Stone Composition as a Function of Age and Sex

Abstract

Background and objectives Kidney stones are heterogeneous but often grouped together. The potential effects of patient demographics and calendar month (season) on stone composition are not widely appreciated.Design, setting, participants, & measurements The first stone submitted by patients for analysis to the Mayo Clinic Metals Laboratory during 2010 was studied (n=43,545). Stones were classified in the following order: any struvite, any cystine, any uric acid, any brushite, majority ($50%) calcium oxalate, or majority ($50%) hydroxyapatite.Results Calcium oxalate (67%) was the most common followed by hydroxyapatite (16%), uric acid (8%), struvite (3%), brushite (0.9%), and cystine (0.35%). Men accounted for more stone submissions (58%) than women. However, women submitted more stones than men between the ages of 10-19 (63%) and 20-29 (62%) years. Women submitted the majority of hydroxyapatite (65%) and struvite (65%) stones, whereas men submitted the majority of calcium oxalate (64%) and uric acid (72%) stones (P,0.001). Although calcium oxalate stones were the most common type of stone overall, hydroxyapatite stones were the second most common before age 55 years, whereas uric acid stones were the second most common after age 55 years. More calcium oxalate and uric acid stones were submitted in the summer months (July and August; P,0.001), whereas the season did not influence other stone types.Conclusions It is well known that calcium oxalate stones are the most common stone type. However, age and sex have a marked influence on the type of stone formed. The higher number of stones submitted by women compared with men between the ages of 10 and 29 years old and the change in composition among the elderly favoring uric acid have not been widely appreciated. These data also suggest increases in stone risk during the summer, although this is restricted to calcium oxalate and uric acid stones.

Relative Supersaturation of 24-Hour Urine and Likelihood of Kidney Stones

“…7 For this present study, we do not have stone composition reports for most participants, though it is expected that the majority of stones were CaOx. 8–11 Although it is likely that less than 10% of stones were 100% UA 10,11 , we analyzed UA supersaturation for this study for completeness, but given the low percentage, these results should be interpreted with caution.…”

Urinary Stone Disease: Advancing Knowledge, Patient Care, and Population Health

“…Stone composition may also vary by age and sex. Women have fewer calcium oxalate monohydrate stones and more struvite and calcium phosphate stones (23,26). Uric acid stones are more likely in men and the elderly (26).…”

“…Women have fewer calcium oxalate monohydrate stones and more struvite and calcium phosphate stones (23,26). Uric acid stones are more likely in men and the elderly (26). Additional research on USD risk also is needed to explore hormonal effects, such as estrogen and progestin influences on urine chemistry, particularly given increasing USD frequency among adolescent girls and adult women (1,2,24).…”

Probiotics for prevention of urinary stones

“…Thus, perhaps it is not surprising that 70% or more of kidney stones are composed of CaOx (1). Given that the urine of most persons is supersaturated for CaOx, one might indeed wonder why everyone does not form stones.…”