Granulomatous renal masses following intravesical bacillus Calmette Guérin therapy: the central unaffected calyx sign.

A 67-year-old man with a history of melanoma, treated surgically 7 years before, was referred for vomiting and right flank pain after three intravesical instillations of bacillus Calmette-Guérin (BCG) for superficial bladder cancer. A CT scan showed a mass on the right kidney, with a normal calyx in its centre. Percutaneous biopsy, obtained because of melanoma history, showed granulomatous reaction caused by BCG infection. The renal mass disappeared after 9 months of anti-tuberculous treatment. The presence of an unaffected calyx in the centre of the renal mass is an interesting finding for both teaching purposes--it clearly illustrates the pathogeny of the disease, with the bacillus invading the renal parenchyma through the papilla--and diagnostic purposes--a malignant tumour is likely to displace or destroy neighbouring calyces rather than leaving them unaffected. However, the diagnostic value of this sign remains to be determined by further research.