Abdominal wall endometriosis in a region distant to the caesarean section scar

Abdominal wall endometriosis (AWE) is a rare entity presenting as a painful lump with a cyclical pattern, associated with previous caesarean section (CS). AWE is typically located at the site of the CS scar. The diagnosis is challenging in the rare instance when AWE presents at a location distant to the CS scar. A 37-year-old patient presented to a general surgeon with a 2-year history of left-sided, periumbilical pain exacerbated during her menstrual periods. A 3 cm firm and tender nodule was noted clinically. Intraoperatively, the nodule involved the rectus muscle and infiltrated the peritoneum. Histology confirmed endometriosis, and the patient recovered uneventfully. The rarity of this clinical entity and the fact that AWE mostly presents to non-gynaecologists make the diagnosis challenging prolonging its physical and psychological morbidity. Thorough history-taking with emphasis on the pattern of pain and a previous history of CS should raise suspicion of AWE.

obstetrics, gynaecology and fertility; general surgery

Endometriosis is the presence of extrauterine endometrial tissue affecting 6%–10% of women of childbearing age. It usually involve the ovaries, uterosacral ligaments, pouch of Douglas, rectosigmoid colon, bladder and distal ureter.1 2 Rarely, endometriosis affects the anterior abdominal wall presenting as a palpable lesion associated with cyclical pain and history of abdominal surgery, particularly caesarean section (CS).3 All documented cases of abdominal wall endometriosis (AWE) developed at the site of the CS incision, with the exception of Egamin et al who described a case at the right lower quadrant of the abdomen, superior to the CS scar.4 In this article, we present another case of AWE in a region distant to the CS scar, this time presenting even higher, at the left periumbilical area. Case presentation A 37 year-old patient presented with a 2-year history of left-sided abdominal pain which was chronic in nature associated with acute episodes requiring prolonged hospitalisation for pain management. The pain was typically worsening during her menstrual periods and associated with a lump in the left periumbilical region. She was para 3, all delivered by CS, the last one occurring 9 years ago. There were no relevant gynaecological symptoms including dysmenorrhoea, dyspareunia or dyschezia, to suggest pelvic endometriosis. On examination, a firm nodule was palpated in the left periumbilical region (figure 1). Investigations An ultrasound scan of the anterior abdominal wall was performed which revealed a 4 cm heterogenous hypoechoic mass below the rectus sheath, involving the rectus muscle and infiltrating the peritoneum. Doppler scan did not reveal any significant vascularity (figure 2). The lesion appeared extraperitoneal but very close to the peritoneal wall. Intraoperatively, the lesion was found tethered to the peritoneal wall which had to be excised during en bloc resection. An MRI scan of the anterior abdominal wall could clarify the exact location of the lesion preoperatively5; however, we are not convinced that this would have changed the management plan. Similarly, CT could add information when ultrasound is inconclusive and MRI is not available.6 CT may be performed with or without intravenous contrast material, although the use of contrast material improves its sensitivity and specificity. In younger patients, MRI is preferred because of its improved tissue characterisation and lack of ionising radiation.6 Differential diagnosis There are different types of anterior abdominal wall lesions. The most common are desmoid tumours which account for up to 50% of the cases.7 Others include lipomas and very rarely, sarcomas (leiomysarcoma, rhabdomyosarcoma). In women of reproductive age with previous abdominal surgery (most commonly CS), AWE should be considered in the differential diagnosis. In our case, the cyclical pattern of pain prompted us to suspect AWE which was confirmed histologically. The chronic nature of the lesion and the absence of systematic symptoms of malignancy did not support a diagnosis sarcoma. Nevertheless, the surgical intent was to remove the lesion en bloc with wide margins to ensure microscopic clearance. It is important to note that AWE has also been documented in cases without preceding abdominal or pelvic surgery.5 Treatment A vertical paramedian incision was made to the left of the umbilicus as shown in figure 1, and the lesion was exposed on the rectus muscle. The lesion consisted of a dark brown central area with fibrous tissue at its periphery and was invading the full thickness of the muscle layer and tethered to the peritoneum posteriorly. En bloc resection of the lesion was performed ensuring macroscopic clearance and clear margins, and the peritoneal cavity was breeched (figure 3). Haemostasis was ensured, and the abdomen was then closed in layers without the need for a mesh. Outcome and follow-up Histological examination confirmed endometriosis. The patient was reviewed 2 and 8 weeks postoperatively and reported complete resolution of her pain. The patient was started on progestogen therapy for 3 months to reduce the risk of disease recurrence.

The aetiology of endometriosis is likely to be multifactorial with retrograde menstruation and the seeding of endometrial cells in the peritoneal cavity being one of the most established theories.8 Thereafter, an array of complex biochemical pathways contribute to the angiogenesis, vasculogenesis and inflammatory activity of endometriotic lesions.9 To date, there is no reliable biochemical marker to screen, diagnose or stage endometriosis, and diagnosis is based on more expensive and/or invasive radiological or laparoscopic procedures. This leads to diagnosis delay which often has an adverse impact on women’s physical and psychological health, and women often express a sense of relief at diagnosis.10 Despite many efforts, no single biomarker or a panel of biomarkers have been validated as diagnostic test for endometriosis.11 12 The aetiology of AWE is likely to be iatrogenic due to the seeding and inoculation of the anterior abdominal wall with endometrial cells during surgery. It is stipulated that after hysterotomy and amniotomy during CS, endometrial cells are deposited extraperitoneally in the amniotic fluid.13 In our case, although a suprapubic transverse incision was made during CS, the rectus muscle is likely to have been dissected off the rectus sheath superiorly up to the level of the umbilicus thereby optimising surgical access. This, in turn, would have made it possible for endometrial cells to be implanted on the muscle forming an endometriotic lesion significantly higher to the incision site, at the level of the umbilicus. Nonetheless, it is important to note that AWE has been documented in cases without history of abdominal/pelvic surgery.5 No aetiology has been proposed in these extremely rare cases, but it is likely to involve the same complex pathophysiological mechanisms described above.9 As demonstrated in this case, AWE can be diagnosed with a careful history and physical examination. Imaging including ultrasound and MRI can assist with localisation of the lesions and aid in surgical excision and management. Lesions that have been removed in their entirety are unlikely to reccur.5 As a team with considerable experience in managing women with endometriosis, we propose a course of adjunctive medical management after surgical excision which is found to decrease the risk of recurrence, such as medroxyprogesterone acetate 10 mg once a day for 3 months. Learning points. Good knowledge of anterior abdominal wall anatomy and the relevant pathology is essential for the general surgeon and the gynaecologist. Abdominal wall endometriosis (AWE) should be considered in any woman of reproductive age with previous laparotomy. AWE is a rare entity and typically presents with a lump at the site of the caesarean section (CS) scar. Even more rarely, it presents away from the previous CS scar, making the diagnosis challenging. Thorough history-taking with emphasis on the pattern of pain and the previous history of CS should raise the clinical suspicion of AWE. AWE is best tackled by complete excision of the lesion with wide margins and reconstruction of the abdominal wall Some cases should be managed jointly by a gynaecologist and a general surgeon. Footnotes Contributors: All authors were directly involved in the care of this patient. NG and CK were responsible for drafting the manuscript. CJ-A and MN revised and finalised the manuscript. Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. Competing interests: None declared. Provenance and peer review: Not commissioned; externally peer reviewed. Patient consent for publication: Obtained.

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