ABSTRACT
Pilonidal sinus is a chronic inflammatory condition of the natal cleft that commonly affects young adults. Conventional surgical treatments, such as wide excision and flap reconstruction, are associated with large wounds and prolonged recovery. Phenol treatment has been reported as a minimally invasive alternative in several countries; however, clinical experience in Japan remains limited. We retrospectively reviewed patients with pilonidal sinus who underwent phenol treatment at our institution between 2020 and 2025. After excision of the midline pits and curettage of the sinus tract, undiluted phenol was injected into the cavity and subsequently neutralized with ethanol. Clinical data, including patient characteristics, number of pits, operative time, postoperative hospital stay, complications, and recurrence, were analyzed. A total of 11 patients were included in the study. The median age was 27 years (range, 13–50), and 10 patients were male. The median number of pits was 3 (range, 1–5). The median operative time was 32 min (range, 19–56), and the median postoperative hospital stay was 2 days (range, 1–6). Postoperative bleeding occurred in two patients and was successfully managed conservatively. No recurrence was observed during the follow‐up period (median, 331 days; range, 100–979). Phenol treatment for pilonidal sinus appears to be a simple and minimally invasive procedure associated with short hospitalization and favorable short‐term outcomes. This technique may represent a useful treatment option for pilonidal sinus in Japan.
Keywords: case series, minimally invasive treatment, phenol, pilonidal sinus
1. Introduction
Pilonidal sinus is a chronic inflammatory condition that typically occurs in the natal cleft of young adults (Figure 1A) [1]. The disease is thought to result from the penetration of hair into the skin, leading to the formation of sinus tracts and recurrent inflammation (Figure 1B,C). Although various surgical techniques have been proposed, including wide excision with or without flap reconstruction, the optimal treatment remains controversial because of postoperative morbidity and delayed wound healing [2, 3]. Conventional surgical approaches, such as wide excision, are commonly performed (Figure 1D), whereas minimally invasive approaches targeting the sinus cavity, including phenol treatment, have recently been introduced (Figure 1E). In recent years, minimally invasive approaches have been introduced to reduce surgical trauma and shorten recovery time. Among them, phenol treatment has been reported as a simple and effective option in several studies, particularly in Europe and the Middle East [4, 5, 6, 7, 8]. However, clinical experience with this technique has rarely been reported in Japan, where conventional excision procedures remain commonly performed. In this study, we evaluated the clinical outcomes of phenol treatment for pilonidal sinus in a series of patients treated at our institution.
FIGURE 1.
Clinical features of pilonidal sinus and schematic illustration of the lesion. (A) Clinical photograph showing a typical pilonidal sinus in the sacrococcygeal region with visible pits along the midline. (B, C) Schematic illustration showing hair penetration (B) and sinus tract formation beneath the skin (C). (D, E) Illustration of the concept of minimally invasive treatment targeting the sinus cavity. (D) Conventional surgery (wide excision), (E) Phenol treatment.
2. Methods
2.1. Study Design and Patients
This retrospective study included patients with pilonidal sinus who underwent phenol treatment at our institution between 2020 and 2025. The diagnosis of pilonidal sinus was based on clinical findings, including the presence of midline pits or sinus openings in the natal cleft. Since 2020, phenol treatment has been adopted as the first‐line treatment for pilonidal sinus at our institution. Clinical data were obtained from medical records and preoperative clinical photographs when available. The study was approved by the Institutional Review Board for Research in Life Sciences and Medicine involving Human Subjects of the University of the Ryukyus (approval number: 25‐2535‐00‐00‐00), and an opt‐out consent procedure was used. No written consent has been obtained from the patients as there is no patient‐identifiable data included.
2.2. Surgical Procedure
Our protocol was based on the liquid phenol technique reported by Schneider et al., who used 80% liquid phenol retained for approximately 1 min followed by aspiration and saline irrigation [7]. We modified this protocol by using commercially available phenol solution for ingrown toenail surgery (approximately 90%), which is routinely used in dermatologic practice in Japan, and by adding ethanol irrigation based on our dermatologic experience with phenolization procedures.
