This single-center prospective randomized parallel-group trial compares laser ablation and crystallized phenol application in adults with primary uncomplicated sacrococcygeal pilonidal sinus disease. The primary objective is to compare postoperative day 1 pain intensity between the two treatment methods. Secondary objectives include complete epithelialization by day 30, time to complete epithelialization, postoperative day 7 pain, duration of analgesic use, time to return to daily activities and work, early local complications, and 6-month recurrence.

This is a single-center, prospective, 1:1 parallel-group randomized clinical trial in adults with primary uncomplicated chronic sacrococcygeal pilonidal sinus disease. A total of 120 participants are planned, with 60 assigned to laser ablation and 60 assigned to crystallized phenol treatment. Randomization will be performed using computer-generated variable blocks, with stratification by pit number and Guner stage when feasible. Allocation concealment will be ensured using sequentially numbered, opaque, sealed envelopes. In both groups, a small incision of approximately 1 cm will be made, hair and debris within the sinus cavity will be removed, and curettage will be performed. After these shared preparation steps, the intervention group will receive Leonardo Mini 1470 nm diode laser treatment and the comparison group will receive crystallized phenol application. Repeat sessions with the same assigned treatment may be performed when needed within the secondary healing protocol. The primary endpoint is postoperative day 1 pain intensity measured by Visual Analog Scale. The main secondary endpoint is complete epithelialization at day 30. Other secondary outcomes include time to complete epithelialization, postoperative day 7 pain, duration of analgesic use, time to return to daily activities and work, early local complications, and recurrence at 6 months.

Inclusion Criteria:

• Age 18 years or older
• Diagnosis of primary chronic sacrococcygeal pilonidal sinus disease
• Uncomplicated disease
• Suitability for minimally invasive treatment
• Provision of written informed consent

Exclusion Criteria:

• Acute pilonidal abscess
• History of pilonidal abscess drainage
• Previous surgical or interventional treatment for pilonidal sinus disease
• Recurrent pilonidal disease
• Complex pilonidal disease or marked lateral extension
• Immunosuppression, chronic steroid use, or systemic conditions that may significantly impair wound healing
• Inability to attend regular follow-up
• Refusal to participate in the study

Individual participant data will not be shared because this is a single-center clinical study involving sensitive patient-level data, and there is no pre-specified institutional mechanism for external data sharing. Only aggregated, de-identified study results will be reported.