Review
Clinical and imaging features of abdominal wall endometriomas Kylie Edwards, FRANZCOG, MBBS1,2 DDU2,3
, Shih-Han Tsai, MRANZCOG, MBBS3 and Alka Kothari, FRANZCOG, MD,
1
Bundaberg Hospital, 271 Bourbong Street, Bundaberg, Queensland, 4670, Australia The University of Queensland, St Lucia, Queensland, 4072, Australia 3 Redcliffe Hospital, Anzac Avenue, Redcliffe, Queensland, 4020, Australia 2
Abstract Abdominal wall endometrioma (AWE) is a rare condition (incidence 1% following caesarean section) with a significant variation in clinical symptoms, imaging findings and interval between initial procedure and diagnosis. We present two cases with differing clinical presentations. AWE may be difficult to diagnose pre-operatively, with as many as 75% of lesions diagnosed incorrectly prior to surgical excision. Ultrasonography is a useful tool in determining the extent of the endometrioma and can help exclude differential diagnosis such as hernia. Ultrasound appearance of AWE is often variable; however, the most common presentation is of a solid hypoechoic mass lesion with peripheral vascularity. Margins may be irregular and infiltrate the surrounding soft tissues. Lesions may be cystic or multicystic or may have both solid and cystic components. Power Doppler may demonstrate internal vascularity. If ultrasound findings are inconclusive, computed tomography (CT) or magnetic resonance imaging (MRI) should be considered to assist in making the diagnosis. Ultrasound-guided fine needle aspiration of the lesion may assist in the diagnosis, but seeding of the needle tract has been reported and must be included in the resection margins. Sonoelastography has shown some promise in early studies for improving diagnostic accuracy for AWE. Keywords: abdominal wall, biopsy-fine needle, elasticity imaging techniques, endometriosis, ultrasonography.
Introduction Endometriosis of the abdominal wall is a rare complication of caesarean section and other gynaecological surgeries.1 It may present as a discrete lesion (abdominal wall endometrioma) in association with a surgical scar, usually following a procedure requiring incision into the uterine cavity.1,2 While it commonly presents as a painful, palpable mass that correlates to the menstrual cycle, the presentation can be variable, making diagnosis difficult.3 The time interval between the initial surgery and the presentation with clinical symptoms can also be highly variable and may be between 3 months to 10 years4. Ultrasound findings can likewise be highly variable. We present two cases of abdominal wall endometrioma (AWE) with differing presentations. Case 1 A 25-year-old woman presented to the gynaecology clinic twelve months following a caesarean section for placental abruption at 34 weeks gestation. She had a history of pain in Correspondence to email
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the area of the caesarean scar that commenced 6 months after the operation. The pain was localised to the right side of the scar and was only present at the time of menstruation. A small lump was also noted in the area when the pain was present. Her cycles were regular, and she was not on hormonal contraception. She had no other surgical procedures or medical issues. On examination, a palpable mass measuring 2 cm was noted anterior to the right side of the caesarean scar. An ultrasound of the abdominal wall confirmed a 26 9 13 9 21 mm hypoechoic mass with some internal vascularity on the right aspect of the caesarean section scar. Based on the clinical history and the ultrasound findings, a diagnosis of AWE was made and she was booked for a surgical excision of the mass (Figures 1 and 2). At the time of the operative procedure, a 30 9 20 mm mass, which involved the rectus sheath, was excised. The rectus sheath was closed without requiring a mesh. The external appearance of the excised tissue was of fibrofatty tissue and sectioning revealed areas of both fibrosis and haemorrhage. Microscopic examination confirmed an endometrioma. The patient was reviewed at 6 weeks and was discharged with no further complaints. © 2018 Australasian Society for Ultrasound in Medicine
Features of abdominal wall endometrioma
Figure 1: Ultrasound Image of AWE, Case 1. Transabdominal Ultrasound Scan of the Inferior Umbilical Region Depicting an Ill-defined, Hypoechoic Lesion in the Subcutaneous Tissue Measuring 2.1 9 1.3 cm.
Figure 2: Ultrasound Image AWE, Case 1. Transabdominal Colour Doppler Image Displaying a Small Amount of Internal Vascularity Within the Lesion.
