differential diagnosis for sacroiliitis

Magnetic

resonance images of sacroiliac joints: psoriatic arthritis. Shown are T1-weighted semi-coronal magnetic resonance images through the sacroiliac joints (a) before and (b) after intravenous contrast injection. Enhancement is seen at the right sacroiliac joint (arrow), indicating active sacroiliitis.

Wikipedia • CC BY 2.0

SAPHO

syndrome: the supposed trigger by isotretinoin, the efficacy of adalimumab and the specter of depressive disorder: a case report. MRI STIR images of lumbar osteitis and sacroiliac involvement before (upside) and after ADA treatment (downside)

ijponline.biomedcentral.com • CC-by-4.0

SAPHO

syndrome with pathological fractures of vertebral bodies: a case report. Axial MRI scans of the sacroiliac joints illustrated inflammatory bone changes at the right sacroiliac joint that were hypointense on the T1-weighted image (a) and hyperintense on the T2-weighted image (b)

bmcmusculoskeletdisord.biomedcentral.com • CC-by-4.0

Extrapulmonary

tuberculosıs: an old but resurgent problem. Pelvic x-ray of a 46-year-old male. The late finding of tuberculous sacroiliitis is characterized by degenerative changes in the left sacroiliac joint (arrows)

insightsimaging.springeropen.com • CC-by-4.0

Extrapulmonary

tuberculosıs: an old but resurgent problem. MR images of a 43-year-old male. Pre-contrast T1 weighted (a) and post-contrast (b) T1 weighted images demonstrate contrast enhancement in the synovium of the left sacroiliac joint in keeping with acute sacroiliitis (arrows). Arrowhead shows an abscess formation in the left iliac muscle that enhances peripherally after contrast injection

insightsimaging.springeropen.com • CC-by-4.0

Ankylosing

spondylitis • Sacroiliitis - grade III - Ganzer Fall bei Radiopaedia

Holland, M. Sacroiliitis - grade III. Case study, Radiopaedia.org. (accessed on 07 Nov 2022) https://doi.org/10.53347/rID-23359 • CC by-nc-sa 3.0 (modified)

Teenager with

low back pain. Axial (above left) and coronal (above right) STIR MRI without contrast of the sacroiliac joints shows a linear area of bright signal in the left iliac bone just lateral to the left sacroiliac joint. Axial (below left) and coronal (below right) T1 MRI with contrast shows enhancement in the same area.The diagnosis was left sacroiliitis.

pediatricimaging.org • CC-by-nc-sa 4.0

Radiopaedia • CC-by-nc-sa 3.0 • de

Sacroiliitis is an inflammation of one or both sacroiliac (SI) joints, and a common cause of buttocks or lower back pain. They can be a manifestation of a wide range of disease processes.

Clinical presentation

Symptoms of sacroiliitis can vary. People with sacroiliitis commonly present with ipsilateral or bilateral buttock and/or midline lower lumbar area pain. Up to 50% may have pain radiated to the lower extremity.

Pathology

The causes of sacroiliitis can be divided into unilateral or bilateral. See article: sacroiliitis (differential)

Radiographic features

Plain radiograph

Conventional radiography remains the first line of imaging despite its poor sensitivity and specificity in early disease. Specific sacroiliac joint views are helpful in the evaluation and comparing both sides of sacroiliac joints.

Radiograph findings include:

sclerosis of the endplates particularly on the iliac side
irregular joint end plates
widening of joint spaces

CT

CT examinations offer greater sensitivity, accuracy and detailed information compared to plain radiography. However, due to higher radiation exposure, it is not advisable to use CT for diagnosis or follow-up purposes.

Nuclear medicine

Bone scans demonstrate increased radioisotope activity of the joints and helpful in localizing the source of the pain. It is also valuable in excluding stress fractures and other bone pathologies.

MRI

Though not routinely used for evaluating the sacroiliac joints, MRI is capable of identifying early inflammatory changes of joints when other imaging is negative and excludes other differential causes such a disc prolapse which may resemble clinical symptoms of sacroiliitis.

MRI features of sacroiliitis can be divided into inflammatory and structural lesions :

inflammatory lesions

marrow edema (first to appear): high signal on water sensitive sequences
synovitis and capsulitis: thickening and contrast enhancement of the synovium and joint capsule
enthesitis: thickening and contrast enhancement of ligaments and tendons at their attachments to bone

structural lesions

subchondral sclerosis: bands of low signal (on all sequences) paralleling the joint margins, at least 5 mm from the joint space
erosions: marginal foci of articular bone loss
- low T1 signal
- high T2/STIR signal if active
- more prominent anteroinferiorly and on the iliac side of the SIJ
- when confluent may appear as joint space widening
periarticular fat deposition
ankylosis

Classifications

New York criteria (plain radiograph)
ASAS sacroiliitis classification system (MRI)

Treatment and prognosis

Treatment would depend on the cause of the disease. Physiotherapy may also be helpful in strengthening the pelvic muscle and increase the mobilization of the SI joint. Analgesics such as NSAIDs may be useful in symptomatic management. Surgical fusion of the SI joint is considered the last resort when other conservative management is ineffective.