Table 3.

 Characteristics of patients with or without preoperative renal stone episodes. Values are means (SD)

Variable	Patients with stones (n=167)	Patients without stones (n=506)	P value
Age (years)	53.0 (15.5)	59.8 (14.5)	<0.01*
Weight of diseased tissue (g)	1.95 (3.99)	2.36 (5.72)	0.42*
Median (range)	1.19 (0.02-40)	1.01 (0.03-87)
No (%) of patients with adenoma	457 (90)	148 (89)	0.53†
No (%) of patients with hyperplasia	49 (10)	19 (11)
Serum ionised calcium (mmol/l)§	1.57 (0.14)	1.58 (0.17)	0.72*
Male:female ratio	35:65	23:77	<0.01†
No (%) of patients with osteoporosis before diagnosis	1 (1)	14 (3)	0.13‡
No (%) of patients with osteoporosis after diagnosis	0	7 (1)	0.20‡
No (%) of patients with fracture before diagnosis	17 (10)	57 (11)	0.70†
No (%) of patients with fracture after diagnosis	11 (7)	47 (9)	0.28†

Data on stones before operation were missing in one patient. 

^*Independent samples t test (two sided). 

^†χ² test. 

^‡Fisher's exact test (two sided). 

^§Measured on the day before surgery.