Case 2 A 42-year-old lady presented to the outpatient clinic with a one-month history of intermittent left-sided lower quadrant pain. The pain was colicky in nature and could last for several days. It was associated with irregular bowel motions but was not related to her menstrual cycle. Her cycles were regular and associated with mild dysmenorrhoea. Her medical history included depression and morbid obesity. She had a laparoscopic banding procedure done and successfully lost 40 kg. Previously, she had two caesarean sections, five and 8 years prior © 2018 Australasian Society for Ultrasound in Medicine
to her presentation. She was not using any hormonal contraception at the time of presentation. No mass or tenderness was elicited at the first presentation. A pelvic ultrasound scan was performed but was inconclusive and a probable bowel cause for the pain was suggested. The patient was reviewed 3 months later, still complaining of ongoing left iliac fossa pain despite normal bowel function. The pain was now reported to be worse during menstruation and exacerbated by movement. On examination, a 2–3 cm hard, tender mass was palpated superior to the caesarean scar on the left side with bruising noted on the overlying skin. The mass was not reducible. An ultrasound of the area showed a 32 9 27 9 32 mm illdefined and irregular hypoechoic area with no increased vascularity. A CT scan confirmed an irregular lesion inseparable from the lateral aspect of the left rectus abdominis muscle. At this stage, a provisional diagnosis of AWE was made (Figures 3–6). The patient proceeded to a surgical excision of a 5 cm lesion from the anterior abdominal wall and rectus sheath. A 4 cm defect in the rectus sheath was closed using a mesh. Macroscopic inspection showed a 6.0 9 4.0 9 4.0 cm of fibroadipose tissue with one smooth fibrous surface. On sectioning, adipose and fibrous tissues were seen with a central area of cavitation and focal haemorrhage 3.5 9 3.0 9 1.3 cm in size. Microscopic examination was confirmatory of endometriosis with involved margins. She was discharged on the second day and had complete resolution of the symptoms at the 8-week post-operative review (Figures 7 and 8). Discussion Abdominal wall endometrioma is a diagnosis that is made with difficulty, clinically and radiologically. It is most commonly seen in the setting of prior uterine surgery, usually following a caesarean section or hysterotomy.1,2 Variable incidence of AWE has been reported in different studies, but appears to be up to 1%.2,3,5 The most commonly accepted theory of the cause of AWE is the transport theory. This theory suggests that direct inoculation or transport of the endometrial tissue into the surgical scar or adjacent tissue during the surgery is responsible for AWE. A second explanation is the metaplasia theory, which suggests that primitive mesenchymal cells may undergo metaplasia to form endometrial implants resulting in AWE.6,7 The patient typically presents with a palpable erythematous skin nodule or mass associated with a previous surgical incision site – usually a caesarean section, hysterectomy, or other gynaecologic or obstetric procedure. The mass usually causes intermittent pain, tenderness and enlargement that may correlate with the menstrual period. The hormonal influences may also cause cyclic cutaneous bleeding and associated bruising of the mass.6,8,9 Concomitant pelvic endometriosis may occur in up to 14% of patients10, leading to dysmenorrhoea or menstrual irregularities. AJUM February 2018 21 (1)
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Figures 3 and 4: Ultrasound Image of AWE, Case 2. Transabdominal Ultrasound Scan of the Left Groin Demonstrating an Ill-defined Hypoechoic Lesion Measuring 3.2 9 2.7 9 3.2 cm.
