Factors associated with reoperation in hypospadias surgery — A nationwide, population-based study

Summary

Background/Objective

To analyze the preoperative factors associated with the need for secondary surgery following primary urethroplasty.

Methods

This study utilized a subset of the National Health Insurance Research Database, which includes the data on all paid medical benefit claims from 1997 to 2007, for 1 million beneficiaries in 2005. We analyzed the claims data for all patients with hypospadias who had undergone primary urethroplasty. The characteristics of the patients, surgeons, and hospitals associated with surgical outcomes were analyzed to investigate possible associations with the need for secondary surgery.

Results

Among 52,705 live male newborn babies, 218 were diagnosed with hypospadias, of whom 89 received repair surgery. A total of 75 (84.3%) male newborn babies received single hypospadias surgery, and 14 (15.7%) underwent more than two surgical procedures. Univariate analysis demonstrated that the type of hypospadias and the surgeon caseload volume were significantly associated with the need for additional hypospadias surgery (p = 0.02 and p = 0.03, respectively). In multivariate analysis, the type of hypospadias (distal vs. proximal, odds ratio, 0.25; p = 0.03) and the surgeon caseload volume (high vs. low, odds ratio, 0.04; p = 0.05) were significantly correlated with secondary operation.

Conclusion

The type of hypospadias and the surgeon caseload volume were significantly associated with the need for secondary hypospadias surgery. The findings of this study provide important information on the outcomes of hypospadias repair for parents and specialists.

Keywords

complications;hypospadias;reoperation;surgeon volume;urethroplasty

1. Introduction

Hypospadias, a condition marked by an abnormal ventral urethral meatus, an incompletely developed prepuce, and abnormal ventral penile curvature, is a frequent congenital malformation in male newborn babies.^{1 ;  2} In spite of considerable advances in surgical techniques, a number of patients experience complications and may require multiple surgeries. Common complications that require a secondary surgery include urethral stricture, persistent hypospadias, urethrocutaneous fistulae, diverticula, urethral calculi, obstruction from hair-bearing skin used in previous repair, and chordee.³ The experience of the surgeon and patient age are strongly associated with outcomes.^{4 ;  5} Significant risk factors requiring reoperation are penoscrotal or proximal shaft hypospadias, a lack of neourethral vascular tissue coverage, and patient age above 4 years.⁶

Previous studies on hypospadias outcomes have been from single-center series or small multi-institutional series with highly experienced surgeons,⁷ and a population-based analysis of secondary surgery after hypospadias repair is still lacking. In the present study, we aimed to investigate the factors associated with reoperation in hypospadias surgery by analyzing data from the National Health Insurance Research Database (NHIRD) in Taiwan.

2. Methods

2.1. Data source

2.1.1. NHIRD

This study utilized data from the NHIRD, which is provided by the Bureau of National Health Insurance (NHI), Department of Health, Taiwan, and managed by the National Health Research Institutes, Taiwan. As of 2005, the NHI program covers nearly 99% of the population of Taiwan, and the NHI registry of beneficiaries (individuals enrolled during all or any part of the year 2005) numbers 22.72 million. The NHIRD includes a registry for contracted medical facilities, another for board-certified specialists, a monthly summary of inpatient claims, and details of inpatient orders and principal operational procedures. The NHI has collected claim records covering all paid inpatient and outpatient medical benefit claims for the entire population of Taiwan from the inception of its program in 1995, and the National Health Research Institutes makes considerable data available for research. The entire data collection is known as the NHIRD.

2.1.2. Longitudinal Health Insurance Database 2005

The present study utilized a subset of the NHIRD known as the Longitudinal Health Insurance Database (LHID) 2005, which contains all inpatient and outpatient medical benefit claims from 1997 to 2007 for a sample of one million beneficiaries randomly drawn from the total number of individuals in the NHI Registry of Beneficiaries as of 2005 (individuals enrolled for all or any part of the year 2005). The 1 million de-identified individuals included in the LHID 2005 provide a good statistical representation of the whole population.

