) skin regenera-
tion sheet [63].
The results of the use of biocompatible adhesives have
been described in 6 studies [6, 29, 35, 43, 51, 69]. Two
studies have reported absolute success; both of them have
used fibrin; one of them is a case-report. The success rate
with the use of tissue glue is 56.5% (39/69). Tissue glue
has been used for repair of early fistula (soon after catheter
removal) in at least 14 cases with successful resolution in
9. Lapointe etal. and Ambriz-Gonzalez etal. have applied
triamcinolone cream locally for 2–3days before glue appli-
cation to decrease the inflammatory response and oedema.
Multiple layers of glue were subsequently applied to the
UCF site. Tawfeeq etal. sandwiched the glue between the
urethral repair and the dartos flap while Kajbafzadeh etal.
sandwiched a dartos flap between a layer of glue on either
side. Prestipino etal. observed that the UCF most likely
to respond were the ones which responded to the very first
application. Three of these studies have been published
within the last 5years.
Several skin-based flaps have been described in the
included reports [1, 2, 5, 9, 10, 15, 38, 58] including the
layered closure in the pant-over-vest technique, rotation/
advancement/transposition flaps, de-epithelialized skin flaps
and the split-onlay two-layered skin flap. The overall success
Fig. 2 A Forest Plot to depict the comparison of different barrier
methods used in the included studies. B Forest plot to depict the
results of UCF closure in different studies evaluating the success of
simple primary closure (no waterproofing layer). C Forest plot to
depict the results of UCF closure in different studies evaluating the
success of dartos flap (lines from top to bottom in order: Abdullaev
etal. [72], Ahuja etal. 2008, Ajape and Kuranga [55], Aldaqadossi
etal. [65], Awad [16], Choi etal. [46], Dekalo etal. [66], Elbakry [2],
Han etal. 2017, Jamal etal. 2010, Jozsa etal. 2011, Karakus et al.
2013, 2016, Latifoglu etal. 2000, Mohamed etal. [30], Muruganand-
ham etal. [28], Neilson and Nicholls [47], Ozturk [31], Sahin etal.
[13], Sarayreh [42], Shahzad etal. [36], Shankar etal. [5], Sharma
et al. [45], Shaw et al. [71], Shehata [24], Shirazi et al. [54], Soni
and Sheoran [18], Srivastava etal. [38], Tawfeeq etal. (AJU) 2021,
Waterman etal. [7], Yasin etal. 2011, Yilmaz etal. 2017, Zhou etal.
[50]). D Forest plot to depict the results of UCF closure in different
studies evaluating the success of tunica vaginalis. E Funnel plot of
the included studies

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Table 3 Comparative analysis of different studies evaluating the success of dartos flap in UCF closure
Study Sample size Success 95% CI Weight (%)
Random
Abdullaev etal. 2021 19 17 66.862–98.699 2.63
Abdullaev etal. 2021 33 26 61.092–91.020 2.96
Ahuja etal. 2008 10 10 69.150–100.000 2.15
Ajape etal. 2016 11 9 48.224–97.717 2.22
Aldaqadossi etal. 2020 2 2 15.811–100.000 1.03
Awad etal. 2005 32 31 83.783–99.921 2.95
Choi etal. 2013 7 7 59.038–100.000 1.86
Dekalo etal. 2020 81 64 68.537–87.272 3.31
Elbakry etal. 2001 42 30 55.416–84.281 3.08
Han etal. 2017 182 121 59.124–73.296 3.47
Jamal etal. 2010 11 11 71.509–100.000 2.22
Jozsa etal. 2011 8 8 63.058–100.000 1.97
Karakus etal. 2013 15 13 59.540–98.342 2.46
Karakus etal. 2013 2 2 15.811–100.000 1.03
Karakus etal. 2016 14 13 66.132–99.819 2.41
Latifoglu etal. 2000 45 39 73.208–94.946 3.11
Mohamed etal. 2010 19 18 73.972–99.867 2.63
Muruganandham etal. 2010 17 13 50.101–93.189 2.55
Muruganandham etal. 2010 21 19 69.623–98.825 2.7
Neilson etal. 2013 20 20 83.157–100.000 2.66
Ozturk etal. 2010 6 6 54.074–100.000 1.74
