Table I. Patient demographics.

	Stone formers	Controls
Number:
Total	57	57
Male	38	51
Female	19	6
Mean age	54.9	52
Stone burden:
Single stone	24
Multiple stones	33
Non-malignant urological problem:
Simple penile/scrotal surgery		29
TURPa/optical urethrotomy/urethral dilatation		18
Other		10

^a TURP, transurethral resection of prostate.