Can 24-hour urine stone risk profiles predict urinary stone composition?
OBJECTIVE
Distinguishing calcium oxalate from uric acid stones is critical to identify those patients who may benefit from dissolution therapy and can also help direct preventive measures for stone growth. We aim to study whether 24-hour urine analysis may predict the urinary stone composition.


METHODS
We retrospectively identified patients with calcium oxalate and uric acid stone compositions who also had a 24-hour urine collection within 3 months of stone analysis. Patients with calcium phosphate, cystine, and other stone compositions were excluded. Subjects were divided based on their stone type (calcium oxalate vs uric acid stones) and were compared according to demographic data and 24-hour urine analysis. Logistic regression analysis was performed to assess the association between stone composition and covariates. A nomogram was then constructed to predict uric acid stones over calcium oxalate stones.


RESULTS
Of the 1163 patients identified, 1054 (90.6%) had calcium oxalate stones and 109 (9.4%) had uric acid stones. On logistic regression, body mass index (BMI) (odds ratio [OR] 1.351, 95% confidence interval [CI] 1.133-1.609; P<0.001), urinary sodium (OR 1.021, 95% CI 1.004-1.037; P=0.013), calcium (OR 0.987, 95% CI 0.979-0.996; P=0.003), oxalate (OR 0.890, 95% CI 0.804-0.985; P=0.024), and uric acid (OR 0.989, 95% CI 0.982-0.997; P=0.005) were significant predictors for urinary stone composition. The nomogram with the highest concordance index (c-index=0.855) was obtained using age, BMI, urinary sodium, calcium, oxalate, and uric acid as variables.


CONCLUSIONS
Distinguishing uric acid from calcium oxalate stones can be performed with relative accuracy using parameters from the 24-hour urine stone risk profile and the patient's BMI and age.
Stevan B. Streem Center for Endourology & Stone Disease, Glickman Urological & Kidney Institute , The Cleveland Clinic, Cleveland, Ohio.
Fabio C M
FC
Torricelli
Shubha
S
De
Xiaobo
X
Liu
Juan
J
Calle
Surafel
S
Gebreselassie
Manoj
M
Monga
D015992:Body Mass Index; D002118:Calcium / Q000652:urine; D002129:Calcium Oxalate; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000652:urine; D008297:Male; D008875:Middle Aged; D053040:Nephrolithiasis / Q000652:urine; D049451:Nomograms; D010070:Oxalates / Q000652:urine; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012189:Retrospective Studies; D012964:Sodium / Q000652:urine; D013997:Time Factors; D014527:Uric Acid
D010070:Oxalates; D002129:Calcium Oxalate; D014527:Uric Acid; D012964:Sodium; D002118:Calcium