Sahin etal. 2003 32 30 79.193–99.234 2.95
Sarayreh etal. 2012 98 87 80.803–94.262 3.36
Sarayreh etal. 2012 62 20 20.940–45.336 3.23
Shahzad etal. 2011 11 9 48.224–97.717 2.22
Shankar etal. 2002 113 80 61.499–78.971 3.39
Shankar etal. 2002 1 0 0.000–97.500 0.76
Sharma etal. 2013 18 9 26.019–73.981 2.59
Shaw etal. 2021 10 10 69.150–100.000 2.15
Shehata etal. 2009 4 3 19.412–99.369 1.44
Shehata etal. 2009 7 7 59.038–100.000 1.86
Shirazi etal. 2016 40 39 86.841–99.937 3.06
Soni etal. 2007 23 22 78.051–99.890 2.75
Srivastava etal. 2011 16 11 41.338–88.983 2.51
Srivastava etal. 2011 3 3 29.240–100.000 1.26
Tawfeeq etal. (AJU) 2021 20 14 45.721–88.107 2.66
Waterman etal. 2002 161 117 65.099–79.388 3.46
Yasin etal. 2011 57 51 78.484–96.038 3.2
Yilmaz etal. 2017 45 42 81.732–98.603 3.11
Zhou etal. 2014 29 29 88.056–100.000 2.89
Total (random effects) 1347 80.126–89.734 100
Test for heterogeneity
Q212.5337
DF 39
Significancelevel P < 0.0001
I2 (inconsistency) 81.65%
95% CI for I275.71–86.14

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165 Page 8 of 12
with these flaps is 87.5% (failures: 34/272). The rates of suc-
cess within the techniques are highly variable from 54.5%
(6/11; Patel etal.) with the split onlay (two-layered) skin flap
to 100% (20/20; Gite etal.) with the use of de-epithelialized
flap (pant-over-vest) technique. Most (6/8) reports have been
published within the time-frame 2000–2005.
The publication bias has been assessed through the funnel
plot and Egger’s and Begg’s tests (Fig.2e).
Several techniques have been described in solitary
reports. Ochi etal. have described the use of pedicled
external spermatic fascia with absolute success (100%)
in 26 patients [49]. The use of fascia lata-free grafts has
been described by Kargi etal. in 8 patients with 9 UCF and
no recurrence [11]. The two-staged Cecil Culp repair was
described by Ehle etal. with no recurrence in a series of 15
patients [3]. Chen etal. described the use of release incisions
in penile skin lateral to the suture line with no failure in 34
cases constituting the cohort [73]. The only failures reported
in innovative yet anecdotal techniques include 1 (1/27) in the
series by Qin etal. with their prepuce degloving technique
[44] and 1 with the tube grafts (1/6) described by Latifoglu
etal. [1].
Discussion
The wide variety of techniques described to repair the UCF
and the utilization of almost all feasible tissues simply indi-
cates that no single technique or tissue is perfectly suited to
repair all varieties of fistula; the same assertion is applicable
to the primary repair of hypospadias as well. The param-
eters reported across various studies are highly heterogenous
with different authors focusing on different aspects of the
procedure.
The results with the use of double dartos flaps (81%;
322/398) are not superior to that of single dartos flaps
(78%; 740/949) (p = 0.230). The single dartos, moreover,
is more frequently used in view of simplicity, tissue avail-
ability and ease of dissection. Shehata etal. [24] operated
on 11 patients; 4 patients were provided with a single layer
of dartos while 7 were repaired with double dartos layers.
One patient who had been repaired with a single dartos layer
developed a recurrence of UCF while all those who were
repaired with double dartos did well.
The scrotal dartos yields superior results than the penile
dartos or local subcutaneous tissue (scrotal dartos: 70/74,
penile dartos: 992/1273; p = 0.001). This may be related to
multiple factors. The penile dartos or subcutaneous is con-
sumed, scarred or devascularized after multiple surgeries.
