Pediatric Sacroiliitis

  • Etiology:
    — Bilateral and symmetrical: Inflammatory bowel disease, ankylosing spondylitis, juvenile idiopathic arthritis
    — Unilateral: Neoplastic, infection
    — Pyogenic sacroiliitis is uncommon in kids accounting for 1-2% of cases of septic arthritis
  • Imaging Radiograph:
    — Poor sensitivity and specificity early on radiograph
    — Sclerosis of endplates especially on iliac side
    — Irregular joint end plates
    — Widened joint spaces
    — Erosions
  • Imaging MRI:
    — Marrow edema
    — Synovitis and capsulitis
    — Subchondral sclerosis
    — Erosions
    — Backfill
  • DDX: Mechanical stress, sacral insufficiency fracture
  • Complications:
  • Treatment: Treat underlying cause
  • Clinical:
    — Present with ipsilateral or bilateral buttock pain or lower lumbar spine pain
    — 50% can have pain radiating to lower extremity

Radiology Cases of Sacroiliitis

MRI of sacroiliitis
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.
MRI of sacroiliitis
Axial STIR MRI of the pelvis (above) shows increased signal in the right sacroiliiac joint on the sacral and iliac sides. Axial T1 MRI with contrast (below) shows increased enhancement of the right iliac bone and sacroiliiac joint.

Radiology Cases of Sacroiliitis in Psoriatic Arthritis

Radiograph of pediatric sacroiliitis
AP radiograph of the sacrum shows sclerosis and narrowing of the right sacroiliac joint. The left sacroiliac joint is normal.