2.2. Study sample

The study protocol was approved by the Research Ethics Committee of National Taiwan University Hospital (No. 201004006R). The study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. According to Taiwanese laws concerning the ethics of human subject research and to the formulae of the Institutional Review Board of the National Taiwan University Hospital, Taipei, Taiwan informed consent was not required for this purely retrospective review study. We first selected data from the LHID 2005 on all male babies born alive during the study period, and identified a total of 52,705 newborn babies. Among them, 218 had a claims record, including a diagnosis of hypospadias as defined by code 752.6 (1992 edition) or 752.61 [2001 edition; International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM)]. Eighty-nine of these patients underwent primary repair. The associated congenital anomalies identified by ICD-9-CM codes 740–759 were also analyzed. The primary surgeries included all one-stage procedures for hypospadias and were categorized as repair for proximal and distal hypospadias. The secondary surgeries included minor revision surgeries, such as cystourethroscopy, urethral dilatation, meatotomy, and correction of chordee, and major revision surgeries, such as fistula repair and re-do urethroplasty.

2.3. Key variables of interest

The following variables were included in the analyses.

Patient characteristics included year of surgery, age and comorbidities based on the Charlson comorbidity index, type of surgical procedure codes (distal vs. proximal urethroplasty), associated congenital anomalies, number of previous outpatient clinic visits, number of well-baby clinic visits, geographic location of residence, urbanization level of residence, and insurance fee. The insurance fee of patients without regular-pay work mainly depends on the incomes of parents or guardians.

Hospital characteristics included ownership of the hospital (public, private, or nonprofit), hospital level, and hospital caseload volume. Hospital level indicated whether the hospital was a medical center, regional hospital, district hospital, or private clinic. The hospital level served as a proxy for clinical service capabilities.

Surgeon characteristics included gender, specialty (urology vs. pediatric surgery), age, years since license certification, and caseload volume (the last 3 being surrogates for practical experience).

Surgeon volume was calculated by the number of primary hypospadias surgeries performed by each surgeon during the 11-year study period. The number of procedures performed at each hospital during the study period was calculated as the hospital volume. The hospital and surgeon volumes were then stratified into three categories: low (1–3), medium (4–10), and high (> 10).

2.4. Urbanization level

The 359 municipalities in Taiwan were stratified into eight groups according to the standards published by the National Health Research Institutes, Taiwan, with 1 indicating “most urbanized” and 8 indicating “least urbanized.” These standards included the population density, the proportion of the population with a college education or above, the proportion of the population over 65 years of age, the proportion of agricultural workers in the population, and the number of physicians per 100,000 population.⁸

2.5. Statistical analysis

Statistical analyses were performed using the SAS software (version 9.1; SAS Institute Inc., Cary, NC, USA). Continuous data were expressed as mean (standard deviation) and categorical data as percentages. The Chi-square test or Fishers exact test was used to analyze the categorical data. Multivariate analysis was conducted using a logistic regression model to predict the factors associated with the need for secondary surgery following primary urethroplasty. Two-tailed p < 0.05 was considered statistically significant.

3. Results

The study sample comprised 89 patients who underwent hypospadias repair during the study period. The characteristics of the patients, surgeons, and hospitals and the risk factors associated with the need for secondary surgery are shown in Table 1. Among the 89 patients, 75 (84.3%) received single hypospadias repair, and 14 (15.7%) underwent more than two surgical procedures. Distal hypospadias repair was performed in 50 cases (56.2%), and proximal hypospadias repair in 39 cases (43.8%). The reoperation rate was significantly higher in patients with proximal shaft hypospadias (25.6%) than in those with distal hypospadias (8%). Surgeon caseload volume was significantly associated with the likelihood of hypospadias reoperation. Hypospadias reoperation was not significantly correlated with age at hypospadias surgery, calendar year, household income, urbanization level of residence, or other hospital or surgeon factors.

Table 1. Characteristics of patients, surgeons, and hospitals of 89 subjects who underwent hypospadias surgery.

