Infected pilonidal sinuses are a common pathology, affecting an estimated 0.7% of the population. In France, the most commun technique is extended exeresis with an open wound, followed by directed healing. This technique reduces the risk of recurrence, albeit at the cost of daily nursing care and a long healing period involving prolonged absence from work. Closure or plasty surgical techniques aimed at reducing the duration of nursing care are more restrictive, and seem to have higher recurrence rate. Minimally invasive treatment, such as phenolization and flattening with curettage of the sinus have existed for over 50 years, albeit with disappointing long-term results and morbidity that limits their application.

Today, new minimally invasive treatments are being developed, aiming at a less constraining post-operative period. without compromising healing. These include glue, endoscopic treatment (EPSiT : Endoscopic Pilonidal Sinus Treatment or VAASP : Video-Assisted Ablation of Pilonidal Sinus) and laser treatment (SiLaT procedure : Sinus Laser Therapy or PiLaT : Pilonidal disease Laser Treatment).

Laser treatment is used since 2014 in the treatment of anal fistulas and more recently in the treatment of infected pilonidal sinus. A laser fiber is introduced, under local or general anaesthesia, into the main cavity and secondary tracts after curettage and opening of the dimples. The energy delivered by the laser is transmitted in the form of heat, in order to seal the cavity during healing of thermal lesions.

Initial results report success rates of around 90%, with a healing time of between 1 and 2 months. It also appears to be effective after failure of previous surgery. In cases of incomplete closure or recurrence, a second laser treatment can be performed with high healing rates. The investigators carried out an retrospective study including 29 patients treated with the SILAT technique. The healing rate, defined as the absence of symptoms and recurrence of suppuration, was around 70%. The procedure was painless and no serious complications were observed. The presence of one or more secondary orifices and overweight were associated with a higher risk of failure.

In order to confirm these results, to better specify the factors predictive of success, and to evaluate the efficacy of SiLaT in the longer term, the investigators will carry out a single-center study including all adult patients treated with laser between June 2018 and December 2020.

Inclusion Criteria:

• Patient aged 18 or above
• French-speaking patient
• Patient hospitalized in the Proctology department of GHPSJ between 01JUN2018 and 31DEC2020 for a chronically infected pilonidal sinus
• patient presenting an recurring infected pilonidal sinus after open or closed surgical treatment

Exclusion Criteria:

• Patient hospitalized in the acute abcess stage of an infected pilonidal sinus
• Patient under guardianship or curatorship
• Patient incarcerated
• Patient under legal protection
• Patient refusing enrollment

Patient hospitalized in the Proctology department of GHPSJ between 01JUN2018 and 31DEC2020 for a chronically infected pilonidal sinus