Metabolic syndrome and urinary stone composition: what factors matter most?
OBJECTIVE
To determine which metabolic syndrome (MetS) factors lead to differences in stone composition in a multivariate analysis.


METHODS
We retrospectively reviewed medical charts of patients who had a kidney stone removed over a 5-year period (2006-2011). MetS factors (obesity [body mass index {BMI} >30], diabetes mellitus [DM], hypertension [HTN], and dyslipidemia [DLD]) were tallied in each patient. For the latter 3 factors, medical treatment for the condition was used to tag a patient with the condition. Stone composition was determined by the dominant (>50%) component. Statistical analysis was designed to determine which MetS factors were independently associated with differences in stone composition.


RESULTS
Five hundred ninety kidney stones were included in the analysis. Patients with MetS had a higher prevalence of uric acid stones and lower prevalence of calcium phosphate stones. HTN and DM were independently associated with differences in composition, specifically uric acid stones (higher proportion), and calcium phosphate stones (lower proportion). Obesity was not associated with differences in composition, although a secondary analysis of morbidly obese patients showed a higher proportion of uric acid stones and a lower proportion of calcium oxalate stones.


CONCLUSIONS
HTN and DM are the MetS factors independently associated with differences in stone composition, specifically the uric acid and calcium phosphate components. Obesity has little effect on stone composition until a very high (>40) BMI is reached. The overall effect of MetS factors on stone type is relatively small, because most stones are calcium oxalate and MetS factors have little impact on calcium oxalate frequency.
Loyola University Medical Center, Department of Urology, Fahey Center, Maywood, IL 60153, USA. akadlec@lumc.edu
Adam O
AO
Kadlec
Kristin
K
Greco
Zachary C
ZC
Fridirici
Spencer T
ST
Hart
Ted
T
Vellos
Thomas M
TM
Turk
D000328:Adult; D000368:Aged; D002129:Calcium Oxalate / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis*; D048909:Diabetes Complications / Q000150:complications / Q000378:metabolism; D050171:Dyslipidemias / Q000150:complications / Q000378:metabolism; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000378:metabolism; D007669:Kidney Calculi / Q000737:chemistry* / Q000150:complications; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications / Q000378:metabolism*; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000150:complications / Q000378:metabolism; D012189:Retrospective Studies; D014527:Uric Acid / Q000032:analysis*
D002130:Calcium Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; C020243:calcium phosphate