High Rate of Major Morbidity after Surgical Excision for Pilonidal Disease

Abstract

Background:

Recurrent pilonidal disease has been reported to occur in up to 30% of patients after their initial infection. Surgical resection is often performed to prevent recurrence of disease, however, morbidity after surgical excision from incision complications and disease recurrence is common. The aim of this study was to quantify major morbidity after initial pilonidal excision.

Patients and Methods:

Patients with pilonidal disease who had initial excision procedures between 2011–2013 at hospitals reporting data to the Pediatric Health Information System (PHIS) were included. Predictors of the composite outcome of major surgical site complication or surgical re-excision within one year were evaluated using multivariable logistic regression models. Kaplan-Meier analysis was used to examine time to surgical re-excision.

Results:

Of the 1,932 patients included, 4.7% (n = 138) had a major surgical site complication, 8.0% (n = 154) had a surgical re-excision, and 8.7% experienced either event within one year of their initial excision. The majority of re-excisions for recurrent disease occurred during the first two years after the initial excision. Risk factors associated independently with a greater risk of the composite outcome included older age (odds ratio [OR] 1.04 [95% confidence interval {CI} 1.00–1.07), p = 0.03), male gender (OR 1.49 [95% CI 1.09–2.08), p = 0.01), and the presence of a complex chronic gastrointestinal condition (OR 4.33 [95% CI 1.96–9.59], p < 0.001).

Conclusions:

Surgical excision of pilonidal disease is often complicated by site complications and nearly 1 of 10 patients develop recurrent disease requiring re-excision within two years after their initial excision. Future research into alternative therapies to treat pilonidal disease is warranted.

Pilonidal disease is a painful and challenging disorder of the natal cleft. It is characterized by the development of epithelialized tracks and sinuses within the buttocks. Entrapped hair follicles become infected and chronic, painful wounds can develop [1]. It is a common condition, reportedly affecting 26 in 100,000 people in the general population and more than 1% of the adolescent and young adult male population [2,3]. Recurrent pilonidal disease is common, and recurrence rates after either initial incision and drainage (I&D) or resection have been reported to be as high as 30%–40% [1,4,5]. In addition, surgical site complications after resection with primary closure have been reported to be as high as 30% [4]. This morbidity associated with poor-healing incisions after surgical excision represents a substantial burden on patients [3,6 –9].

Some of the previous reports of high rates of pilonidal disease recurrence and surgical morbidity include minor complications, such as infections requiring antibiotic agents or small wound openings that can be managed in the outpatient clinic [4]. The aim of this study was to quantify major surgical morbidity, namely rates of major incision complications and recurrent excisions, after initial pilonidal excision at tertiary children's hospitals across the United States.

Patients and Methods

This study used data from the Pediatric Health Information System (PHIS), an administrative database managed by the Children's Hospital Association. The PHIS contains patient demographic information, International Classification of Diseases, 9th Revision–Clinical Modification (ICD-9-CM) diagnosis codes, and date-stamped procedure codes from 48 tertiary children's hospitals. Patients with pilonidal disease (any ICD-9-CM diagnosis code of 685.0 or 685.1) who had initial excision procedures (ICD-9 86.21) between 2011 and 2013 at 1 of the 29 hospitals that continuously submitted inpatient, observation, and ambulatory surgery encounters to PHIS during the study period were identified. The ICD-9 procedure code for excision of pilonidal cyst sinus encompasses all of types of excision procedures with the exception of I&D. Patients were followed through 2014 to detect return visits to the emergency department and re-admissions for complications or recurrence, as evidenced by a surgical re-excision. We attempted to capture patients' initial excision procedures by excluding patients with evidence of a previous excision procedure in the preceding two years.

