107 Unilateral Sacroiliitis (with Osteomyelitis) and Adjacent Cellulitis

Clinical Presentation

A 36-year-old man with a history of intravenous drug abuse presents with right hip and flank pain radiating down his right leg.

Fig. 107.1 Whole-body planar image, anterior and posterior projections, ⁶⁷Ga.

Technique

• A 7.5 mCi dose of ⁶⁷Ga-citrate is injected intravenously 3 days before scan.

• Whole-body imaging in anterior and posterior projections

Dual-detector gamma camera

Medium-energy collimators

Energy peak at 93-, 185-, and 300-keV photopeaks

Image Interpretation

Intense tracer uptake is noted in the region of the right sacroiliac joint (Fig. 107.1). Note the “cold” center on the posterior view; this suggests an advanced process with central devitalization (necrosis). Faint tracer uptake is apparent in the soft tissues of the right buttock.

Differential Diagnosis

• Osteomyelitis

• Sacroiliitis

• Soft tissue inflammation/infection

• Acute trauma

• Malignancy

Diagnosis and Clinical Follow-Up

Findings consistent with unilateral sacroiliitis (with osteomyelitis) and adjacent cellulitis. Correlative MRI demonstrates local sacroiliac bone destruction and edema of adjacent gluteus muscles.