Early Outcomes of Laparoscopic Versus Open Surgery for Urachal Remnant Resection in Children: A Retrospective Analysis Using a Nationwide Inpatient Database in Japan

Abstract

Background:

There was no large study that assessed the surgical safety of laparoscopic surgery (LS) for urachal remnant resection. This study compared early postoperative outcomes between LS and open surgery (OS) for pediatric urachal remnant resection, using a national inpatient database.

Patients and Methods:

Using the Diagnosis Procedure Combination database in Japan, we compared postoperative complications, duration of anesthesia, postoperative length of stay, and total hospitalization cost between LS and OS for children undergoing urachal remnant surgery from April 2015 to March 2017. Propensity score-adjusted analyses were performed for outcomes.

Results:

Among 882 eligible patients (306 LS; 576 OS), there were no significant differences between LS and OS for postoperative complications (odds ratio: 1.02; 95% confidence interval [CI]: 0.48–2.18; P = .96) and postoperative length of stay (difference: 0.14 day; 95% CI: −0.27 to 0.54; P = .39). Compared with OS, LS had significantly longer duration of anesthesia (difference: 51 minutes; 95% CI: 42–60; P < .001) and significantly higher total hospitalization cost (difference: US$824; 95% CI: 399–1249; P < .001).

Conclusions:

In this large nationwide cohort study, LS for urachal remnant resection was associated with longer duration of anesthesia and higher total hospitalization cost. However, no differences were detected between LS and OS regarding postoperative complications and length of stay. LS for urachal remnant resection is equivalent to OS in terms of surgical safety.

Introduction

Urachal remnant is a rare congenital anomaly and presents as urachal cyst, urachal diverticulum, urachal sinus, patent urachus, or nonspecific atretic urachal remnant urachus fistula.¹ It occurs in ∼1/5000 births.² Urachal remnant may be repetitively infected and has the potential for malignant change; therefore, surgical resection is necessary. Open surgery (OS) is generally performed for urachal remnant resection, but sometimes requires a large midline infraumbilical or lower abdominal transverse incision. In various abdominal surgeries, the open approach is associated with longer convalescence, larger and worse scar, and increased postoperative bowel obstruction.^3–6 Therefore, laparoscopic surgery (LS) for urachal remnant resection is becoming widespread in both adults and children. Previous studies^2,7–11 recommended LS for urachal remnant resection because it was safe, ensured good cosmesis, and provided an excellent view of the surgical field (magnification). Almost all of these previous studies were case reports or case series. Only two previous studies compared the postoperative outcomes between LS and OS, but the evaluation was limited by the small sample size.^12,13 To date, no large studies have assessed the surgical safety of LS for pediatric urachal remnant resection. As the numbers of such operations are small in individual institutions, it is difficult to evaluate the outcomes between LS and OS in a single-center study. Therefore, this study was conducted to compare the postoperative outcomes following LS and OS for urachal remnant resection in children using a national inpatient database in Japan.

Materials and Methods

Data sources

For this retrospective cohort study, we used the Diagnosis Procedure Combination database, a nationwide inpatient database in Japan. The database includes hospital administrative claims information and discharge abstracts in the form of anonymized data from more than 1000 participating hospitals. The database includes the following data: unique hospital identifier; patient age, body weight, body height, and sex; diagnoses, comorbidities at admission, and complications after admission recorded with text data in the Japanese language and International Classification of Diseases, Tenth Revision (ICD-10) codes¹⁴; procedures; and length of stay. The details of the database have been described elsewhere.¹⁵ The database was validated in a previous study.¹⁵

This study was based on a secondary analysis of the administrative claims data. The requirement for informed consent was waived because of the anonymous nature of the data. Study approval was obtained from the Institutional Review Board at The University of Tokyo.

Patient selection

We extracted all children (age: 0–18 years) who underwent LS or OS for primary excision of urachal remnant from the database between April 2015 and March 2017. We excluded patients who underwent other operations, except for drainage of infected urachal remnant, umbilicoplasty, or dermatoplasty during the same hospitalization.

Outcomes

The primary outcome was postoperative complications. Secondary outcomes included duration of anesthesia, postoperative length of stay, and hospitalization cost. Postoperative complications consisted of one of the following items: reoperation, surgical-site infection (ICD-10 codes: T79.3, T81.4; Japanese text diagnosis), surgical-site bleeding (T810), peritoneal bleeding (K661), peritonitis/peritoneal abscess (K65), urinary tract infection (N10, N30, and N39.0), respiratory complications (J14–18, J95.8, J95.9, J96.0, and J96.9), shock (R57), ileus and intestinal obstruction (K56.0-2, K56.5-7, and K913), and injury to organ (S36.4, S36.5, and S37.2).

