1. Introduction {#sec0005}
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Hydatid disease (HC) is a parasitic infestation caused by Echinococcus species. Species mainly involved include granulosus, multilocularis, and oligarthrus, with granulosus commonly responsible for cysts in predators such as dogs, wolves, and foxes as well as intermediate hosts such as sheep, goats, and cattle \[[@bib0005]\]. Humans are a coincidental intermediate host. The disease is more frequent in the Middle East, Central Europe, Australia, South America and the Mediterranean basin, where livestock breeding is very rampant. Several strains of granulosus appear to be commonly found in North America, Morocco, Tunisia, Kenya, Iraq, Iran, Kazakhstan, western China, and Argentina. Parasite larvae can develop in any part of the human body with the liver (68.8--80%) and lungs (10--22.4%), representing the most frequent localizations. Other rare localizations reported in the literature include the spleen, peritoneum, skeleton, kidney, brain, cardiac muscle and even subcutaneous \[[@bib0010],[@bib0015]\]. Muscular hydatid cysts are usually secondary in nature, resulting from migration of larvae from a primary site after spontaneous or trauma-induced cyst rupture or could even be iatrogenic after the release of parasite material during invasive treatment procedures. Primary musculoskeletal hydatid cysts are rare not to mention adductor magnus muscle hydatid cysts even in countries endemic to Echinococcus. Voluntary muscles are a very rare site of infection, counting for less than 1% of the total \[[@bib0020]\]. In line with SCARE guideline, we reported a case of adductor magnus HC \[[@bib0025]\].

2. Case presentation {#sec0010}
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A 37-year-old man, Iraqi origin, living in the rural area was admitted to our unit complaining of a slight painful swelling of the right thigh. The patient notices the swelling over about 3 weeks and was associated with recent discomfort and when he compares both thighs he notices that the right one tenser and slightly larger in diameter without fever or rigors, and pruritus. The patient did not reveal any history of trauma to his thigh or prior medication. He was afebrile on admission with good general conditions, and physical examination revealed a slight tender right upper medial side of the thigh with slight distension without any features of acute inflammation overlying skin, the overlying skin was normal. No bruit or venous hum was heard as in [Fig. 1](#fig0005){ref-type="fig"}a and b.Fig. 1(a) Comparison between thighs, deep intramuscular, slight difference appear, (b) Marked skin incision over right thigh.Fig. 1

Patient sends for an ultrasound which shows cystic lesion deep intramuscular upper medial aspect of right thigh inside the muscle as shown in [Fig. 2](#fig0010){ref-type="fig"}. Routine blood investigations, we also performed abdominal US, chest X-ray, and cranial MRI in order to rule out any involvement of the body. All imaging studies detected no other cyst in other parts of the body. So the hydatid cyst in the adductor magnus muscle in our patient assumed to be primer muscle hydatidosis. Then Magnetic resonance Imaging (MRI) depicted a unilocular cyst without septations deep inside adductor magnus muscle about 100 × 65 mm, Serology for Echinococcus by ELISA (Ridascreen Echinococcus IgG; R-Biopharm, Darmstadt, Germany) was positive, measuring 2.5 IU (cut-off \>1.1). Based on these findings, a diagnosis of hydatid cyst was performed. MRI features were suggestive of hydatid cystic mass without infiltrating bone nor surrounding neurovascular structures as in [Figs. 3](#fig0015){ref-type="fig"}a, b and [4](#fig0020){ref-type="fig"} ). Patient was prepared for elective surgery with consent and anthelminthic therapy was initiated preoperatively for 5 days, Incision done over site of location of the cyst until reach the adductor magnus muscle the care was taken to avoid spillage, 10% Betadine soaked mops were placed around the cyst suction tube nearby and needle aspiration of clear fluid then the injection of scolicidal agent cetrimide (1.5%) instilled in it as in [Fig. 5](#fig0025){ref-type="fig"}. Wait 5 min then incision on cyst did, through meticulous pericystectomy along surrounding muscle fibers [Fig. 5](#fig0025){ref-type="fig"}a and b. The cyst was unilocular containing clear fluid, after the aspiration process, cetrimide solution was applied into the cavity and irrigation was performed with isotonic saline. Finally, the drain was fixed and the tissues were repaired. The diagnosis of a hydatid cyst was confirmed with macroscopic and microscopic histopathological examinations after removal of the mass as in [Fig. 6](#fig0030){ref-type="fig"}, [Fig. 7](#fig0035){ref-type="fig"}. Albendazole treatment was continued for three months postoperatively with 15 mg/kg/d.Fig. 2Ultrasound picture show cystic mass deep intramuscular.Fig. 2Fig. 3(a) MRI picture cross-sectional view thigh show adductor magnus cystic mass, (b) MRI cross-sectional view upper thigh show cystic mass.Fig. 3Fig. 4MRI coronal plane show cystic mass in adductor muscle of right thigh.Fig. 4Fig. 5(a) Scolicidal injection, (b) Pericystectomy of cyst.Fig. 5Fig. 6Histological view hydatid cyst (Hematoxylin & Eosin stain ×200.Fig. 6Fig. 7Whole cyst completely excised.Fig. 7

