Scar Endometriosis
Definition
Scar endometriosis is the presence of functional endometrial glands and stroma within or adjacent to a surgical scar. It is a form of secondary abdominal wall endometriosis, most often occurring after a lower-segment caesarean section (LSCS).
Etiopathogenesis
Usually due to iatrogenic implantation of endometrial tissue into the wound during uterine surgery. Under hormonal stimulation, these implanted cells proliferate and bleed cyclically.
Common preceding procedures
- Caesarean section, most common
- Hysterotomy or laparotomy
- Laparoscopy port sites
- Episiotomy scar, rarely
A 2025 systematic review found that
64% to 96% of reported scar endometriosis cases followed caesarean delivery (
review abstract).
Clinical features
- History of previous caesarean or pelvic surgery
- Painful swelling/nodule in or near the scar
- Cyclical pain and increase in size/tenderness during menses, the classical presentation
- Mass may be firm, fixed, pigmented or occasionally bleed
- Symptoms can begin months to years after surgery
- May coexist with pelvic endometriosis, though not always
Abdominal wall implants classically present as a discrete, cyclically painful abdominal mass. Berek & Novak's Gynecology, p. 577.
Sites
- Pfannenstiel incision scar
- Midline laparotomy scar
- Umbilicus
- Laparoscopic port scar
- Episiotomy scar
Lesions may involve skin, subcutaneous tissue, rectus sheath, rectus muscle, parietal peritoneum, or rarely extend intra-abdominally.
Differential diagnosis
- Incisional hernia
- Suture granuloma
- Lipoma
- Abscess
- Hematoma
- Keloid
- Desmoid tumour
- Soft-tissue sarcoma
- Sister Mary Joseph nodule
Diagnosis
Diagnosis is mainly clinical, based on the triad of:
- Previous uterine/pelvic surgery
- Scar mass
- Cyclical pain
Investigations
- Ultrasonography with Doppler: first-line, shows a heterogeneous hypoechoic solid lesion with variable vascularity.
- MRI: best for defining size, depth, rectus sheath/muscle involvement and surgical planning.
- CT may be useful for extensive lesions.
- FNAC/core biopsy may demonstrate endometrial glands, stroma and hemosiderin-laden macrophages, but is not routinely essential if excision is planned. There is a theoretical risk of needle-tract implantation.
- Definitive diagnosis is histopathological after excision.
US, CT and MRI help distinguish endometriotic tissue from surrounding tissue. Fischer's Mastery of Surgery, p. 6206.
Treatment
Wide local surgical excision is the definitive treatment.
- Excise the lesion intact with about 1 cm margin of normal tissue where feasible.
- Remove involved fascia/muscle/peritoneum if necessary.
- Large fascial defects may require mesh repair.
- Send specimen for histopathology to confirm diagnosis and exclude rare malignant transformation.
Medical therapy with combined oral contraceptives, progestins, dienogest or GnRH analogues may temporarily reduce pain/size, but does not eradicate the lesion and symptoms commonly recur after stopping treatment. It may be considered when surgery is unsuitable or as adjunct treatment.
Wide excision with a 1-cm margin is recommended to limit recurrence. Fischer's Mastery of Surgery, p. 6206.
Complications
- Recurrence after incomplete excision
- Large abdominal wall defect after radical resection
- Rare malignant transformation, usually clear-cell carcinoma
Prevention during caesarean section
- Avoid contamination of wound by endometrial tissue
- Exteriorize uterus where appropriate
- Change gloves/instruments after uterine closure
- Thorough irrigation of wound before abdominal-wall closure
- Careful closure of uterine and abdominal-wall layers
Key exam point: A woman with a painful nodule in a previous LSCS scar, particularly with cyclical exacerbation during menstruation, should be considered to have scar endometriosis until proved otherwise.