Surgical dissection during UCF closure is detrimental to the
local vascularity thereby comprising its viability as a water-
proofing layer. Scrotal dartos is abundant in volume, mostly
virgin has a rich blood supply and reserved the capability to
be flipped over a considerable length of the penis. The scro-
tal skin has enormous distensibility and the scrotum may be
reconstructed post-harvest without disfigurement, the lanugo
hair is a problem though. Zhou etal. [50] have demonstrated
the mobilization of the scrotal septal vascular pedicle flaps
based on anterior and posterior scrotal arteries and their
anastomotic branch for three-layered reconstruction with 0
failures in a series of 29. The posterior scrotal artery is an
off-shoot of the internal pudendal artery while the anterior
scrotal artery is an off-shoot of the external pudendal artery.
The use of tunica vaginalis is associated with results
much superior to those with the dartos flap (1062/1347 vs
282/299; p = 0.000). TVF is highly vascular, thin and pli-
able. The blood supply to the tunica vaginalis arises from
the cremateric vessels. It is universally available around both
the testes, sufficient in quantity, technically simple to har-
vest and abundant enough to be tunneled to the distal penile
region. The use of TVF was initially described for Peyronie’s
disease and chordee correction [64]. The incorporation of
cremasteric fibers into the TVF may, however, lead to penile
curvature which might be severe enough to warrant surgical
division. The use of tunica vaginalis flap was first described
by Hosli etal.; the use was popularized by Snow etal. [65].
He used a blanket TVF wrap on the penis after hypospadias
repair. The use of tunica vaginalis graft for the repair of
UCF was described by Voges etal. There was no difference
in outcomes between the use of tunica vaginalis flap or graft
(239/254 vs 43/45; p = 0.696).
PATIO repair compares favorably with the use of dartos
flaps (43/46 vs 1062/1347; p = 0.016) but not with tunica
vaginalis flap (43/46 vs 282/299; p = 0.821). The fistula
tract needs to be dissected without injury and is inverted
into the urethral lumen with its mouth directed away from
the urinary stream. The procedure is simple yet the surgeon
needs to be meticulous. However, it reduces the operating
time, hospital stay, morbidity and patient discomfort [33].
The procedure has been described to avoid the use of water-
proofing layers; yet the possibility of additional maneuvers
or waterproofing layers is not mandatorily precluded. Nerli
etal. chose to protect the urethral suture line with a layer
of TVF when the UCF was larger (2–4mm). Rathod etal.
modified the procedure by applying a purse-string suture to
the fistula tract prior to inverting it.
Buccal mucosal onlay graft scored equivalent to the use of
dartos flaps (p = 0.494) as well as PATIO repair (p = 0.117);
yet it was inferior to the tunica vaginalis flap (0.005266).
The buccal mucosa has a thick epithelial layer but a thin
lamina propria; the histological property confers mechanical
stiffness to the tissue and makes it easy to handle. It is elastic
and less contractile post-graft. The lamina propria is thin and
allows imbibition from the recipient bed; the highly vascular
lamina propria also facilitates inosculation. It has a natural
inherent barrier to local sepsis [69]. The most common site

Pediatric Surgery International (2023) 39:165
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Page 9 of 12 165
of harvesting is the inner cheek followed by the inner lower
lip in view of its thickness. Besides, the lip offers a lim-
ited size of the graft due to its anatomic predisposition. The
possibility of lip contracture is another consideration; the
complication has been described in only 3–5% of the cases.
The use of biomaterials or dermal substitutes is associ-
ated with results superior to that of dartos flaps (p = 0.047)
but not to those of tunica vaginalis (p = 0.587), PATIO
(p = 0.808) or buccal mucosa (p = 0.213). These matrices
are strong yet flexible and free of cellular content (including
DNA) and non-allergenic. They splint the urethral repair
temporarily and facilitate the laminar flow of urine. The use
of tissue glues has gained momentum in the last few years.
