Don’t miss it,it might be a hydatid cyst in the gluteus

Introduction

Hydatid cyst is one of the five most diagnosed zoonotic diseases in the Mediterranean region. It is endemic in Turkey, and caused by tapeworms of the genus Echinococcus. The most widespread species is Echinococcus granulosus, which usually causes a unilocular hydatid cyst. ¹ Humans are accidental intermediate hosts of Echinococcus spp. Cysts are mainly located in the liver (65%) and lungs (25%). The primary musculoskeletal involvement rate (in the absence of liver, lung or bone manifestations) remains as low as 1–5.4%. ² We here report an unusual case of hydatid cyst in the gluteus muscle to remind physicians, especially to orthopaedic oncological surgeons approaching soft tissue tumours in endemic areas.

Case report

A 36-year-old woman was admitted to our outpatient clinic with complaints of pain and limitation of movement of the right hip for 9 months. On physical examination, she had a 10 × 7 cm mobile mass on her right hip with no evidence of local inflammation. She had no history of injection, trauma or fever. Routine laboratory tests were within normal limits. Ultrasonography (USG) of the right limb revealed a 9 × 5 cm abscess in the right gluteal region. On magnetic resonance imaging (MRI), a 53 × 71 × 70 mm lesion which was hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging was seen (Figure 1a). OPEN IN VIEWER

The patient was operated upon under general anaesthesia with a pre-diagnosis of a gluteal abscess or a tumour. Through a longitudinal incision, the right gluteus maximus muscle was dissected and a cystic mass of 7 cm was totally excised (Figure 1b). Pathological diagnosis of the mass was a hydatid cyst (Figure 1c). The patient was followed uneventfully in the postoperative period. A chest radiograph and abdominal USG revealed no other hydatid cysts elsewhere. Indirect haemagglutination test for Echinococcus was positive with a titre of 1/128. Albendazole treatment at 15 mg/kg/day for a duration of 3 months was started. The patient was discharged and follow-up of the patient is still continuing with no issues.

Discussion

Echinococcus infection is endemic in our country, but intramuscular localisation is very rare. Its rareness may be explained by unsuitable conditions in the skeletal muscles for sestode larvae growth, such as high concentrations of lactic acid, and mobility of these muscles. ³ On the other hand, the large volume of the peripheral muscles and their wealthy vascularisation make this localisation attractive. ³

Administration of an anthelmintic, surgical treatment and PAIR (Puncture, Aspiration, Injection of proscolocidal agent, Respiration) are the treatment options for hydatid cyst, which mainly depend on the localisation and size of the cyst or cysts. ² In our case, since preoperative imaging studies did not support hydatid cyst, the diagnosis was made without pathological examination. Preoperative diagnosis, however, remains critical to prevent recurrences caused by the lack of preoperative anthelmintic treatment, inadvertent rupture of the cyst, and spillage of the daughter cysts and scolex. ⁴ It may, however, be hard to discriminate a mass in the gluteus from soft tissue tumours, abscess or other lesions.

Nonetheless, especially in endemic countries, hydatid cyst must be kept in mind in the differential diagnosis of cystic masses of the muscles, even though radiological imaging did not demonstrate characteristic features. In case of suspicion, preoperative diagnosis with serological tests is essential for the effective treatment with both anthelmintic therapy and surgery.