On bone scintigraphy with 99mTc-MDP, a 'superscan' shows diffusely increased skeletal uptake with absent renal activity and suppression of soft tissue background. This pattern is MOST commonly caused by:

• A Paget's disease with monostotic involvement
• B Renal osteodystrophy with normal bony architecture
• C Fractures with reactive bone formation
• D Widespread osteoblastic metastases (prostate or breast carcinoma) ✓

Explanation

A 'superscan' on bone scintigraphy describes diffusely increased tracer uptake throughout the skeleton with absent or markedly reduced kidney visualization (due to near-complete extraction of tracer by bone) and suppressed soft tissue background. The most common cause is diffuse osteoblastic metastases, particularly from carcinoma prostate (dense sclerotic metastases) and breast cancer. Other causes include severe metabolic bone disease (renal osteodystrophy, hyperparathyroidism, osteomalacia) and Paget's disease (usually polyostotic). The uniformity and pattern differ: metastatic superscan is heterogeneously intense, while metabolic superscan shows uniform involvement with 'tie' sign in sternum and 'tram lines' in long bones.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.