Pilonidal sinus disease is an acquired disorder of the natal cleft and its incidence is reported as 6 in 100,000. Although there are many opinions regarding the treatment of pilonidal sinus disease in the literature, surgery is the main treatment method. Regardless of the treatment protocol, this disease has a certain risk of recurrence. Therefore, the ideal treatment procedure for the pilonidal disease should be simple to perform, should allow patients to return earlier to work, should be associated with minimal pain, and should minimize financial cost.

Phenol application into the pilonidal sinus is an additional nonoperative adjunct to treatment. This method is typically used after all hair and debris have been removed or curetted from the sinus, and it helps to eliminate granulation tissue and further debris formation. The injection is followed by hair control and strict hygiene. The use of phenol causes an intense inflammatory reaction which destroys the epithelial lining, and care should be taken to protect the surrounding skin. Pain is intense and may require inpatient admission for pain control but success rates have been reported to range from 60% to 95%. However, it is difficult to know which patients can expect enough benefit from phenol application.

The aim of the study is to evaluate the factors affecting the outcomes of patients with the pilonidal disease treated with crystallized phenol and to evaluate long-term recurrence rates of pilonidal disease treated with crystallized phenol.

Pilonidal sinus disease is an acquired disorder of the natal cleft and its incidence is reported as 6 in 100,000. Although there are many opinions regarding the treatment of pilonidal sinus disease in the literature, surgery is the main treatment method. Regardless of the treatment protocol, this disease has a certain risk of recurrence. Therefore, the ideal treatment procedure for the pilonidal disease should be simple to perform, should allow patients to return earlier to work, should be associated with minimal pain, and should minimize financial cost.

Phenol application into the pilonidal sinus is an additional nonoperative adjunct to treatment. This method is typically used after all hair and debris have been removed or curetted from the sinus, and it helps to eliminate granulation tissue and further debris formation. The injection is followed by hair control and strict hygiene. The use of phenol causes an intense inflammatory reaction which destroys the epithelial lining, and care should be taken to protect the surrounding skin. Pain is intense and may require inpatient admission for pain control but success rates have been reported to range from 60% to 95%. However, it is difficult to know which patients can expect enough benefit from phenol application.

In this study, the procedure will be performed on an outpatient basis and the treatment procedure will be performed in the prone position. Previously shaved sacrococcygeal area will be cleaned with an antiseptic solution and local anesthesia will be achieved using 2% lidocaine (1:100,000 adrenaline). After sinuses are dilated with a mosquito clamp; hair, debris, and granulation tissue will be removed from the sinus tracts using a curved surgical forceps and the tracts will be curetted using a straight curette. Following the protection of the skin surrounding the sinus openings with a pomade and the perianal area with a sponge, the sinus cavity will be sclerosed using crystallized phenol. Crystallized phenol will be inserted into the sinus tract from the dilated sinus opening with a clamp until the tract is full. This procedure will repeat twice and each phenol particles will remain in sinus about one minute, and then will be removed by applying pressure. Consequently, the procedure will be completed after dressing and the patient will be sent home by prescribing an analgesic pill (paracetamol 500 mg) to use only when required.

After the patients are divided into two groups: (1) those successfully treated and (2) those with treatment failure, descriptive statistics will be presented as the means +/- standard deviations (SDs), medians and interquartile ranges (IQRs), and frequencies (%). Examinations of normal distribution assumptions for continuous variables will be visually assessed with quartile-quartile plots and histograms and confirmed with the Shapiro-Wilk test. Associations between variables will be evaluated using the Mann-Whitney U and Student's t tests (for continuous variables) or Pearson's chi-square and Fisher exact tests (for categorical variables), where appropriate.

The association of treatment success with demographics, symptom duration, and pilonidal sinus features such as the number and location of the sinuses, the amount of hair inside the sinus, the volume of the sinus tract, and the length of sinus tract will be analyzed with logistic regression analysis. First, each covariate will be analyzed in a univariate model, and all variables with p-value less than 0.20 will be included in the final multivariate logistic regression model to determine independent factors. Odds ratios (ORs) of statistically significant predictors will be presented with 95% confidence intervals (CIs). P values lower than 0.05 will be considered statistically significant.

Inclusion Criteria:

• Patients with symptoms due to chronic primary or recurring pilonidal sinus disease interfering with daily life
• Patients giving written informed consent
• Patients who can be contacted by e-mail or telephone
• Patients aged 18 years and older

Exclusion Criteria:

• Patients with no or minimal symptoms related to pilonidal sinus disease
• Patients with an acute pilonidal abscess or complex, multiple recurrent pilonidal diseases
• Patients who could not be contacted during the follow-up period.