Exposures and outcomes

Patient characteristics at the time of the initial surgical excision that were evaluated as predictors of surgical morbidity included demographic and socioeconomic characteristics (age, gender, race, ethnicity, primary payer, zip-code level household income) and clinical characteristics (presence or absence of abscess (ICD-9-CM 685.0 vs. 685.1), presence of complex chronic conditions, and whether an I&D had been performed in the previous year at an emergency department, observation, inpatient, or ambulatory surgery visit) [10]. The primary outcome of interest was major surgical morbidity that included emergency department visits or re-admissions for complication or undergoing a recurrent surgical excision procedure within one year. Time to re-excision was also evaluated, with recurrent procedures tracked through the end of 2014. Complications were defined using the following ICD 9 CM codes at return to emergency department, inpatient, or observation encounters: 566 abscesses of anal and rectal regions; 998.5 post-operative infections; 998.51 infected post-operative seroma; 998.59 other post-operative infections; 998.3, 998.3x wound dehiscence; and 998.83 non-healing surgical wound.

Statistical analysis

Patient characteristics at the time of initial surgical excision were reported using medians and interquartile ranges for continuous variables and frequencies and percentages for categorical variables. Comparisons between patients with and without the composite outcome of major surgical morbidity including wound complication or surgical re-excision within one year were made using Mann-Whitney U tests for continuous variables and Pearson χ² or Fisher exact tests for categorical variables. Independent predictors of the composite outcome were evaluated using multivariable logistic regression models fit using generalized estimating equations to account for the clustering of patients within hospitals. All patient characteristics evaluated were included in the initial multivariable model, with the exception of characteristics present in fewer than 20 patients. Variable selection was performed using backward elimination until all variables in the model were significant at p < 0.05. SAS version 9.3 (SAS Institute Inc., Cary, NC) was used for all statistical analyses.

Results

Across the 29 included hospitals, a total of 1,932 patients underwent a pilonidal excision procedure without a previous surgical excision procedure in the preceding two years (Fig. 1). Of the 1,932 patients included, 4.7% (n = 138) had a major surgical site complication, 8.0% (n = 154) had a surgical re-excision, and 8.7% experienced either event within one year of their initial excision. The evaluated demographic and clinical characteristics of these patients at the time of their first surgical excision and differences in these characteristics between patients who did and did not experience a surgical site complication or re-excision within one year are shown in Table 1.

FIG. 1.

Development of a cohort of patients undergoing a first pilonidal excision procedure.

Table 1.

Characteristics of Patients with an Initial Pilonidal Cyst Excision Procedure in 2011–2013

Parameter	Overall (n = 1,932)	No surgical site complication or re-excision within 1 year (n = 1,703)	Surgical site complication or re-excision within 1 year (n = 229)	p
Age in years	16 (14, 17)	16 (14, 17)	15 (14, 17)	0.82
Gender				0.004
Female	907 (46.9)	820 (48.2)	87 (38.0)
Male	1,025 (53.1)	883 (51.8)	142 (62.0)
Race (n = 1,800)				0.02
Asian or Pacific Islander	25 (1.4)	18 (1.1)	7 (3.1)
Black	224 (12.4)	205 (12.0)	19 (8.3)
White	1,318 (73.2)	1,155 (67.8)	163 (71.2)
Other	233 (12.9)	209 (12.3)	24 (10.5)
Ethnicity (n = 1,715)				0.048
Hispanic or Latino	310 (16.0)	283 (16.6)	27 (11.8)
Not Hispanic or Latino	1,405 (72.7)	1,226 (72.0)	179 (78.2)
Pilonidal abscess				0.29
No	1,504 (77.8)	1,332 (78.2)	172 (75.1)
Yes	428 (22.2)	371 (21.8)	57 (24.9)
Primary payer				0.67
Government	823 (42.6)	723 (42.5)	100 (43.7)
Private	1,018 (52.7)	902 (53.0)	116 (50.7)
Other	91 (4.7)	78 (4.6)	13 (5.7)
Median household income in patient's zip code (USD)^a	45,876 (35,688, 59,144)	45,846 (35,688, 59,525)	459,07 (34,769, 57,271)	0.54
Length of stay (days)	1 (1, 1)	1 (1, 1)	1 (1, 1)	0.80
Any chronic condition	208 (10.8)	181 (10.6)	27 (11.8)	0.59
Neurologic or neuromuscular	109 (5.6)	97 (5.7)	12 (5.2)	0.78
Cardiovascular	16 (0.8)	15 (0.9)	1 (0.4)	0.71
Respiratory	0 (0.0)	0 (0.0)	0 (0.0)	—
Renal and urologic	18 (0.9)	15 (0.9)	3 (1.3)	0.46
Gastrointestinal	24 (1.2)	16 (0.9)	8 (3.5)	0.005
Hematologic or immunologic	12 (0.6)	10 (0.6)	2 (0.9)	0.64
Metabolic	25 (1.3)	21 (1.2)	4 (1.7)	0.53
Other congenital or genetic defect	52 (2.7)	44 (2.6)	8 (3.5)	0.42
Malignancy	5 (0.3)	5 (0.3)	0 (0.0)	1.00
Premature and neonatal	2 (0.1)	1 (0.1)	1 (0.4)	0.22
Technology dependence	22 (1.1)	16 (0.9)	6 (2.6)	0.04
Transplantation	10 (0.5)	9 (0.5)	1 (0.4)	1.00
Previous incision and drainage procedure at the PHIS hospital in the year preceding excision				0.79
No	1,731 (89.6)	1,527 (89.7)	204 (89.1)
Yes	201 (10.4)	176 (10.3)	25 (10.9)