The procedure was performed with the patient in the prone position. The midline pit and surrounding skin were excised with approximately a 5‐mm margin using a No. 15 scalpel (Figure 2A). A probe was inserted into the sinus tract to identify its extent, and hair and granulation tissue within the tract were removed by curettage using a sharp curette (Figure 2B). To protect the surrounding skin from chemical injury, a barrier was created around the wound using gentamicin ointment or white petrolatum. Undiluted phenol was then injected into the sinus tract using a syringe until the cavity was completely filled (Figure 2C). Commercially available phenol solution (approximately 90%) used for ingrown nail surgery was utilized. In most cases, approximately 3–5 mL of phenol was sufficient to fill the tract. The phenol was retained within the tract for approximately 90 s and subsequently aspirated. The cavity was then irrigated with absolute ethanol, followed by irrigation with normal saline (Figure 2D). Ethanol irrigation was performed to reduce residual phenol within the cavity and minimize chemical injury to the surrounding tissue. After removal of necrotic tissue and confirmation of hemostasis, a hemostatic dressing (Kaltostat, ConvaTec) was placed in the cavity. The wound was covered with topical gentamicin and dressed with gauze. The procedure was performed as a single‐session treatment, and repeated phenol applications were not routinely scheduled. The detailed surgical procedure is demonstrated in Video S1. Postoperative hair management, including shaving and recommendation of laser epilation, was advised during follow‐up.
FIGURE 2.
Procedure of minimally invasive phenol treatment for pilonidal sinus. (A) Excision of the pit using a scalpel (blue arrows). (B) Curettage of the sinus cavity to remove hair and granulation tissue. (C) Injection of phenol into the cavity to achieve chemical ablation. (D) Irrigation with ethanol followed by saline to reduce and wash out residual phenol (see also Video S1).
2.3. Outcome Measures
Clinical data collected included patient demographics, number of midline pits, anesthesia type, operative time, healing time, length of postoperative hospital stay, and complications. Recurrence was defined as the reappearance of a sinus opening, discharge, or inflammation in the natal cleft after initial healing.
3. Results
All patients had primary pilonidal sinus, and none had undergone previous surgery. A total of 11 patients with pilonidal sinus underwent phenol treatment during the study period (Table 1). The median age of the patients was 27 years (range, 13–50), and 10 patients were male. The number of midline pits was 1 in two patients, 2 in three patients, and ≥ 3 in six patients. The procedure was performed under local anesthesia in five patients, general anesthesia in two patients, and spinal anesthesia in four patients. The median operative time was 32 min (range, 19–56). The median postoperative hospital stay was 2 days (range, 1–6). Postoperative bleeding occurred in 2 of 11 patients. In both cases, the bleeding was successfully controlled by local packing with hemostatic material, and no additional surgical intervention was required. Complete epithelialization was achieved in 11 patients. The median healing time was 37 days (range, 8–267 days). No recurrence was observed during the follow‐up period (median, 331 days; range, 100–979).
TABLE 1.
Clinical characteristics and outcomes of patients treated with phenol for pilonidal sinus.
| Case | Age | Sex | Anesthesia | Pit number | Operation time (minute) | Postoperative hospital stay (day) | Healing time (day) | Follow‐up (day) | Complications | Recurrence |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 32 | Male | Local | 4 | 50 | 2 | 16 | 979 | Postoperative bleeding | No |
| 2 | 31 | Male | Spinal | 2 | 32 | 2 | 9 | 804 | None | No |
| 3 | 50 | Male | Spinal | 2 | 25 | 3 | 37 | 128 | None | No |
| 4 | 42 | Male | Local | 3 | 38 | 3 | 22 | 225 | Postoperative bleeding | No |
| 5 | 13 | Female | General | 5 | 35 | 6 | 267 | 590 | None | No |
| 6 | 17 | Male | Local | 4 | 30 | 3 | 58 | 191 | None | No |
| 7 | 16 | Male | Spinal | 2 | 51 | 2 | 37 | 531 | None | No |
| 8 | 27 | Male | Spinal | 3 | 32 | 2 | 8 | 100 | None | No |
| 9 | 25 | Male | Local | 1 | 22 | 2 | 37 | 393 | None | No |
| 10 | 26 | Male | Local | 1 | 19 | 1 | 30 | 331 | None | No |
| 11 | 40 | Male | General | 4 | 56 | 3 | 122 | 300 | None | No |
| Median 27 years (range, 13–50) |
Male: 10 Female: 1 |
Median 3 (range, 1–5) | Median 32 min (range, 19–56) | Median 2 days (range, 1–6) | Median 37 days (range, 8–267) | Median 331 days (range, 100–979) |
Note: Healing time was calculated in patients who achieved complete epithelialization. Patient demographics, operative details, and postoperative outcomes of the treated cases are summarized.
