The role of CT in the diagnosis of sacro-iliitis

Ankylosing spondylitis is a progressive, debilitating disease in which early diagnosis and early treatment can improve the prognosis. Radiographic confirmation is essential for diagnosis but conventional radiography has not proved useful, particularly in the early course of the disease. The aims of this study were to correlate the findings at conventional radiography with those at CT, and to correlate the duration of clinical symptoms with the radiological findings.

Forty patients with clinical sacro-iliitis and 13 controls were evaluated by means of conventional radiography and CT.

Conventional radiography was positive in 10/40 patients and CT in 30/40 patients. Conventional radiography was positive in only 2/14 patients with a symptom duration of less than 2 years while CT was positive in 10/14 such patients.

The study demonstrated a considerably higher sensitivity in CT than in conventional radiography in detecting the subtle changes necessary for the radiological diagnosis of sacro-iliitis, particularly in cases of short duration. CT allows an early start to be made in treatment with a consequently improved prognosis. The use of conventional radiography cannot be recommended because its low sensitivity delays diagnosis in many instances.