Obturator internus pyomyositis presenting as a pararectal abscess.

This report describes two children who presented with fever, hip pain and a limp, and were subsequently found to have a primary pyomyositis of the obturator internus muscle. A clinical diagnosis of septic arthritis of the hip was made initially, but in both children MRI showed a pararectal abscess, which required incision and drainage. Staphylococcus aureus was cultured from pus from the abscesses and both children made a full recovery subsequently. This report highlights the main features of this unusual entity and emphasises the need for early imaging in the child with an unexplained limp.