Variable	Single procedure a	Multiple procedures a	Odds ratio (95% CI)	p
No. of patients	75 (84.3)	14 (15.7)
Patient characteristics
Age (mo)	30.85 ± 24.59	25.64 ± 11.82		0.44
Age (mo)				0.49
< 13	16 (88.9)	2 (11.1)	1.00
13–18	14 (87.5)	2 (12.5)	1.14 (0.14–9.21)
19–24	12 (75.0)	4 (25.0)	2.67 (0.42–17.05)
25–36	13 (81.2)	3 (18.8)	1.85 (0.27–12.76)
37–60	9 (75.0)	3 (25.0)	2.67 (0.37–19.06)
>60	11 (100)	0 (0)	0
Type of hypospadias				0.02
Distal	46 (92.0)	4 (8.0)	1.00
Proximal	29 (74.4)	10 (25.6)	3.97 (1.14–13.8)
Year of surgery				0.13
≤2000	11 (78.6)	3 (21.4)	1.00
2001–2004	32 (78.1)	9 (21.9)	1.03 (0.24–4.51)
≥2005	32 (94.1)	2 (5.9)	0.23 (0.03–1.56)
CCI	0.76 ± 0.71	0.64 ± 0.50		0.56
CCI				0.61
0	28 (84.8)	5 (15.2)	1.00
1	39 (81.3)	9 (18.7)	1.29 (0.39–4.27)
2	6 (100)	0 (0)	0
≥3	2 (100)	0 (0)	0
Household income (NTD)	25,368 ± 4547	24,526 ± 7442		0.57
Insurance fee (NTD)				0.88
<23,000	16 (88.9)	2 (11.1)	1.00
23,000–24,999	24 (85.7)	4 (14.3)	1.33 (0.22–8.16)
25,000–27,499	19 (82.6)	4 (17.4)	1.68 (0.27–10.43)
≥27,500	16 (80.0)	4 (20.0)	2.00 (0.32–12.51)
Other congenital anomalies				0.49
0	43 (89.6)	5 (10.4)	1.00
1	20 (80.0)	5 (20.0)	2.15 (0.56–8.28)
2	9 (75.0)	3 (25.0)	2.87 (0.57–14.22)
≥3	3 (75.0)	1 (25.0)	2.87 (0.25–33.07)
No. of visits to well baby clinic				0.24
<2	40 (88.9)	5 (11.1)	1.00
2–5	31 (77.5)	9 (22.5)	2.32 (0.71–7.63)
≥6	4 (100.0)	0 (0.0)	0
Geographic region of residence				0.79
Central	19 (86.4)	6 (13.6)	1.00
Northern	36 (85.7)	3 (14.3)	1.06 (0.24–4.70)
Southern	20 (80.0)	5 (20.0)	1.58 (0.33–7.56)
Urbanization level of residence				0.48
Urban (1–4)	58 (82.9)	12 (17.1)	1.00
Rural (5–8)	17 (89.5)	2 (10.5)	0.57 (0.12–2.79)
Characteristics of hospital
Level of hospital				0.22
Medical center	48 (80.0)	12 (20.0)	1.00
Regional	18 (90.0)	2 (10.0)	0.44 (0.09–2.18)
Local	9 (100)	0 (0)	0
Hospital ownership				0.65
Public	13 (81.3)	3 (18.7)	1.00
Private nonprofit	58 (84.1)	11 (15.9)	0.82 (0.20–3.37)
Private for–profit	4 (100)	0 (0)	0
Hospital volume				0.29
Low (1–3)	29 (85.3)	5 (14.7)	1.00
Medium (4–10)	23 (76.7)	7 (23.3)	1.77 (0.50–6.30)
High (>10)	23 (92.0)	2 (8.0)	0.50 (0.09–2.84)
Characteristics of surgeon
Age (y)	46.19 ± 7.12	43.14 ± 7.07		0.15
Age (y)				0.39
<40	17 (81.0)	4 (19.0)	1.00
40–44	14 (73.7)	5 (26.3)	1.52 (0.34–6.76)
45–49	15 (83.3)	3 (16.7)	0.85 (0.16–4.43)
50–54	22 (95.7)	1 (4.4)	0.19 (0.02–1.89)
≥55	7 (87.5)	1 (12.5)	0.60 (0.06–6.44)
Years since board certification	10.75 ± 4.80	8.79 ± 3.60		0.15
Years				0.12
<5	9 (90.0)	1 (10.0)	1.00
5–9	19 (76.0)	6 (24.0)	2.84 (0.30–27.25)
10–14	27 (79.4)	7 (20.6)	2.33 (0.25–21.63)
≥15	20 (100.0)	0 (0)	0
Specialty				0.68
Urology	20 (87.0)	3 (13.0)	1.00
Pediatric surgery	55 (83.3)	11 (16.7)	1.33 (0.34–5.28)
Caseload volume				0.03
Low (1–3)	43 (81.1)	10 (18.9)	1.00
Medium (4–10)	20 (83.3)	4 (16.7)	0.86 (0.24–3.08)
High (>10)	12 (100)	0 (0)	0

