OBJECTIVE: To identify what risk factors on 24-hour urinalysis, if any, predispose patients to have higher percentages of uric acid (UA) stone composition in their stones, with specific emphasis on patients with pure UA stones.
METHODS: We retrospectively identified 308 patients from review of a kidney stone analysis database. Patients were grouped according to the percentage UA composition: 10%-20%, 30%-50%, 60%-90%, and 100% UA. Data were extracted from 24-hour urine collections and serum chemistries. Patients taking allopurinol, citrates, or thiazide diuretics were excluded.
RESULTS: The percentage UA stone composition increased as patients became older (P = .05) or heavier (P < .001). Gender did not impact the percentage of UA in stones. Although a higher serum UA level was associated with higher UA stone composition (P < .0006), urinary UA levels did not correlate (P = .1). In contrast, urinary pH correlated significantly with higher UA stone composition (P = .03).
CONCLUSION: Older and heavier patients with higher serum UA levels are more likely to have a pure UA stone. This information combined with traditional predictors (urine pH, radiopacity of stone, and Hounsfield units) may help identify those most likely to respond to dissolution therapy.
Written by:
Reichard C, Gill BC, Sarkissian C, De S, Monga M. Are you the author?
The Cleveland Clinic, Cleveland, OH.
Reference: Urology. 2015 Feb;85(2):296-8.
doi: 10.1016/j.urology.2014.10.029
PubMed Abstract
PMID: 25623669