They belong to the cyanoacrylate group of adhesives which
bond strongly with a variety of substances in presence of
blood and body fluids. Isobutyl 2-cyanoacrylate, isoamyl
2-cyanoacrylate, and 2-octyl cyanoacrylate and non-toxic
and used in medicine. Although the projected results are
inferior to all the techniques described previously, yet they
offer the potential to avoid both general anesthesia and sur-
gery. Besides, the low cost and feasibility of repeated appli-
cations are yet other factors that make them popular.
The de-epithelialized skin flap technique was described by
Szymanowski etal. [74]. The use of de-epithelialized flaps in
hypospadias repair for urethral reconstruction was introduced
by Smith in 1973 [74]. The de-epithelialized skin flaps in a
pant-over-vest technique have scored superior to dartos flaps
(p = 0.001) and the bio-compatible adhesives (p = 0.000) but
the results are not significantly different from those of PATIO
(p = 0.242), buccal mucosal onlay graft (p = 0.397) and der-
mal substitutes (p = 0.412092). The tunica vaginalis scored
superior to the de-epithelialized flaps (p = 0.004).
One of the multiple concerns while repairing the UCF
is not to create any narrowing of the urethral lumen at the
site of repair. As per Bernoulli’s principle, when fluid flows
into a narrower channel, its speed or its kinetic energy
increases. Similar mechanisms inside the urethra which has
been repaired recently and is still healing may predispose to
breakdown. The Snodgrass principle is technically simple
and serves to relieve tension on the suture line at the cost of
a dorsal midline incision in the urethral wall. It has been uti-
lized globally during TIPS urethroplasty for distal, mid-shaft
and even proximal hypospadias repairs. The same principle
was extrapolated to UCF repair and its utility demonstrated
Table 4 Comparative analysis of different studies evaluating the success of tunica vaginalis in UCF closure
Study Sample size Success Proportion (%) 95% CI Weight (%)
Random
Aldaqadossi etal. 2020 45 43 95.556 84.851–99.457 8.88
Bhat etal. 2019 32 30 93.75 79.193–99.234 8.11
Kadian etal. 2011 14 13 92.857 66.132–99.819 5.93
Landau etal. 2003 14 14 100 76.836–100.000 5.93
Mohamed etal. 2010 16 16 100 79.409–100.000 6.29
Muruganandham etal. 2010 13 13 100 75.295–100.000 5.73
Nerli etal. 2011 4 4 100 39.764–100.000 2.98
Ochi etal. 2014 9 9 100 66.373–100.000 4.75
Pescheloche etal. 2018 36 36 100 90.261–100.000 8.39
Routh etal. 2006 16 16 100 79.409–100.000 6.29
Routh etal. 2008 22 22 100 84.563–100.000 7.16
Shankar etal. 2002 5 1 20 0.505–71.642 3.41
Sharma etal. 2013 20 16 80 56.339–94.267 6.9
Singh etal. 2004 14 14 100 76.836–100.000 5.93
Srivastava etal. 2011 13 13 100 75.295–100.000 5.73
Xie'eryazidan etal. 2009 26 22 84.615 65.132–95.644 7.59
Total (random effects) 299 94.421 89.735–97.744 100
Tests for heterogeneity
Q34.7923
DF 15
Significancelevel P = 0.0026
I2 (inconsistency) 56.89%
95% CI for I224.69–75.32

Pediatric Surgery International (2023) 39:165
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165 Page 10 of 12
by 5 studies in the series [16, 24, 30, 48, 71]. Interestingly,
dartos was used as the waterproofing layer in all five stud-
ies. The success rate with the use of TIPS principle is 94.3%
(82/87) vis-à-vis 77.8% (980/1260) without the use of TIPS
(p = 0.000). The dorsal slit should be deep enough to permit
tension-free approximation of the urethral edges at the site
of UCF. However, it must be borne in mind that injury to the
underlying corpora will not only cause troublesome bleed-
ing, but it will also heal with local scarring.
Several techniques have been reported in solitary reports;
they were clubbed together to form a miscellaneous group.
It might be interesting to contemplate why such techniques
were not evaluated by others especially in the scenario when
we are still looking for a perfect solution.