Other extracted variables were sex, age, body weight, body height, associated anomalies, elective or emergency admission, the number of infected urachal remnants requiring hospitalization before resection, history of incisional or percutaneous drainage for urachal remnant abscess before resection, teaching or nonteaching hospital, department of hospitalization (pediatric surgery or other department), and annual hospital volume for urachal remnant resection. Age was categorized into three groups: <6 years, 6–12 years, and 13–18 years. Weight was also categorized into three groups: <10 kg, 10–29.9 kg, and ≥30 kg. Body height was categorized into tertiles, resulting in almost equal numbers of patients in three groups: <98 cm, 98–156 cm, and ≥157 cm. Hospital volume was defined as the average annual number of urachal remnant resections performed at each hospital and was categorized into halves, resulting in almost equal numbers of patients in two groups. We identified the associated congenital anomalies and the circulatory system, which was recorded with the following ICD-10 codes: Q0–Q9 or Q20–28.

Statistical analyses

We performed unadjusted analyses for primary outcomes in all patients and subgroups divided according to patient age and body weight. In univariate comparisons, categorical variables were compared by the χ² test and Fisher's exact tests, and continuous variables were compared by the t-test or Mann–Whitney U test. An unadjusted comparison using observational data is affected by many confounding biases. To balance the measured potential confounders between the two groups, we used propensity score-adjusted analyses to compare the outcomes between the LS and OS groups. We estimated a propensity score for undergoing LS using generalized estimating equations. To adjust for clustering within hospitals, the generalized estimating equations were fitted with logistic regression models. The predictor variables included sex, age, any congenital anomaly, the number of infected urachal remnants requiring hospitalization before resection, history of incisional or percutaneous drainage for urachal remnant abscess before resection, elective or emergency admission, department of hospitalization, and annual hospital volume for urachal remnant resection. The C-statistic was calculated with the area under the receiver operating characteristic curve to evaluate the model predicting to undergo LS. We then performed logistic regression for postoperative complications and linear regression for secondary outcomes, in which treatment allocation (LS or OS) and propensity scores were used as dependent variables. All analyses were two tailed, and P values of <.05 were considered statistically significant. The analyses were conducted using Stata/MP 15.0 (Stata Corp., College Station, TX).

Results

We identified 946 patients who underwent surgery for urachal remnant resection in 177 hospitals during the study period. We excluded patients who underwent other operations during the same hospitalization (n = 54) and those who had missing data on outcomes, weight, and height (n = 10). Thus, 882 eligible patients (306 LS patients and 576 OS patients) were identified. About 35% of pediatric patients underwent LS for urachal remnant resection.

The baseline characteristics of the patients in the two groups are summarized in Table 1. There were no significant differences in patient characteristics, including sex, cardiac anomaly, and type of hospital, between the LS and OS groups. Patients with greater height, heavier weight, and older age tended to undergo LS. LS was likely to be undertaken by departments other than pediatric surgery (including general surgery).

Table 1.

Background Characteristics of the Patients in the Laparoscopic and Open Surgery Groups

	Laparoscopic surgery (N = 306)		Open surgery (N = 576)		Total (N = 882)		P value
	n	%	n	%	n	%	P value
Sex							.51
Male	194	63.4	378	65.6	572	64.9
Female	112	36.6	198	34.4	310	35.1
Age (years), median (IQR)	15.3 (11.4–17.2)		9.5 (1.7–14.4)		12.1 (5.0–16.0)		<.001
<6	21	6.9	221	38.4	242	27.4	<.001
6–12	81	26.5	156	27.1	237	26.9
13–18	204	66.7	199	34.5	403	45.7
Weight (kg), median (IQR)	49.2 (35.3–56.7)		28.9 (10.6–47.6)		37.1 (17.3–52.8)		<.001
<10	6	2.0	132	22.9	138	15.6	<.001
10–29.9	48	15.7	162	28.1	210	23.8
≥30	252	82.4	282	49.0	534	60.5
Height (cm), median (IQR)	159 (144–169)		131 (81–157)		147 (105–163)		<.001
<98	14	4.6	185	32.1	199	22.6	<.001
98–156	121	39.5	242	42.0	363	41.2
157	171	55.9	149	25.9	320	36.3
Any anomaly	5	1.6	36	6.3	41	4.6	.002
Cardiac anomaly	1	0.3	5	0.9	6	0.7	.35
Emergency admission	6	2.0	39	6.8	45	5.1	.002
Number of infected urachal remnants requiring hospitalization before resection							<.001
0	137	44.8	412	71.5	549	62.2
1	146	47.7	144	25.0	290	32.9
≥2	23	7.5	20	3.5	43	4.9
Abscess drainage for infected urachal remnant before resection	13	4.2	8	1.4	21	2.4	.008
Type of hospital							.54
Nonteaching	36	11.8	60	10.4	96	10.9
Teaching	270	88.2	516	89.6	786	89.1
Department of hospitalization							<.001
Pediatric surgery	88	28.8	307	53.3	395	44.8
Others	218	71.2	269	46.7	487	55.2
Annual hospital volume for resection of a urachal remnant							<.001
Low (<2)	188	61.4	242	42.0	430	48.8
High (≥2)	118	38.6	334	58.0	452	51.2