Clinical examination may reveal a painful swelling close to the scar, with a history of worsening symptoms on coughing, and exertion, causing it to be confused with post-operative hernia, although, unlike a hernia, an AWE should not be reducible.11 One method of differentiating between an AWE and a hernia or other intra-abdominal mass is to ask the patient to elevate their head while in the supine position. An abdominal wall mass may become more fixated, whereas an intra-abdominal mass would become less prominent with this manoeuvre.12 Accurate pre-operative diagnosis of AWE can be challenging and requires a high index of suspicion due to the non-specific clinical presentation and a wide range of differential diagnoses, including abscess, incisional hernia, haematoma, lipoma, suture granuloma, sarcoma, desmoid tumour, lymphoma and primary or metastatic malignant lesions.13 Ultrasonography, CT and MRI are used for pre-operative evaluation of these lesions. They may also help delineate the extent of the disease. Ultrasound is usually the first imaging modality performed to diagnose abdominal wall masses. It is particularly useful for excluding hernia and determining the size of the lesion.11 Ultrasound appearance of AWE is variable. The most common appearance is a solid, non-homogenous, hypoechoic mass.14,15 Lesions with a more fibrotic component may show echogenic strands or spots and those that are currently haemorrhagic may show cystic changes representing small blood lacunae.14,15 If the AWE has infiltrated the surrounding tissue, the border may appear irregular or spiculated. Alternatively, an inflammatory reaction from the surrounding area may result in a hyperechoic border. More than one lesion may be present within the abdominal wall incision site.13 Most AWE examined with colour Doppler will demonstrate vascularity, which is usually peripheral, appearing as either a 26
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single pedicle or as multiple feeding vessels. If power Doppler is used, internal vascularity may be seen due to the higher sensitivity of this modality for small, low-velocity vessels.13 If the diagnosis remains uncertain despite clinical assessment and ultrasound, a CT scan or MRI may be considered. Like USS, CT findings can be non-specific but most commonly appear as a solid soft-tissue mass. Attenuation varies, with hyperattenuation the most common finding. Due to the vascular nature of AWE, feeding vessels may be seen as well as mildto-moderate enhancement with contrast.13 MRI characteristically shows a heterogenous, usually hyperintense, area on both T1- and T2-weighted images. MRI may be preferable as it offers improved tissue characterisation and is non-radiating compared to CT scan.13 If further workup is required, fine needle aspiration under ultrasound guidance can be performed. Needle tract endometriosis has been reported, so the site of aspiration should be included in any resection performed.13 Real-time sonoelastography (RTE) is a new sonographic/ imaging method used for the appreciation of the different tissue elasticity between diseased and surrounding tissues. It uses slight external tissue compression to quantify the strain produced in the structures examined. Through using specific software, tissue deformation is expressed as a colour variation on the ultrasound ranging from red to blue according to relative softness or hardness of the tissue.16 A pilot study using transabdominal sonoelastography to evaluate AWE was carried out by Fawzy et al.,17 on the assumption that tissue such as endometrioma with anatomo-pathological differences shows different elasticity values. Using the elastography technique, an AWE has a typical blue-green-red (BGR) appearance where the firmer borders of the endometrioma correspond to the blue area, and the softer (red and green area) correspond with the central hypoechoic areas (the anechoic © 2018 Australasian Society for Ultrasound in Medicine
Features of abdominal wall endometrioma
Figure 7: Case 2, Skin Discolouration and Mass Due to AWE.
Figures 5 and 6: CT Image AWE, Case 2. CT Scan of the Abdomen and Pelvis Showing an Irregular Soft-tissue Lesion Measuring 3.2 cm in Maximum Diameter. It is Located in the Subcutaneous Tissues of the Anterior Abdominal Wall Infiltrating the Lateral Aspect of the Rectus Abdominis Muscle.
areas visualised in the B-mode).17 The results were promising with all 23 studied patients having confirmed histo-pathological diagnosis of AWE. However, this preliminary data needs to be confirmed by larger clinical trials.17 © 2018 Australasian Society for Ultrasound in Medicine
Figure 8: Case 2, AWE at Surgery.
Surgical excision is the treatment of choice for definitive diagnosis and therapy. An intra-operative frozen section could be considered to establish the diagnosis during surgery, if there is ongoing concern as to the nature of the lesion. To prevent local recurrence, wide surgical excision with clear margins of at least 1 cm should be achieved.3,12,18 This may be difficult, however, due to the infiltrative nature of AWE. Intra-operative AJUM February 2018 21 (1)
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ultrasound has been used successfully in at least one case study19 to assist in defining the surgical margins and should be considered if difficulty is anticipated. Complete excision of the lesion may involve partial resection of the underlying fascia, which may necessitate the use of mesh repair.20 AWE should be considered in all patients who present with a surgical scar lesion, particularly if there is a cyclical component to the symptoms. Pre-operative diagnosis can be challenging due to the varied nature of the lesions, but newer modalities such as sonoelastography may help to improve the accuracy of the diagnosis. Consent Verbal consent was obtained from the patients for this publication and for the accompanying images. Competing interests The authors declare that they have no competing interests. Authors’ contributions KE was involved in the management of case 1. AK contributed to the interpretation of the ultrasound scans. KE, ST and AK compiled and approved the final manuscript and ultrasound images. References 1
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