Case Presentation
A 23-year-old woman presented with 4 months’ duration of a painful mass in a Pfannenstiel incision. She had undergone a cesarean section 4 years earlier. The patient reported that the mass was more obvious and painful on straining and during menses. Physical examination showed that she had a well-healed Pfannenstiel incision. A 2-cm mass was palpable on the left lateral end of the incision and became more prominent with straining. The differential diagnosis for a swelling in a Pfannenstiel incision included incarcerated hernia, fat necrosis, and scar endometriosis.

The patient underwent elective laparoscopy. Findings were normal and in particular did not reveal any evidence of incisional or inguinal hernias or pelvic endometriosis. The mass, which was in the subcutaneous plane and free from the underlying anterior abdominal fascia, was excised. The patient had an uneventful recovery (Figure 1). Pathologic analysis of the mass was consistent with endometriosis (Figure 2).

Discussion
Endometriosis occurs in approximately 2% to 10% of women of childbearing age.¹ Endometriosis is defined as an aberrant or heterotopic growth of glands and stroma outside the uterus that is identical to the uterine lining. Endometriosis usually occurs in the pelvic cavity and presents with cyclic pain at the time of menstrual periods. It accounts for one third of cases of chronic pelvic pain in women and can cause secondary dysmenorrhea, deep dyspareunia, menorrhagia, and infertility. Endometriosis outside the pelvic cavity is extremely rare, and hence infrequently encountered by general surgeons.

Endometriosis located in a surgical scar is an unusual complication. The incidence of scar endometrioma resulting from cesarean section is 0.1%, and approximately 25% of women with this condition have concomitant pelvic endometriosis.²

Endometrioma is most often manifested as a nodule in a previous abdominal incision, usually in a Pfannenstiel incision. Endometriomas have been seen in the form of abdominal wall tumors, umbilical nodules, and inguinal canal swellings. They have also been reported to cause terminal ileal obstruction and present with rectal bleeding. They can be identified incidentally in appendectomy specimens.

A cyclic increase in pain, swelling, and bleeding from a skin or soft-tissue nodule is helpful for the diagnosis. These symptoms are extremely rare but clinch the diagnosis if present. Cyclic bleeding does not occur in any other condition, aside from menstruation. Scar endometrioma most often presents as an abdominal mass with noncyclic pain.³ Endometriosis should be considered in the differential diagnosis of incisional abnormalities in any woman of childbearing age. This disorder is almost always secondary to an invasive gynecologic procedure, such as a cesarean section or a hysterectomy, although it could occur de novo.⁴ The onset of sym­ptoms varies; it may occur up to several years after surgery.⁴ Some experts recommend extensive diagnostic workup that includes ultrasound⁵ and computed tomography studies as well as needle biopsy.

Treatment is not required in asymptomatic patients. Surgical excision is both diagnostic and curative⁶ and is the treatment of choice in all patients; it can even be done using local anesthesia, if needed. To prevent abdominal wall endometrioma after cesarean section, thorough cleaning of the abdominal wound with high-jet saline solution before closure is recommended.⁷

Medical treatment involves the hormonal suppression of ovulation for a period of 6 to 12 months to allow the lesions to atrophy. This can be done using danazol or gonadotropin-releasing hormone (GnRH) agonists. The chronic administration of GnRH agonists produces a “medical oophorectomy.” Medical management is associated with significant adverse effects as well as a high risk of recurrence after therapy is stopped.

Conclusion
Endometriosis located in a surgical scar is an unusual complication. It is almost always preceded by a cesarean section or hysterectomy performed several years earlier. High-jet saline solution irrigation of the wound at the time of cesarean section has been recommended as a preventive measure. Although extensive diagnostic workup has been described, surgical excision itself is both diagnostic and curative.

References
1. National Institute of Child Health and Development. Endometriosis. Rockville, Md: US Department of Health and Human Services, National Institutes of Health; September 2002. NIH publication 02-2413. Available at www.nichd.nih.gov/publications/pubs/endometriosis.pdf

2. Wolf Y, Haddad R, Werbin N, et al. Endometriosis in abdominal scars: a diagnostic pitfall. Am Surg. 1996;62:1042-1044.

3. Blanco RG, Parithivel VS, Shah AK, et al. Abdominal wall endometriomas. Am J Surg. 2003;185: 596-598.

4. Gunes M, Kayikcioglu F, Ozturkoglu E, et al. Incisional endometriosis after cesarean section, episiotomy and other gynecologic procedures. J Obstet Gynaecol Res. 2005;31: 471-475.

5. Alexiadis G, Lambropoulou M, Deftereos S, et al. Abdominal wall endometriosis—ultrasound research: a diagnostic problem. Clin Exp Obstet Gynecol. 2001;28:121-122.

6. Daye SS, Barone JE, Lincer RM, et al. Pfannenstiel syndrome. Am Surg. 1993;59:459-460.

7. Wasfie T, Gomez E, Seon S, et al. Abdominal wall endometrioma after cesarean section: a preventable complication. Int Surg. 2002; 87:175-177.