Changes in Stone Composition over Two Decades: Evaluation of over 10,000 Stone Analyses

To examine the changes in stone composition from 1990 to 2010. A retrospective review was performed of all renal and ureteral stones submitted from the state of Massachusetts to a single laboratory (Laboratory for Stone Research, Newton, MA) for the years 1990 and 2010. Stone composition was determined by infrared spectroscopy and/or polarizing microscopy. A total of 11,099 stones were evaluated (56.7% from 1990, 43.3% from 2010). From 1990 to 2010, the percentage of stones from females (i.e., female/male ratio) increased significantly (29.8% in 1990 to 39.1% in 2010, p < 0.001). Among women, from 1990 to 2010, there was a significant increase in stones which were >50% uric acid (7.6-10.2%, p < 0.005) and a significant decrease in struvite stones (7.8-3.0%, p < 0.001). Among women with calcium stones, the % apatite per stone decreased significantly (20.0 vs. 11.7%, p < 0.001). Among men, there were no changes in stones which were majority uric acid (11.7-10.8%, p = 0.2). Among men with calcium stones, the % apatite per stone increased significantly (9.8 vs. 12.5%, p < 0.001). Males also demonstrated a significant increase in both cystine (0.1-0.6%, p < 0.001) and struvite stones (2.8-3.7%, p = 0.02). The epidemiology of stone disease continues to evolve and appears to vary according to gender. While some of these findings may be related to population changes in body mass index and obesity, the etiology of others remains unclear.