Abstract
Objective: The study was designed to determine the frequency and patterns of bone metastases in renal and urinary bladder carcinomas on skeletal scintigraphy.

Methods: This retrospective cross sectional study included 76 sequential patients with renal and urinary bladder carcinomas referred for a 99mTc-MDP whole-body bone scan to the Nuclear Medical Centre, AFIP Rawalpindi, from Jan 2011 to Jan 2013. Focal increased radiotracer uptake seen on the bone scans was identified as an osteoblastic or 'hot' lesion, whereas a photon-deficient area was labelled as an osteolytic or 'cold' lesion.

Results Out of 76 patients, renal cell carcinoma was the commonest at 64%, followed by urothelial carcinoma at 27%, transitional cell carcinoma at 5% and clear-cell carcinoma 4%. Three-fourths (75%) of the patients were male and a quarter (25%) female with a mean age of 60 years. 52.6% were negative for skeletal metastases and 47.4% positive. Commonly involved sites in decreasing frequency included the lumbar vertebrae (61%), dorsal vertebrae (25%), the ribs (25%), pelvic bones (22%), sternum (5%), proximal femoral and humeral halves (5%), scapula (2%) and skull (2%). Lytic lesions were present in 11% of the cases.

Conclusion: Skeletal metastases were found in 47.4% of the cases of renal/urinary bladder carcinomas with the lumbar spine being the commonest site involved. In addition to typical 'hot' osteoblastic lesions, 'cold' osteolytic lesions were also present in a small with significant number of cases, which appear deceptive and warrant a meticulous survey of bone scan images in patients with renal and bladder cancers.