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.

Gallstone detection at CT in vitro: effect of peak voltage setting.

This study was a retrospective single-institutional study approved by the Committee on Human Research and was HIPAA compliant. A waiver for informed consent was granted. The purpose of the study was to evaluate the effect of four peak voltage settings on the in vitro conspicuity of gallstones in an anthropomorphic phantom at computed tomography (CT). An anthropomorphic phantom was scanned with (n = 86) or without (n = 85) gallstones at CT by using 80, 100, 120, and 140 kVp. The sensitivity for gallstone detection was significantly higher at 140 kVp (86% [74 of 86] for reader 1 and 81% [70 of 86] for reader 2) than at lower voltage settings (up to 67% [58 of 86] for reader 1 and 63% [54 of 86] for reader 2, P < .05 for each reader), regardless of gallstone size (<1.0 cm vs > or =1.0 cm in diameter, P < .05 for each reader). CT attenuation measurements were not useful for determination of gallstone composition. Abdominal CT performed at 140 kVp may be useful when gallstone disease is of clinical concern.