Prevalence of hypertension and diabetes after exposure to extracorporeal shock-wave lithotripsy in patients with renal calculi: a retrospective non-randomized data analysis

This study shows two important results: First, patients with urolithiasis treated by shock waves at any location were at a higher risk to develop hypertension and diabetes during follow-up. Second, the odds to report hypertension or diabetes were not different in patients treated with shock waves for kidney stones compared to patients treated for distal ureter stones by SWL.

Regarding the first result, our multivariable regression analysis adjusted for known confounders confirmed that patients with urinary calculi are at a higher risk for long-term adverse effects including arterial hypertension [12‐14] and diabetes mellitus [15]. Therefore, studies observing potential long-term adverse effects of stone treatment should ideally compare patients with urinary calculi with or without treatment and not patients treated with urinary calculi compared to the general population. Otherwise, two conditions including the underlying metabolic dysfunction as well as the SWL treatment will be responsible for the higher prevalence of hypertension or diabetes.

Regarding the second result, patients after SWL to the kidney showed similar odds to report hypertension or diabetes compared to patients after SWL to the distal ureter. Patients who had shock waves to the distal ureter were chosen as the main comparison group within SWL treated patients, as the distal ureter is as most far afield to the kidneys and pancreas and thus both organs were not exposed to shock waves in the distal ureter group. Taken together, our data do not support the hypothesis that SWL to the kidneys leads to a higher odds to report hypertension or diabetes after long-term follow-up. Our present findings are in line with our recent systematic review, in which the evidence for SWL causing hypertension or diabetes was weak [8].

Since our review in 2013, two further systematic reviews including the same studies [16, 17] and two cohort studies have been published. The first systematic review looked at new-onset diabetes after SWL for urinary stones and concluded that there is no association between SWL and new-onset diabetes [16]. The second review focused on long-term renal functions after SWL in the pediatric population and concluded that there is no evidence suggesting long-term damage [17]. The first cohort study by Pirola included 100 patients treated by SWL and found that creatinine values remained unchanged and the prevalence of diabetes and hypertension seems to be similar to the general population [18]. However, this study compared a SWL cohort of kidney stone patients with the general population. This limits its interpretation as patients with urolithiasis are in general at a higher risk to develop hypertension and diabetes during follow-up as discussed above. The second retrospective study by Denburg et al. [19] included 1319 patients treated by SWL with a follow-up of less than 4 years. They found that SWL was associated with a significant increased risk of hypertension. When they further stratified if SWL was applied to the kidney or ureter, only SWL to the kidney was significantly and independently associated with hypertension.

The result of our study and that of von Denburg have to be interpreted in the context of the study design. A major confounding variable may represent stone burden differences in the kidney and ureter group. In both studies, it was not possible to account for number and size of kidney stones. Therefore, patients with more and/or larger stones due to worse metabolic disease are more likely to be in the kidney stone group, which represent a possible confounder. We found that patients with an increasing number of shock waves (per 1000 shock waves) to the kidney were more likely to report hypertension or diabetes at follow-up. The observed dose dependence raises the question whether this association is causal. However, recurring treatment is more likely needed in patients with underlying metabolic dysfunction causing recurrent stone formation which again might be an important confounder.

Limitations of our study are the moderate questionnaire response rate and the unavailable information regarding hypertension or diabetes at time-point of SWL. Additionally, currently used lithotripter, newer settings (e.g., ramping [20, 21]) and co-current medications [22] have been discussed to reduce damage to the kidneys but were not used in this study. Nevertheless, in the absence of prospective data from larger cohorts with an appropriate follow-up, our study is a unique and valuable opportunity to study long-term adverse effects. Furthermore, our medical chart review minimizes the misclassification bias as no automatic code extraction was used.