CCI = Charlson comorbidity index; CI = confidence interval; NTD = New Taiwan dollar.

a. The data in this column are presented as n (%) or mean ± standard deviation.

Multivariate analysis identified the type of hypospadias as an independent risk factor for reoperation (Table 2). Distal hypospadias repair was significantly associated with a lower risk of reoperation than proximal repair [parameter estimate (PE), −1.38; odds ratio, 0.25; 95% confidence interval (CI), 0.07–0.88, p = 0.03]. Surgeons with high-volume caseloads had significantly lower likelihood of performing reoperation for hypospadias than low-volume surgeons despite statistical insignificance (PE, −2.62; odds ratio, 0.04; 95% CI, 0.01–0.86, p = 0.05).

Table 2. Multivariate analysis of risk factors significantly associated with hypospadias reoperation.

Variable	Parameter estimate	Standard error	Wald chi-square	Odds ratio	95% CI	p
Type of hypospadias (distal vs. proximal)	−1.38	0.64	4.67	0.25	0.07–0.88	0.03
Surgeon caseload volume (high vs. low)	−2.62	1.26	4.31	0.04	0.01–0.86	0.05

CI = confidence interval.

4. Discussion

Hypospadias is a common surgery. However, previous results of hypospadias surgery have mainly come from single institutions or single surgeons with extensive experience. In clinical practice, hypospadias surgeries are performed by surgeons with various kinds of specialty training (plastic surgery, pediatric surgery, or urology) and at various levels of hospitals. Few population-based studies on the general outcomes of hypospadias surgery have been conducted. Moreover, most previous studies have described only the complications immediately after hypospadias surgery. However, most complications after primary hypospadias repair, such as meatal stenosis, urethral fistulae, and breakdown of the neourethra, require additional surgical correction. The need for reoperation after hypospadias surgery could therefore be an indicator for surgical outcomes and medical care quality. In this population-based analysis, the total reoperation rates were estimated to be 15.7% and 8% for the distal type of hypospadias, comparable with previously published reports.⁹

The relationship between surgeon volume and outcomes in various surgeries has been widely discussed.¹⁰ Most previous studies have reported that outcomes and complications are inversely related to surgeon volume, especially for procedures that depend greatly on technique, such as cardiovascular and cancer surgery.^{11; 12 ;  13} In urology, the association between volume and outcomes has been widely studied in high-risk oncological surgeries, particularly in radical prostatectomy and cystectomy.^{14 ;  15} However, the relationship between volume and outcomes for hypospadias surgery has not been well established. According to previous hospital-based studies, the complications of hypospadias surgery and the need for additional procedures are associated with surgeon experience, patient age, and the proximal location of the meatus. In another population-based analysis, surgeon volume was also identified as a risk factor for secondary surgery for hypospadias.¹⁶ However, numerous patient and hospital factors were not included in the analysis. To the best of our knowledge, the present study is one of only a few studies to examine the simultaneous impact of the hospital and surgeon volume on the outcomes of hypospadias. Surgeon volume reflects practice volume and is closely associated with the experience of medical care for patients. In addition, a marked learning curve for fellowship-trained pediatric urologists performing hypospadias repair has been illustrated in previous studies. Complications significantly decline with increasing experience in practice.⁴ In high-volume hospitals, trainees are exposed to many procedures, which thus shorten the learning curve. In the present study, we also analyzed the impact of other surgeon characteristics on the outcomes of hypospadias surgery. These characteristics included the specialty of the surgeon, her gender, the number of her board certifications, the years since her board certification, her age, and her caseload volume. Only surgeon caseload volume was significantly associated with the likelihood of reoperation in multivariate analysis.

