Scar Endometriosis: Etiology and Management
Etiology
Scar endometriosis develops through iatrogenic implantation of endometrial tissue into surgical wounds during pelvic procedures, most commonly cesarean section (occurring in 68.8% of cases). 1
The pathophysiologic mechanism involves:
- Direct contamination of the surgical wound with endometrial cells during uterine incision, particularly at cesarean delivery, hysterotomy, or laparoscopic port sites 2, 1
- Endometrial tissue becomes embedded in the subcutaneous tissue and rectus sheath, where it responds to cyclic hormonal stimulation 1
- The condition develops in 1-2% of patients following cesarean section 3
Key risk factor: Prior cesarean section is the inciting surgery in approximately 70% of cases, followed by laparoscopic procedures for endometriosis (18.7% presenting as port site endometriosis) 1
Clinical Presentation
The classic diagnostic triad includes:
- History of cesarean section or gynecological surgery 4
- Cyclical pain and swelling at the scar site (present in 93.8% of patients), with symptoms waxing and waning with the menstrual cycle 1, 4
- Palpable mass within or near the surgical scar 2, 4
Additional clinical features:
- Mean presentation occurs 4.56 years after the index surgery 1
- Mean age at diagnosis is 35-38 years 1, 3
- Mean lesion size is 2.84 cm 1
- Concurrent pelvic endometriosis occurs in 18.9% of cases, warranting consideration of diagnostic laparoscopy in symptomatic patients 1, 3
Diagnostic Approach
Diagnosis is primarily clinical, based on the characteristic triad of prior surgery, cyclical scar pain/swelling, and palpable mass. 2, 4
Imaging
- Ultrasound is the initial imaging modality to characterize the nodular lesion and rule out other pathology 5
- Imaging reveals characteristic nodular lesions with features consistent with endometriosis 5
Tissue Diagnosis
- Fine needle aspiration cytology (FNAC) can confirm diagnosis preoperatively and exclude malignancy, though its role remains somewhat controversial 2, 5
- FNAC is particularly useful in patients without a palpable painful mass 2
- Histopathology may show fibrosis as an important component, and absence of classic endometrial glands does not exclude the diagnosis 4
Critical pitfall: Scar endometriosis can mimic carcinoma clinically, making tissue diagnosis important when the presentation is atypical 5
Management
Surgical Treatment (Definitive)
Complete wide surgical excision with histologically proven free margins of at least 1 cm is the treatment of choice and mandatory to prevent recurrence. 3
Surgical principles:
- Excision must include adjacent fascia, subcutaneous tissue, and skin to ensure complete removal 2
- All patients should have involvement of subcutaneous tissue assessed, with rectus sheath involvement common (occurring in 11 of 16 patients in one series) 1
- Consider exploratory laparoscopy in symptomatic patients to exclude intraperitoneal disease, given the 18.9% rate of concurrent pelvic endometriosis 1, 3
Outcomes
- No recurrence was observed in patients who underwent complete excision during mean follow-up of 11.91-34.6 months 1, 3
- Local recurrence (rare) and pelvic recurrence can occur if margins are inadequate 3
- Resolution of symptoms is expected following complete excision 5
Medical Treatment
Medical therapy alone is not recommended as primary treatment for scar endometriosis, as it does not address the localized mass 2
However, selective medical treatment may be considered:
- Postoperatively in cases with concurrent pelvic endometriosis 2
- The role of postoperative medical management to reduce recurrence requires further prospective study 1
Prophylactic Measures
Prevention during cesarean section and pelvic surgery should focus on avoiding decidual/endometrial contamination of the wound: 2
- Change gloves and instruments after uterine closure
- Irrigate the surgical field before closing the abdominal wall
- Avoid using the same sponges that contacted the endometrium on the abdominal incision