IQR, interquartile range.

In the unadjusted analyses for all patients (Table 2), there was no significant difference in the proportion of postoperative complications between the LS and OS groups (4.9% versus 4.2%; P = .61; Table 2). Similarly, there were no significant differences in the proportions of postoperative surgical site infections (2.6% versus 2.1%; P = .64), respiratory complications (0.7% versus 0.0%; P = .12), and urinary tract infections (1.0% versus 1.6%; P = .56) (LS versus OS groups, respectively). There were no postoperative intestinal obstructions requiring hospitalization in either the LS or OS group during the 1 year after discharge from a hospital. Table 2 also shows unadjusted analyses for duration of anesthesia, postoperative length of stay, and total hospitalization cost for the LS and OS groups. Duration of anesthesia was significantly longer in the LS group compared with the OS group (mean [standard deviation]: 191 [69] minutes versus 134 [53] minutes; P < .001). There were no significant differences in postoperative length of stay (mean [standard deviation]: 4.8 [2.1] days versus 4.5 (4.3) days; P = .16) and total hospitalization cost (mean [standard deviation]: US$4929 [1023] versus US$4725 [3437]; P = .31) between the LS and the OS groups.

Table 2.

Unadjusted Comparisons of Postoperative Complications, Duration of Anesthesia, Postoperative Length of Stay, and Total Hospitalization Cost Following Laparoscopic and Open Surgery in all Patients

	Laparoscopic surgery (N = 306)	Open surgery (N = 576)	Total (N = 882)	P value
Postoperative complications, n (%)	15 (4.9)	24 (4.2)	39 (4.4)	.61
Duration of anesthesia (minutes), mean (SD)	191 (69)	134 (53)	153 (65)	<.001
Postoperative length of stay (days), mean (SD)	4.8 (2.1)	4.5 (4.3)	4.6 (3.7)	.16
Total hospitalization cost (US$), mean (SD)	4929 (1023)	4725 (3437)	4796 (2843)	.31

SD, standard deviation.

In the unadjusted analyses for all subgroups divided according to patient age and weight (Table 3), we found no significant difference in the proportion of postoperative complications between the LS and OS groups.

Table 3.

Unadjusted Comparisons of Postoperative Complications Between Laparoscopic and Open Surgery Groups in Each Subgroup Divided According to Patient Age or Weight

	Laparoscopic surgery (n = 306)		Open surgery (n = 576)		Total (n = 882)		P value
	n	%	n	%	n	%	P value
Age (years)
<6 (n = 242)	0/21	0.0	14/221	6.3	14/242	5.8	.62
6–12 (n = 237)	2/81	2.5	6/156	3.9	8/237	3.4	.72
13–18 (n = 403)	11/204	5.4	4/199	2	15/403	3.7	.11
Weight (kg)
<10 (n = 138)	0/6	0.0	11/132	8.3	11/138	8	1.00
10–29.9 (n = 210)	0/48	0.0	5/162	3.1	5/210	2.4	.59
≥30 (n = 534)	13/252	5.2	8/282	2.8	21/534	3.9	.19

Table 4 shows the results of the propensity score-adjusted logistic regression. The C-statistic for the model calculating propensity scores was 0.75. There was no significant difference in the proportion of postoperative complications between the LS and OS groups (odds ratio, 1.02; 95% confidence interval [CI], 0.48–2.18; P = .96).

Table 4.

Propensity Score-Adjusted Logistic Regression Analysis for Postoperative Complications Between Laparoscopic and Open Surgery for Urachal Remnant Resection

	Postoperative complications		P value
	Odds ratio	(95% CI)	P value
Operation
Open surgery	Ref
Laparoscopic surgery	1.02	(0.48–2.18)	.96

CI, confidence interval; Ref, reference.