The following protocols were observed across an over-
whelming majority if not all the studies: (a) pre-operative
assessment of size, site and number of UCFs as well as
the availability/quality of local tissues, (b) identification
of all urethrocutaneous fistula by occluding the urethra at
the penoscrotal junction with a tourniquet and inflating the
urethra with either xylocaine jelly (practiced in the authors’
institution), methylene blue, betadine or iodine, (c) exclude
the presence of any obstruction distal to the UCF including
the presence of meatal stenosis with the help of a urethral
sound (this may also be done in the pre-operative period
by routine calibration); presence of such obstruction shifts
the priority from UCF closure to addressing the stricture,
(d) freshening the edges of the UCF, (e) applying invert-
ing sutures to bury the mucosal edges inside the repair, (f)
use of optical magnification (loupes are preferred over the
operating microscopy) for better visualization, (g) use of
fine suture material, preferably 5-0 or 6-0 PDS or vicryl, (h)
avoiding overlapping suture lines, (i) provision for a water-
proofing layer between the urethral repair and the overlying
skin, (j) use of urinary catheter as a stent for urethral repair
and to keep the suture line dry by diverting the stream of
urine and (k) ensuring a time interval of at least 6months
after the last surgery to allow time for inflammation and
edema to settle as well as for neo-vascularization.
A list of factors identified as unfavorable for the healing
of UCF repair across different studies was prepared during
data extraction. Those highlighted frequently and promi-
nently include the poor quality of local tissues including thin
and fragile skin or local scarring or residual edema, traction
effect of erection in the post-operative period especially for
coronal repairs, fecal contamination of the surgical site due
to genital proximity to the anal opening, diminished blood
flow to local tissues in view of previous surgeries, incorrect
or inappropriate suture techniques such as failure to invert
the urethral mucosa, use of non-absorbable suture material,
poorly designed flaps, overlapping of suture lines or failure
to add a second layer, sutures placed into the urethra, hema-
toma formation within the dead spaces at the surgical site,
devitalization of tissue due to dissection and technical fac-
tors such as failure to free the urethra tissues from the penile
skin or a compromise of the urethral lumen.
The synthesis is limited by the quality and the informa-
tion available in the included studies. Every case of hypo-
spadias is different and the technique has to be customized to
the needs of the patient. Moreover, it is not just the patients,
different surgeons have different levels of technical exper-
tise which may vary for different surgical procedures. The
third element is introduced by the different pre-, intra- and
post-operative protocols such as time gap after the last sur-
gery, use of testosterone, urinary catheter (stented vs non-
stented repair, size and material, duration of catheteriza-
tion, etc.), suture material and suturing technique, choice
of water-proofing layer, etc. With a large number of factors
working in unison, each influencing the outcomes indepen-
dently as well as in conjunction with the other variables, it
is extremely difficult to quantify the individual roles of the
different waterproofing layers. The heterogeneity of informa-
tion divulged in the absence of a universal reporting format
is yet another limitation.
Conclusions
A plethora of options is available for use as a waterproofing
layer after the repair of UCF. Although the tunica vaginalis
offers the best results after UCF closure in the synthesis,
almost all popular waterproofing layers and surgical tech-
niques have depicted absolute (100%) success in the hands
of one or more surgeons. Hence, the choice of layer alone
is not the only consideration. There are a vast number of
factors (patient’s local anatomy, surgeon’s expertise and
technical perspectives) that influence the final outcome.
Summarily, it is not possible to label any technique as ideal
or perfect.
Supplementary Information The online version contains supplemen-
tary material available at https:// doi. org/ 10. 1007/ s00383- 023- 05405-1.
Author contributions Concept: PGData Search: PG, PC, KS, VJ, DKY,
SMData Extraction: PG, PC, KS, AD, SK, SMData Analysis: PC, VV,
PG, SAManuscript drafting: PG, PCManuscript review: MB, SKA, RS
Funding Indian Council of Medical Research, India (Grant nos.
5/4/7-1/Uro/2020-NCD-II, 5/4/7-1/Uro/2020-NCD-II).
Data Availability Being a systematic review & meta-analysis, the whole
data pertaining to this study is already in public domain.
Declarations
Competing interests The authors declare no competing interests.

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