4. Discussion
In this study, phenol treatment for pilonidal sinus showed favorable clinical outcomes, including minimal surgical invasiveness and short hospitalization. Most patients were discharged within a few days after surgery, and no recurrence was observed during the follow‐up period. Healing time varied substantially among patients. In particular, one patient (Case 5) with multiple pits required a relatively large excision area, resulting in prolonged epithelialization over 267 days. Postoperative bleeding occurred in two patients but was successfully controlled with local packing. These findings suggest that phenol treatment may represent a useful minimally invasive option for selected patients with pilonidal sinus.
Pilonidal sinus has traditionally been treated by wide surgical excision with or without flap reconstruction [2, 3, 9]. Although these procedures aim to remove the sinus tract completely, they often result in relatively large wounds and prolonged recovery periods. Various minimally invasive approaches have therefore been proposed to reduce surgical morbidity and facilitate early return to daily activities. Among these techniques, phenol treatment has been widely reported as a simple procedure with acceptable recurrence rates [4, 5, 6, 7, 8]. Despite these reports, phenol treatment has rarely been described in the Japanese literature. In Japan, conventional excision procedures remain the standard surgical approach, and minimally invasive techniques have not been widely adopted. Several factors may contribute to this situation, including long‐standing surgical preferences for excisional procedures and limited familiarity with chemical ablation techniques among clinicians. The lack of domestic clinical reports may also have hindered the dissemination of this technique. In our procedure, absolute ethanol irrigation was performed after phenol application and before saline irrigation. This step was adopted based on the established phenolization technique used in the treatment of ingrown toenails in dermatologic practice in Japan and may help reduce chemical injury to the surrounding tissue [10].
The present study has several limitations, including the small number of patients and the relatively short follow‐up period. Larger studies with longer follow‐up are needed to further evaluate the long‐term efficacy of this technique. In addition, comparative studies with conventional surgical procedures, such as wide excision, are warranted to further clarify the relative efficacy of phenol treatment. In addition, postoperative hair management including shaving and laser epilation may also have contributed to the favorable recurrence outcomes observed in this study. Nevertheless, our findings indicate that phenol treatment could be a useful minimally invasive treatment option for pilonidal sinus in Japan.
Funding
The authors have nothing to report.
Ethics Statement
The study was approved by the Institutional Review Board for Research in Life Sciences and Medicine involving Human Subjects of the University of the Ryukyus (approval number: 25‐2535‐00‐00‐00). An opt‐out consent procedure was used. The study was conducted in accordance with the Declaration of Helsinki.
Conflicts of Interest
The authors declare no conflicts of interest.
Supporting information
Video S1: Surgical procedure of minimally invasive phenol treatment for pilonidal sinus. This video demonstrates the key steps of minimally invasive phenol treatment for pilonidal sinus, including pit excision, curettage of the sinus cavity, phenol injection, and subsequent ethanol irrigation to neutralize the phenol. The procedure is shown in a representative case.
Acknowledgments
The authors have nothing to report.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Video S1: Surgical procedure of minimally invasive phenol treatment for pilonidal sinus. This video demonstrates the key steps of minimally invasive phenol treatment for pilonidal sinus, including pit excision, curettage of the sinus cavity, phenol injection, and subsequent ethanol irrigation to neutralize the phenol. The procedure is shown in a representative case.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.