Data are expressed as n (%) or median (IQR).

Based on 2010 U.S. Census data.

As an emergency department, observation, inpatient, or ambulatory surgery patient. P values are from χ² or Fisher exact tests for categorical variables and Mann-Whitney U tests for continuous variables.

IQR = interquartile range; PHIS = Pediatric Health Information System.

Patients with a surgical site complication within one year after excision were more likely to undergo a surgical re-excision than patients without a surgical site complication (17% vs. 7.5%, p < 0.001). When time to re-excision was evaluated using Kaplan-Meier analysis, we found that the majority of re-excisions for recurrent disease occurred during the first two years after the initial excision (Fig. 2).

FIG. 2.

Kaplan-Meier curve for first time to first recurrent excision after initial excision.

In a multivariable regression model, the only patient characteristics associated independently with an increased risk for the composite outcome of major surgical morbidity were older age (odds ratio [OR] 1.04 [95% confidence interval {CI} 1.00–1.07], p = 0.03), male gender (OR 1.49 [95% CI 1.09–2.08], p = 0.01), and the presence of a gastrointestinal complex chronic condition (OR 4.33 [95% CI 1.96–9.59], p < 0.001; Table 2). Table 3 illustrates the number of patients with each gastrointestinal complex chronic condition diagnosis and the proportion of patients with the composite outcome by diagnosis.

Table 2.

Multivariable Model for Major Surgical Site Complication or Recurrent Excision within One Year of Initial Pilonidal Cyst Excision

Variable	Odds ratio (95% CI)	p
Age in years	1.04 (1.00–1.07)	0.03
Male	1.49 (1.09–2.08)	0.01
Gastrointestinal complex chronic condition	4.33 (1.96–9.59)	< 0.001

CI = confidence interval.

Table 3.

Gastrointestinal Complex Chronic Conditions in Patients with Pilonidal Disease [11]

Diagnosis code and title	Number of patients with this code at the time of the pilonidal cyst excision	Number of patients with this code at the time of the pilonidal cyst excision who had either a surgical site complication or a re-excision
5559–Regional enteritis of unspecified site	6	3
7515–Other congenital anomalies of intestine	6	0
V441–Gastrostomy status	5	2
5569–Ulcerative colitis, unspecified	3	1
7512–Atresia and stenosis of large intestine, rectum, and anal canal, congenital	3	0
V443–Colostomy status	3	0
7503–Tracheoesophageal fistula, esophageal atresia and stenosis, congenital	1	0
7513–Hirschsprung's disease and other congenital functional disorders of colon	1	0
V442–Ileostomy status	1	1
V444–Status of other artificial opening of gastrointestinal tract	1	1
V4572–Acquired absence of intestine (large) (small)	1	1
V553–Attention to colostomy	1	0

Discussion

Patients with pilonidal disease experience major morbidity after surgical excision. Almost 1 of 10 patients will have either a major surgical site complication or recurrent disease requiring a re-excision within one year of their initial excision. In this study, we found that older age, male gender, and the presence of a complex chronic gastrointestinal condition was associated with having either a surgical site complication or undergoing surgical re-excision within one year.

