Hook-wire insertion facilitates the excision of scar endometriosis


  • ML Hull,

    Corresponding author
    1. Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia
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  • MT Gun,

    1. Department of Radiology, The Queen Elizabeth Hospital, Woodville, South Australia, Australia
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  • M Ritossa

    1. Department of Obstetrics and Gynaecology, The Lyell McEwin Hospital, Elizabeth Vale, South Australia, Australia
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Dr ML Hull, Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, Faculty of Health Sciences, 6th Floor, Medical School North, University of Adelaide, Adelaide 5005, Australia. Email louise.hull@adelaide.edu.au

Case 1

A 28-year-old woman was referred with continuous, superficial, right-sided abdominal pain in her caesarean section scar that had initially occurred cyclically with menstruation. Her history included four caesarean deliveries. She had also had three laparoscopies for pelvic pain. These procedures revealed several pelvic endometriotic lesions that were diathermied or excised intraoperatively. A Mirena intrauterine contraceptive device had been inserted at the time of her last laparoscopy and she was amenorrhoeic.

On examination, a tender palpable mass was detected 1 cm above the right edge of her pfannsteil scar. Sonographic evaluation of this site revealed an irregularly shaped 2.2 × 1.1 cm area of reduced echotexture 3 cm below the skin, which was likely to represent an endometriotic lesion. This lesion involved the fat layer and did not extend through the rectus sheath.

When an excisional operation was performed, the surgeon was unable to localise this subcutaneous mass, although the skin had been marked preoperatively. The excised histological specimen demonstrated only fibrotic tissue. At a subsequent clinic appointment, the woman’s pain had not resolved and the abdominal wall lesion was still present on ultrasound examination.

A further operative procedure was undertaken and, on this occasion, a hook-wire was inserted preoperatively. This was placed through the pfannensteil scar into the hypoechoic mass using ultrasound guidance and local anaesthesia. A small incision was made in the caesarean section scar adjacent to the hook-wire. Diathermy was used to dissect down to the endometriotic lesion following the hook-wire. The lesion was excised intact with adequate margins and a small defect in the rectus sheath was repaired by primary closure. Histology confirmed the presence of endometrial glands and stroma in this specimen. The woman made a full recovery and her abdominal wall pain had completely resolved at a visit 8 weeks later.

Case 2

A 34-year-old woman presented with a 5-year history of a painful lump in the left inguinal region below a pfannsteil caesarean section scar. This pain was exacerbated by menstruation every 30–35 days in a natural menstrual cycle. Two scans had previously revealed a circumscribed 3 × 1 cm hypoechoic lesion in the left anterior abdominal wall. The diagnosis of an endometriotic lesion was confirmed when brown-stained fluid was aspirated with a fine needle. Prior to referral, there had been one unsuccessful attempt at surgical removal of this subcutaneous endometriotic lesion. This woman did not have a history of endometriosis but had had two previous caesarean sections.

Before excisional surgery, a hook-wire was placed through the scar and into the endometriotic tissue using ultrasound guidance. After opening a small portion of the pfannsteil scar, the lesion was identified by dissecting along the path of the hook-wire. This lesion was then resected with wide margins and primary closure of the sheath was performed. Follow-up histology showed that the endometriotic lesion had been excised in full. This woman’s period-associated abdominal pain had resolved at a subsequent clinic appointment.

Case 3

A 37-year-old woman was seen suffering from dysmenorrhoea, menorrhagia and subumbilical tenderness. She had a history of three caesarean section deliveries. A laparoscopy had been performed 4 years earlier, and at this operation, endometriotic lesions had been identified in the ovarian fossa and pouch of Douglas. This woman was initially treated medically with gestrione for 6 months. However, her symptoms only resolved after subsequent insertion of an Implanon Implant (68 mg etonogestrel; Organon, OSS, The Netherlands) contraceptive device during an 18-month period of amenorrhoea. Her abdominal wall and pelvic pain symptoms recurred when she started to bleed lightly per vaginum with the Implanon Implant in situ and she was referred to our care.

Although a mass was not palpated, examination did reveal a localised tender area below the umbilicus. An ultrasound of the anterior abdominal wall revealed a hypoechoic lesion (1 × 1 cm) with an endometrioma-like appearance, positioned in the subcutaneous fat immediately inferior to the umbilicus.

