Acute bacterial sacroiliitis in an adult: a case report and review of the literature.

Bacterial septic sacroiliitis is an uncommon diagnosis that occurs most frequently in children and young adults. Nonspecific physical examination findings often make it difficult to diagnose the condition, thus delaying appropriate treatment. We review the case of middle-aged woman with sacroiliac joint (SIJ) pain after a torsional injury. Radiographic films showed the pelvis and left lower extremity to be normal. Despite anti-inflammatory medications, analgesics, a corticosteroid injection, and physical therapy, her pain persisted. Laboratory data showed an elevated erythrocyte sedimentation rate and C-reactive protein; otherwise, tests were normal, including negative blood cultures. Magnetic resonance imaging (MRI) revealed a left posteroinferior SIJ effusion and computed tomography (CT) showed an effusion and irregularity in the left SIJ. An SIJ biopsy revealed inflammation suggestive of osteomyelitis. After a course of intravenous antibiotics, the symptoms completely resolved, thus supporting our diagnosis of bacterial sacroiliitis. Repeat MRI and CT confirmed the complete resolution of the sacroiliitis.