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WCET 2022: Urinary Citrate and pH Are Not Correlated in Calcium Stone Formers, Only in Uric Acid Stone Formers

(UroToday.com) On the third day of the 39th World Congress of Endourology and Uro-Technology, a session was dedicated to clinical stones and medical management. The moderators for this session were Dr. Kevin Koo from Mayo Clinic and Dr. Arun Rai from Hofstra University. They discussed multiple clinical and non-clinical approaches for stone management which included a novel presentation from a clinical fellow of endourology at the University of California, San Francisco, Dr. Wilson Sui. Dr. Sui presented a study focusing on the correlation between 24-hour urinary citrate and pH in patients with nephrolithiasis and specific stone former patients.

One of the commonly used methods to manage stone episodes and recurrence rate is alkalization of urine with citrate therapy. Previously conducted research has shown that citrate therapy in uric acid stone former patients have been effective which reduced the urine pH and reoccurrence rate. However, the efficacy and outcome of citrate therapy in calcium stone former patient is still under review. Dr. Wilson Sui and colleagues investigated the urine citrate increase and the urinary pH increase in all patients with nephrolithiasis and measured whether the change was significant only in specific stone-former patients.

Patients who had conducted 24 hours urine analysis were recruited for the study. Patients with donor nephrectomy were recruited as a control group study. Demographic information and 24-hour urine results were recorded in the study analysis. Non-parametric tests such as Mann-Whitney tests and Spearman correlations were applied.

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A total of 450 patients were included in this study. The control group had a significant citrate increase and was younger than the experimental group with no significant difference in BMI and urine pH. The median 24-hour urine citrate, pH voided volume was 544.3 mg/kg/24hr, 6.2, and 2.1L, respectively. Based on Figure 1, a positive correlation was identified between the 24-urine citrate and urine pH in the stone former group with R = 0.096 and p = 0.04; However, no correlation was identified in the control donor nephrectomy group with R = 0.036 and p = 0.61. Subsequently, the stone former group was sub-stratified with respect to composition, which indicated a significant correlation between urine citrate and urine pH in uric acid stone formers but not in calcium stone formers. The stone composition category and pH correlation were demonstrated in figure 2.

Based on the obtained results of the study, it was evident that citrate therapy significantly increased the urinary pH, and reduced the recurrence rate in uric acid stone formers but not calcium stone former patients. Therefore, a conclusion was made that 24-hour urinary citrate and 24-hour pH are significantly correlated in Uric acid stone formers but no other stone former groups. Further investigation for therapeutic treatment plans for non-uric acid stone former is needed.

Presented by: Wilson Sui, MD from the University of California San Francisco

Written by: Val Saadat, B.S, Junior Specialist Researcher, Department of Urology, University of California Irvine, @Val_Saadat on Twitter during the 39th World Congress of Endo urology and Uro-Technology (WCET), Oct 1 - 4, 2022, San Diego, California. 

References:

  1. Pearle, M.S., et al., Medical management of kidney stones: AUA guideline. J Urol, 2014. 192(2): p. 316-24.
  2. Turk, C., et al., EAU Guidelines on Diagnosis and Conservative Management of Urolithiasis. Eur Urol, 2016. 69(3): p. 468-
  3. Pak, C.Y., K. Sakhaee, and C. Fuller, Successful management of uric acid nephrolithiasis with potassium citrate. Kidney Int, 1986. 30(3): p. 422-8.