Septic sacroiliitis in children.

We retrospectively reviewed the clinical, laboratory, and magnetic resonance (MR) imaging features of 8 patients with septic sacroiliitis. The age of the patients ranged from 4.3 to 15.2 years. None of the patients were accurately diagnosed before presentation. Misdiagnosis was largely caused by the wide variety of clinical symptoms including hip, back, knee, and abdominal pain, by low suspicion of the disease, and by negative radiographic findings. Magnetic resonance examination was performed in all patients and confirmed the diagnosis. All patients were treated with bed rest and intravenous antibiotics. Clinical and laboratory findings improved in all patients during antibiotic treatment, but MR findings showed a mixed response with resolution of effusions in the sacroiliac joint, muscular infiltration, and abscess formation, but progressive changes in signal intensity in the adjacent bone marrow of the sacrum and ilium. After treatment, the signal changes in the bone marrow persisted for 2 to 3 months.