Obturator Internus Muscle Abscess in Children

The authors describe four cases of obturator internus muscle (OIM) abscess in children, including their clinical presentations and treatment. This was a retrospective chart review. Children and adolescents younger than 18 years discharged between July 1, 1985, and September 30, 1998, from Brenner Children's Hospital with the diagnosis of muscle abscess or pelvic abscess were identified. A total of 56 patients were identified with the diagnosis of muscle abscess or pelvic abscess. OIM abscess was defined by radiologic findings of an inflammatory process with fluid collection in the OIM, along with the clinical findings suggestive of an OIM abscess. Four of the patients met the definition of OIM muscle abscess. The common presenting features were fever, limp, and hip pain. Computed tomography or magnetic resonance imaging was diagnostic in all four patients, and Staphylococcus aureus was the causative agent in each. All the patients recovered, one after surgical drainage and the other three after antimicrobial therapy alone or with needle aspiration. The presentation of OIM pyomyositis is similar to that of psoas muscle pyomyositis and other infectious processes of the pelvis and hip. The S. aureus is the most common etiologic agent but not the only one reported. Most patients can be managed without open surgical drainage, but needle aspirations may be helpful both therapeutically and diagnostically.