Brucellosis is a worldwide zoonosis. Consumption of unpasteurized milk and occasional animal contact were found to be the source of infection in the general population.
Patients present typically with fever, which can be undulating and last for 2-3 weeks. Arthralgia, myalgia and back pain are also common.
Blood tests will be done to diagnose the infection and determine the type of Brucella.
Brucellosis may affect any body part and may be focal or systemic, but it has an affinity for infecting the lumbar spine. Spondylodiscitis is the commonest complication of brucellosis and its reported incidence is 6% to 58%. Sacroilitis due to brucellosis is usually unilateral [1, 2].
Conventional x-ray is usually the initial imaging method used for the diagnosis of sacroilitis. However, it has low sensitivity for detecting bone abnormalities in the early stages of the disease.
Computed Tomography shows higher sensitivity for detecting minimal bone erosions and joint space narrowing.
MRI has been suggested as the method of choice in the evaluation of sacroiliitis, because of absence of ionizing radiation, its capacity of demonstrating early alterations and inflammatory activity of the disease. Coronal and axial images should be obtained, usually in the oblique plane .
-Erosions are bone defects at the joint margins and reflect structural damage due to inflammation.
-Subchondral bone marrow edema characterized by low-intensity signal on T1- and high-intensity signal on T2-, especially T2-weighted fat-supressed and STIR sequences. On T1-weighted fat-supressed sequences, after intravenous gadolinium injection, enhancement in sacroiliac joint space and surrounding bone marrow can be observed, and this finding is highly suggestive of an active disease.
-Interarticular fluid collection is better seen on T2-, mainly on T2-weighted fat-supressed and STIR sequences [3, 4].
-Periarticular muscle edema usually in the iliopsoas muscle, is strongly indicative of infectious sacroiliitis. Therefore, the surrounding muscles should be thoroughly examined for abnormal signal intensity when evaluating the sacroiliac joints .
Patients of brucella spondylitis and sacroliitis are treated with a combination of antibiotics for a minimum of 6-8 weeks up to 6 months, depending on the severity of the disease .
In conclusion, MRI is the most important imaging modality in early diagnosis of infectious sacroiliitis. It is particularly helpful in demonstrating early alterations, activity of the disease and response to treatment. Awareness of MRI findings of brucella-related sacroiliitis in different stages is essential for diagnosis and treatment of this condition.