The American Academy of Pediatrics¹⁷ reported that the optimal age for hypospadias surgery is between 6 months and 12 months. Healing seems to happen rapidly, with less intense scarring in younger infants. In addition, younger children experience less self-doubt.^{18; 19 ;  20} Age is a common risk factor for secondary surgery. Korvald and Stubberud²¹ reported that 5-year-old boys have a significantly higher incidence of fistulae (26% vs. 7%) and other complications (50% vs. 18%) than 1-year-old boys. In addition, Perlmutter et al⁵ reported a significantly higher reoperation rate in infants older than 6 months than in younger ones. In the present study, we found no association between increased age and a greater risk of secondary surgery or complications. This may be the consequence of a general delay in pediatric hypospadias surgery in Taiwan.²² Among the 89 patients who underwent repair surgery, approximately 60.6% (54 patients) received the primary repair after the age of 18 months. Therefore, age was not a predictor for secondary surgery in this study. Only these 89 (40.8%) of the 218 study patients with hypospadias underwent surgery during the study period. The possible reasons for the high proportion of nonoperation (59.2%) for hypospadias are as follows: First, the hypospadias of these patients were clinically insignificant (distal and mild, with minimal deformity); thus, surgical intervention may not be absolutely necessary.²³ The second reason is the possibility of delayed surgeries. In our previous study on the age of patients undergoing hypospadias surgery in Taiwan, approximately 60.6% of the patients received repair only after the age of 18 months.²²

Proximal and perineal hypospadias are common risk factors for a higher complication rate and additional procedures.⁹ Contemporary studies have proposed that the incidence of complications after proximal hypospadias repair is 15–45%.^{24 ;  25} The reoperation rate is also high in patients with penoscrotal or proximal shaft defects following tubularized incised plate urethroplasty.⁶ Herbst et al²⁶ reported that more than a quarter of patients who had received hypospadias repair at pediatric hospitals required additional interventions after what was thought to be definitive repair. The reoperation rate in our study sample was 25.6% for proximal hypospadias and 8% for distal, and the type of hypospadias based on the location of the meatus was an independent predictor of the likelihood of reoperation.

The present study is based on records generated by the accessible and often-used NHIRD, which has several advantages. First, it is a nationwide, population-based database which includes all medical claims for over 99% of the population of Taiwan. The results can therefore represent the general population as a whole. Second, the database contains original claims records for the studied population, and it was not designed for academic study, thereby attenuating bias in patient selection. Most importantly, we entered into the analysis all of the patient, surgeon, and hospital factors in the NHIRD which were potentially associated with the surgical outcomes of hypospadias.

There are some limitations to this study. First, it was a retrospective analysis, and the number of cases was small because the disease is rare. Second, the NHIRD lacked some important clinical information, such as the severity of the chordee, penile length, the quality of the urethral plate, the definite type of hypospadias and surgical procedure, the actual complications, and patient satisfaction after primary repair. Third, the insurance claims data inevitably contained a number of diagnostic errors. Nevertheless, the actual medical charts were spot-confirmed by competent record review teams. Fourth, an 11-year follow up may not be long enough to cover all the reoperations of our patients—some may have occurred beyond the study period. Finally, although the NHIRD includes all medical claims for > 99% of the entire population of Taiwan, the study may have missed those individuals whose medical services were not covered by the NHI.

The type of hypospadias surgery and surgeon volume were predictors associated with the need for reoperation. Proximal hypospadias independently increased the risk for reoperation for hypospadias. This nationwide study addresses an important clinical issue, and its findings provide important information on the outcomes of hypospadias repair for parents and specialists. Larger studies are needed to corroborate our results.

Acknowledgments

This study is based in part on data from the NHIRD provided by the NHI, Department of Health, Taiwan, and managed by the National Health Research Institutes, Taiwan.

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