Purpose of the study: Echinococciasis or hydatid disease is a cosmopolite antropozoonosis common to humans and several mammal species. The disease results from the development of the larval or hydatid form of the canine tenia (Echinococcus granulosis) in the organism. Hydatic cysts are uncommonly found in muscles, even in endemic zones. The purpose of this work was to describe the epidemiological, clinical and therapeutic aspects of hydatid cysts observed in muscles based on our clinical experience and data in the literature.
Material and methods: For this study, we collected data on eleven cases of hydatid cysts in muscles treated surgically at the Sousse University Hospital in Tunisia over a 17-year period from 1985 to 2002. We noted epidemiological, clinical, ultrasonographic and laboratory data which were analyzed to better detail the characteristic features of these localizations.
Results: Mean patient age was 30 years (range 7-50). All patients lived in rural areas where sheep raising and contact with dogs was common. Patients consulted for a tumefaction of the soft tissue which increased in volume progressively. The muscle focus was generally unique and primary. The proximal muscles of the limbs were involved predominantly. Ultrasonography was performed for nine patients and suggested the diagnosis in all cases. The typical feature was a liquid echostructure in an endemic context. Computed tomography was performed in four patients with deep cysts. Magnetic resonance imaging was not used. Surgical treatment was used in all cases with a pericystectomy in six. Early outcome was favorable excepting one case of suppuration of the resection zone observed in one woman. At 2.5 years, there have been no cases of local or distant recurrence.
Discussion: Several factors would explain the exceptional nature of muscle localizations of hydatid cysts: efficacy of the hepatic and pulmonary barriers, muscle environment not favorable for growth of hydatid larvae. The predominant localization in the proximal muscles of the lower limbs could be explained by the volume of the muscle mass and its rich blood supply. It is important to establish the diagnosis preoperatively in order limit the risk of anaphylactic shock or dissemination in the event of puncture or accidental opening of the cyst during resection. Ultrasonography is the diagnostic tool of choice. Surgery is required for treatment, ideally by en bloc total pericystectomy. Medical treatment with imidazoles has little efficacy for the treatment of muscular hydatid disease.
Conclusion: Hydatid cysts are rarely found in muscles, even in highly endemic zones. The diagnosis must nevertheless be entertained depending on the clinical and endemic context. Ultrasonography, and accessorily magnetic resonance imaging, are the exploration tools of choice to confirm the diagnosis before surgery and avoid puncture. Exclusively surgical treatment is indicated, ideally for total pericystic resection without rupture.