Login to Access Video or Poster Abstract: MP01-20
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Introduction

Urolithiasis is a global health problem with a lifetime risk of up to 15 % in white men and 6 % in women and a recurrence rate of about 50 % in these patients. Over the last three decades (and since the introduction of shock wave lithotripsy [SWL]) there was a change in stone composition observable with an increasing prevalence of calcium phosphate stones. Calcium phosphate crystallization is driven by urinary calcium phosphate supersaturation which rises with elevated urine pH. A recent animal study revealed an increase in urine pH of SWL treated porcine kidneys. We therefore evaluated the effect of SWL on urine pH in the Swiss Kidney Stone Cohort (SKSC), a nationwide, multicenter, prospective register of kidney stone patients.

Methods

Of the first 350 patients enrolled in the SKSC register, 170 patients were eligible; 180 patients had to be excluded because of a short follow-up of <6 months, uric acid stone composition and/or incomplete data on previous stone treatment. The patients were grouped into 3 different groups according to their previous treatment: group A: SWL (n=49), group B: endourological treatment (n=67), group C: spontaneous stone passage (control group; n=54). The paired t-test and one-way ANOVA was used to compare the change of urine pH over time within and between the 3 different groups.

Results

44/170 (26%) patients were female. Median patient age was 47 years (range: 20-86). Stone composition was available in 57% of patients and did not significantly differ between the three groups (p=0.8). The median urine pH at first visit (≥ 4 weeks post stone passage or intervention) was slightly higher in group A after SWL as compared to the other two groups: pH 5.7 (IQR: 5.1-6.0) in group A; pH 5.5 (IQR: 5.0 -5.9) in group B; pH 5.5 (IQR: 5.1-6.0) in group C; p=0.4. There was a significant rise in urine pH at follow-up visit (3-6 months after initial visit) in group A after SWL treatment whereas no significant change was seen in the non-SWL groups B and C (median pH difference in groups A, B and C: +0.25, -0.19 and -0.005, respectively; p<0.001).

Conclusions

There was an increase in urine pH in patients who had undergone SWL while this was not seen in urinary stone patients who were treated endourologically or conservatively. This suggests that SWL may cause tubule cell injury that leads to functional disturbances such as changes of urine pH. Whether this has an impact on the rate of recurrences or future stone composition (increase in calcium phosphate content) will be explored in the further follow-up of these patients.

Funding

none