Primary obturator externus pyomyositis in a child presenting as hip pain: a case report.

Hip pain in children often poses a diagnostic dilemma. Septic arthritis, Perthes disease, and slipped capital femoral epiphysis are among the most important causes. Pyomyositis involving muscles around the hip can present with similar features as septic arthritis and are difficult to diagnose because of their rarity and indolent presentation. Obturator internus and iliopsoas muscle abscess have been most commonly reported, with only 1 such report on isolated obturator externus muscle abscess. Routine laboratory investigations are nonspecific, and the diagnosis rests on imaging modalities. Magnetic resonance scan is the most useful investigation in the diagnosis and can pick up early changes in the muscle. Treatment involves appropriate antibiotic therapy with or without drainage. Most cases resolve completely. We report here a case of isolated obturator externus muscle abscess in an 11-year-old child illustrating the similarities with septic arthritis of hip and problems encountered during diagnosis and management.