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Echinococcus is a genus of tapeworm endemic in certain parts of the world but found only rarely in the United States. An extremely unusual case of an intramuscular infestation involving an extremity occurred in a 41-year-old man. Since the infestation closely resembled a soft-tissue tumor on clinical and roentgenographic examination, the patient was treated with an incisional biopsy of the mass, which consisted of a cystic cavity filled with clear fluid. The diagnosis of an Echinococcus cyst was made only after permanent section analysis revealed numerous scoleces within the cyst lining. The patient was asymptomatic six months after cyst excision but still remains at risk for recurrence of the infestation. The present report serves to alert the reader to this rare but potentially fatal condition. Preoperative diagnosis is imperative to avoid inadvertant rupture of a hydatid cyst, which releases viable scoleces into the systemic circulation and may precipitate an anaphylactic reaction.

A large amount of fluid extravasation into the surrounding muscle and soft tissue may occur during arthroscopy of the shoulder and particularly of the subacromial space. The tense swollen appearance of the shoulder has caused concern that the intramuscular deltoid pressure may become elevated to dangerous levels. Therefore, the intramuscular deltoid pressure was monitored in this study using a slit catheter. Although it was found that the intramuscular pressure became transiently elevated during the arthroscopic procedures, in every case the pressures promptly returned to normal levels within 30 min postoperatively. The clinical swelling and tenseness remained for a longer period. Despite a sometimes alarming amount of swelling during shoulder arthroscopy, intramuscular pressure elevations were only sustained for a short time and returned to normal levels very quickly after the cessation of fluid infusion.