3. Discussion {#sec0015}
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Primary skeletal muscle hydatid cyst is very rare because implantations at this site require passage through the filters of the liver and lung. In addition, the intramuscular growth of cysts is hindered by muscle's contractility and lactic acid content \[[@bib0030]\]. The patient with muscular echinococcosis should

be evaluated in order to determine whether there is another focus of dissemination since the disease is generally located in other parts of the body especially hepatic and pulmonary regions \[[@bib0030],[@bib0035]\]. We excluded the other organ involvement by the careful clinical and radiological examination of the patient, and the localization in the adductor magnus muscle was therefore assumed to be primer muscle hydatidosis. Diagnosis of human echinococcosis remains highly dependent on imaging techniques to detect the cystic space occupying lesion \[[@bib0035]\]. US is particularly useful in the diagnosis of hydatid cyst when the daughter cysts and hydatid sand are demonstrated \[[@bib0040]\]. However, in muscular hydatid cyst, the US findings are sometimes indistinguishable from those of soft tissue abscess leading to misdiagnosis \[[@bib0045],[@bib0050]\]. Computed tomography has an advantage over ultrasound for better documentation of site, size, and structure of cyst. MRI may show an intense rim which has been proposed as a characteristic sign of hydatid disease \[[@bib0040]\]. Serologic tests are then typically used to confirm the diagnosis. Indirect immunofluorescence antibody test, ELISA, immunoelectrophoresis, and immunoblot test are the commonly used techniques \[[@bib0055]\]. In our case, the diagnosis was established by radiological, serological and histopathological examinations. The treatment of human muscle hydatidosis is principally surgical; however, the cysts' contents spillage may occur during the surgery resulting in anaphylaxis and/or secondary echinococcosis \[[@bib0060]\]. It is widely believed that the higher lactic acid concentration in skeletal muscle and mechanical factors, such as contractions make implantation of cyst less likely. The most common musculoskeletal sites include pelvic, thigh, and paravertebral musculature \[[@bib0065]\]. Another compatible hypothesis is one of a spontaneous resolution of primitive hepatic localization but with the systemic diffusion of the parasite and positivity of serological exams \[[@bib0070], [@bib0075], [@bib0080]\]. Diagnosis is based on clinical evidence such as anamnestic data pertaining to origin and history of exposure to livestock, presentation as well as radiological backing. Hydatid serology is often negative in 1 out of 2 cases of extrahepatic hydatid disease as was the case in our patient. In general, MRI has a higher specificity and sensibility than ultrasound for hepatic hydatid cyst \[[@bib0085]\]. It also allows a better characterization of anatomical relations and aids surgical management of cyst as was the case in our patient. It is essential to establish the definitive preoperative diagnosis of skeletal muscle hydatid cysts. This contraindicates certain treatment options like marginal excision or incisional biopsy due to the likelihood of dissemination and anaphylactic shock on spillage. Thursky et al. \[[@bib0090]\] Pericystectomy remain the treatment of choice in musculoskeletal hydatid cysts. Percutaneous aspiration, infusion of scolicidal agents like chlorhexidine gluconate, and re-aspiration (PAIR), under imaging (ultrasound or CT) guidance, can be used as an alternative to surgery in inoperable cases. Ormeni et al. \[[@bib0095]\] Supplementary chemotherapy with anthelminthic for skeletal muscle hydatid disease are controversial and currently, no evidence provides sufficient backing on the benefit of its association with conservative treatment. Albendazole remains the gold standard drug administered in adjuvant therapy. Hydatid cystic disease has a nonspecific clinical course and symptoms depend on its localization and size. It is usually presents as painless, non-inflammatory mass \[[@bib0100]\]. Proper history taking, knowledge about endemics and risk factors and using variety of diagnostic methods such as US, MRI, CT, ELISA tests or hematological tests are important for the diagnosis of cases with muscular findings.

4. Conclusion {#sec0020}
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Hydatid cyst should be considered in intramuscular cystic mass especially in the endemic region, Preoperative diagnosis is important in the management of hydatid cyst. Pericystectomy the best choice combined with neoadjuvant therapy could help reduce complications and recurrence in large deep intramuscular hydatid cysts.

Conflicts of interest {#sec0025}
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No any conflicts of interest.

Funding source {#sec0030}
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Non funding.

Ethical approval {#sec0035}
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The study is exempt from ethical approval in my institution.

Consent {#sec0040}
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Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Author contribution {#sec0045}
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I am only the contributory author for this my case report.

Registration of research studies {#sec0050}
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Researchregistry 4351.

Guarantor {#sec0055}
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I am only responsible, no other than me.

Provenance and peer review {#sec0060}
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Not commissioned, externally peer-reviewed.