Prior to operative excision, a hook-wire was inserted under ultrasound guidance into the subumbilical mass through the previous laparoscopy scar. At operation, an incision was made in the subumbilical scar and tissue was dissected away from the hook-wire until the endometriotic lesion was identified above the rectus sheath. The endometriotic tissue was removed with wide margins. A small defect in the rectus sheath was oversewn. This procedure was followed by a total laparoscopic hysterectomy and endometriosis was not visually identified in the pelvis. The diagnosis of abdominal wall endometriosis was confirmed histologically with the identification of completely excised endometrial glands and stroma. This woman’s subumbilical pain had completely resolved at a follow-up appointment.


Endometriosis is defined by the presence of endometrial glands and stroma outside the uterine cavity. Approximately 10–15% of reproductive aged women suffer from endometriosis,1 with lesions occurring most commonly in the pelvic cavity.2 Sampson’s theory3, that endometriosis arises when endometrial tissue in menstrual fluid travels in a retrograde fashion through the fallopian tubes and implants in the pelvis, is widely supported.

Subcutaneous endometriosis is rare and almost always associated with previous surgery. Khammash et al. have estimated a 0.2% incidence of scar endometriosis after caesarean section. This figure was reached by dividing the number of women with caesarean section scar endometriosis by the number of women with caesarean sections over the same 5-year period in two hospitals in Irbid, Jordan.4 Subcutaneous endometriotic tissue has also been described in laparoscopic port site scars.5 In our case series, two women had endometriotic lesions in caesarean scars and the third had endometriosis in a subumbilical trocar port scar.

Most reports suggest that scar endometriosis arises when either eutopic endometrium exposed during caesarean section, or existing endometriotic tissue present in the pelvis, is directly transferred into the abdominal wall wound during an operative procedure.6,7 In this report, all three women had previous caesarean deliveries, of these two were diagnosed as having pelvic endometriosis prior to the development of scar endometriosis.

The sonographic features of subcutaneous endometriosis are a hypoechoic cystic space containing scattered hyperechoic echoes with irregular margins that infiltrate the adjacent tissues surrounded by a hyperechoic ring of variable width and continuity.8 In this series, ultrasonographic findings pointed to a likely diagnosis of subcutaneous endometriosis in all cases. Colour Doppler was not required to identify the endometriotic lesions, although its use has been reported in the literature.8 Fine-needle aspiration9 has also been used diagnostically in cases of incisional endometriosis and this was an useful diagnostic aid in our second case.

Surgical excision is the treatment of choice for scar endometriosis.7,10 Case reports allude to the difficulties that can be encountered in identifying and completely removing subcutaneous endometriosis at operation. One case series described two women who did not have resolution of their scar pain following excision of scar endometriosis.7 This implies that subcutaneous endometriomas are not always identified and removed during excisional procedures. Mesh repair of the rectus sheath following excision of incisional endometriosis has also been reported.9 This suggests that large amounts of tissue may be removed to ensure complete resection of subcutaneous endometriotic tissue. In our series, surgeons were unable to localise endometriotic lesions when the hook-wire was not used, even when preoperative skin markings were made over the palpable mass.

Before the decision to use a hook-wire is made, variables, such as endometriotic lesion size, the depth of lesion, body habitus and whether the lesion is palpable, need to be assessed. In this series, all endometriotic lesions were less than 4 cm in diameter and situated deeply in the subcutaneous fat and two of three lesions were not palpable. Lesions of this nature are likely to be hard to locate at surgery, and in such cases, hook-wire insertion provides a specific method for intraoperative lesion identification.

Hook-wires (see Figure 1) have been used to localise breast10 and lung11 lesions prior to diagnostic biopsy or excision. Hook-wire insertion is safe and causes minimal discomfort when carried out under local anaesthesia. When deployed, the hook-wire is difficult to dislodge, ensuring specific localisation of the subcutaneous endometriotic lesion and necessitating the inclusion of the hook-wire, with the histology specimen in all the above cases. To our knowledge, this is the first report of the use of a hook-wire to facilitate localisation and removal of subcutaneous scar endometriosis.

Figure 1.

A hook-wire and introducer.

In all three cases, removal of subcutaneous endometriotic tissue was straightforward when preoperative ultrasound-guided hook-wire insertion was carried out through an existing scar. The incision size and rectus sheath defects resulting from these operations were small, the rectus sheath being easily repaired with primary closure in all cases. Histology confirmed that the endometriotic lesions were completely excised, which resulted in resolution of the women’s symptoms. Our experience suggests that hook-wire insertion prior to operative excision significantly facilitates the removal of subcutaneous endometriotic lesions.

We advocate the use of a hook-wire to identify the site of subcutaneous endometriosis prior to excisional surgery in cases where lesions are small, deep or difficult to palpate or in situations where the surgeon has concerns regarding lesion location. We believe that this technique promotes endometriotic lesion identification and reduces the size of skin wounds and rectus sheath defects.