In the propensity score-adjusted liner regression (Table 5), there was no significant difference in postoperative length of stay between the LS and OS groups. However, significant differences in total hospitalization cost (difference: US$824; 95% CI: 399–1249; P < .001) and duration of anesthesia (difference: 51 minutes; 95% CI: 42–60; P < .001) were observed between the two groups.

Table 5.

Propensity Score-Adjusted Linear Regression for Duration of Anesthesia, Postoperative Length of Stay, and Total Hospitalization Cost Between Laparoscopic and Open Surgery for Urachal Remnant

	Difference	(95% CI)	P value
Duration of anesthesia (minutes)	50.6	(41.5–59.6)	<.001
Postoperative length of stay (days)	0.14	(−0.27–0.54)	.39
Total hospitalization cost (US$)	824	(399–1249)	<.001

CI, confidence interval.

Discussion

This study demonstrated substantial differences in patient characteristics between the LS and OS groups. Therefore, we performed propensity score-adjusted analyses to control for confounding biases on the basis of measured confounders. Our major findings were the lack of significant differences in proportion of postoperative complications and postoperative length of stay between the LS and OS groups. LS was associated with longer duration of anesthesia and higher total hospitalization cost compared with OS.

Although surgical resection can often be done with an umbilical incision only for infants and small children, it requires a large incision at a site other than the umbilicus for nonpetite children. The traditional approach to total excision of urachal lesions in children is a large midline infraumbilical or lower abdominal transverse incision. Accordingly, the laparoscopic approach has become popular for urachal remnant resection along with minimally invasive surgery in any operation.

Several previous studies showed that LS was safe for urachal remnant resection.^{7,8,11,16–19} However, these studies were only case reports or small case series in pediatric remnant resection. This study is the first to directly compare outcomes between LS and OS for urachal remnant resection in children using a large-scale database.

In previous pediatric case series of LS,^7,8,17–20 duration of surgery was 19–130 minutes. Unfortunately, the database we used in this study lacked data on skin-to-skin surgical time; however, we were able to obtain data on duration of anesthesia, which was longer than surgical duration because preparing the surgical instruments is included in the duration of anesthesia.

Several studies with small sample sizes (n = 16–108) reported proportions of postoperative complications of 0%–14.7% in pediatric urachal remnant resection.^1,19,21,22 These proportions were relatively high compared with that in this study (4.4%). This discrepancy may be due to differences in the study populations and sample sizes. Other small studies demonstrated that there were no significant differences in postoperative complications, length of hospital stay, and duration of surgery between the LS and OS groups.^12,13 However, these results were not generalizable because the study was based on limited experiences at a single center. Our multicenter large-scale study provides more reliable data and confirms results produced in previous studies.

In this study, substantial differences were seen in patient age and weight between the LS and OS groups, suggesting that selection of LS or OS may be largely dependent on body habitus. After adjusting for patient background characteristics, our study showed no significant difference in proportion of postoperative complications and length of stay between the LS and OS groups.

In this study, the total hospitalization cost in the LS group was higher than that in the OS group. Because length of stay did not differ significantly, the difference in total cost may be explained by the relatively high cost of the surgical equipment for LS. Cosmetic merits in LS are evident, but LS is relatively costly. Further studies are needed to evaluate the cost-effectiveness of LS compared with OS.

Several limitations should be considered when interpreting the results of this study. First, the database lacked information on operative findings and imaging findings, including the type of urachal remnant (urachal diverticulum or sinus), type of procedure (total or partial resection), and the size of the urachal remnant. However, the type of urachal remnant is definitively diagnosed after surgery, and the type of procedure is chosen during surgery. These factors do not affect the treatment allocation of LS or OS, and thus should not be included when estimating the propensity scores. These factors are prognostic factors rather than confounders, and they may have little, if any, impact on outcomes. Remnant size is a possible confounder; however, very large urachal remnants are rare, so bias related to this confounding factor may be small.

Second, we could not confirm conversion from LS to OS, although the conversion rate may be low.¹⁸ The database also lacked postdischarge data, and therefore, we could not confirm long-term outcomes (e.g., malignant alterations and recurrence).

Conclusions

In our large national database study, proportion of postoperative complications and length of stay did not differ significantly between LS and OS for urachal remnant resection in children. Total hospitalization cost was higher in the LS group than in the OS group. We showed that LS for urachal remnant resection was equivalent to OS regarding surgical safety, in our large patient group.

Footnotes

Acknowledgments

This work was supported by grants from the Ministry of Health, Labour and Welfare, Japan (H29-Policy-Designated-009 and H29-ICT-General-004), and the Ministry of Education, Culture, Sports, Science and Technology, Japan (17H04141).

Disclosure Statement

No competing financial interests exist.

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