Computed tomography in diagnosis of septic sacroiliitis: report of three cases.

Disorders of the sacroiliac joint are often overlooked during an initial physical examination because the patient is usually in a supine position and the posteriorly located joint is not accessible. Local pain and tenderness at the sacroiliac joint on lateral compression of the pelvis, together with Gaenslen and Fabere maneuvers, may direct the physician's attention to the joint. However, these symptoms are not specific or pathognomonic. Unusual presentation of septic sacroiliitis, which does not show radiologic changes during the early stages, may mimic gluteal, lumbar disc or intra-abdominal syndromes, leading to unnecessary abdominal exploration or lumbar discectomy. Computed tomography (CT), with its superb delineation of osseous, synovial and peri-articular structures, was applied to diagnose septic sacroiliitis in three patients. In Patient 1, septic arthritis and juxta-articular osteomyelitis with sequestrum formation were demonstrated by CT four weeks before abnormalities were shown on a roentgenogram. In Patients 2 and 3, inflammatory processes affected the synovium and peri-articular muscles; thus, abnormalities were shown by CT but not by a roentgenogram. We consider CT to be helpful and superior to conventional radiography in the diagnosis of septic sacroiliitis.