Previous studies have also reported older age and male gender to be associated with pilonidal disease recurrence. For example, Milone et al. [11] performed a prospective study of children and young adults that found that male gender, older age, obesity, smoking habit, recurrent disease, the presence of multiple orifices, and a greater distance between the most lateral orifice and midline predicted an increased risk of post-operative complications (infection and recurrence). In general, we would expect three times more males than females to have pilonidal disease. However, all of the PHIS institutions are tertiary referral centers, so that may explain why the overall general makeup of this cohort is different than the general population with almost equal proportions of males and females. Our finding that the presence of a gastrointestinal complex chronic condition is predictive of surgical morbidity has not been reported previously. The complex chronic gastrointestinal condition predictor is categorized into three subcategories: congenital anomalies, chronic liver conditions/cirrhosis, and inflammatory bowel disease [10]. One could surmise that other chronic anorectal conditions could further contribute to the inflammatory nature of pilonidal disease, most notably inflammatory bowel disease (IBD), which can affect the anus and rectum [12]. As noted in Table 3, a number of patients presenting with regional enteritis, gastrostomy, and congenital anomalies of the intestine had either a surgical site complication or underwent a recurrent pilonidal excision. This may in part be because of the treatment of these chronic gastrointestinal conditions. As an example, surgical site healing after surgical excision of pilonidal disease could be affected in the setting of medical treatment of IBD that often involves immunosuppressive therapies.

The high rate of major morbidity after initial excision of pilonidal disease is concerning. The PHIS represents data from large tertiary children's hospitals that treat many patients with pilonidal disease. These institutions and their surgeons likely have extensive experience caring for patients with pilonidal disease, yet almost 1 of 10 patients experienced major morbidity after surgical excision. In addition, the 9% rate of major wound complication or re-excision within one year detected in this study is likely an underestimate as patients who have a complication may seek treatment at other institutions that would not found in this database.

In our study, the PHIS administrative database offers an effective resource in which to evaluate the incidence of and risk factors for recurrence of pilonidal disease in patients treated in pediatric hospitals. However, this study had a number of limitations, including those present in all studies utilizing large administrative databases, such as data misclassification because of miscoding of diagnoses and procedures and missing data because of the provision of treatments at other institutions (for example, I&D procedures performed in an office setting). In addition, we could examine only outcomes that could be defined using ICD-9 diagnosis and procedure codes. For example, we attempted to capture surgical site complications as seen in vacuum-assisted closure (VAC) device applications and changes. However, we could identify few patients with charges for VAC therapy. Furthermore, the only ICD-9 procedure code for excision of pilonidal cyst sinus encompasses all of these types of excision; therefore, we could not differentiate recurrence rates based on the type of initial excision. Other potentially important parameters are also not either not available or not reliably recorded in the dataset including smoking habit, obesity, and outpatient/home medications. In addition, the reason for re-excision procedures is not included in this dataset. Last, we attempted to capture patients' first surgical excision procedure by excluding those patients with a previous surgical excision procedure at the same hospital within the preceding two years. However, it is possible that some patients would have had a surgical procedure at a different institution or more than two years earlier at the same institution.

Conclusion

Surgical excision of pilonidal disease in adolescents and young adults is often complicated by major morbidity. Surgical site complications or recurrent disease requiring re-excision are common during the first two years after their initial excision. The high rate of major morbidity after surgery warrants future research into alternative therapies to treat and prevent recurrence of pilonidal disease.

Footnotes

Acknowledgments

Author contributions are as follows. Study conception and design: J. Lopez, J. Cooper, K. Deans, P. Minneci; Data acquisition: J. Lopez, J. Cooper; Analysis and data interpretation: J. Cooper; Drafting of the manuscript: J. Lopez, J. Cooper; Critical revision: K. Deans, J. Cooper, P. Minneci.

This project was supported by intramural funding from the Research Institute at Nationwide Children's Hospital.

Author Disclosure Statement

All authors declare that they have no competing financial interests relevant to the data contained in this article.

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