Kidney stones and kidney function loss: a cohort studyBMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e5287 (Published 30 August 2012) Cite this as: BMJ 2012;345:e5287
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Does lithotripsy contribute to adverse renal outcomes associated with renal stones?
Davor Eterović, Ph.D., Professor, Department of Nuclear Medicine, University Hospital Split and Department of Medical Physics, University of Split Medical Faculty
Marijan Šitum, M.D., Ph.D., Department of Urology, University Hospital Split and University of Split Medical Faculty
Vinko Marković, M.D., Ph.D., Department of Nuclear Medicine, University Hospital Split and University of Split Medical Faculty
Ante Punda, M.D., Ph.D., Department of Nuclear Medicine, University Hospital Split and University of Split Medical Faculty
In the large population-based cohort study Alexander et al. have shown that occurrence of kidney stones is linked with substantially increased risk of adverse renal outcomes, especially in women and in younger people.1 They interpreted this association as a causal one, suggesting calcification caused progressive renal scarring as a mechanism.
Large proportion of symptomatic renal stones is currently treated with the shock-wave lithotripsy (SWL). On the other hand, SWL induced renal injury has been linked with arterial hypertension.2 Chronic arterial hypertension may, in turn, contribute to development of chronic kidney disease. Thus, the adverse effects of SWL may have contributed to the observed excess incidence of adverse renal outcomes.
However, the recent reports have failed to validate the association of SWL and hypertension or diabetes mellitus.2 We offer an explanation for this apparent inconsistency. The cohort studies in question defined the adverse effect of SWL as the new onset hypertension. In this way one ignores the possibility that relief of renal obstruction lowers the blood pressure. If so, the observed increased or unchanged blood pressure following SWL reflects the oscillations around the balance between renal injury (increasing blood pressure) and relief of obstruction (decreasing blood pressure).
We have already presented a body of evidence that shock-wave lithotripsy (SWL) induces chronic injury to treated kidney in virtually all patients, leading to chronic deterioration of kidney internal and control functions, including blood pressure and possibly erythropoiesis.3-5 Most notably, at baseline our SWL patients had roughly doubled vascular resistance of the affected kidney. This by itself is enough to cause some 5 mm Hg raise in the arterial blood pressure, in comparison with pre-obstructive state. Despite relief of obstruction, the increased renal vascular resistance persisted at 3 months following SWL.4 In this situation it is very likely that the unchanged blood pressure following SWL represents a balance between the effects of renal vascular injury and cessation of hemodynamic impacts of renal obstruction.
Anyhow, since relatively small change in arterial blood pressure is associated with substantial change in the risk of arterial vascular events,6 looking for the new onset hypertension is insensitive measure of SWL related adverse effects. Thus, the current evidence speaks for SWL related adverse effect on control of blood pressure, which may contribute to increased risk of adverse renal outcomes in people with renal stones.
1 Alexander TR, Hemmelgarn BR, Wiebe N, et al. Kidney stones and kidney function loss: a cohort study. BMJ 2012;345:e5287.
2 Pearle MS. Shock wave lithotripsy for renal calculi. N Engl J Med 2012;367:50-7.
3 Eterović D, Šitum M, Juretić-Kuščić Lj, Dujić Ž. A decrease in blood pressure following pyelolithotomy but not extracorporeal lithotripsy. Urol Res 2005;33:93-8.
4 Eterović D, Juretić-Kuščić Lj, Čapkun V, Dujić Ž. Pyelolithotomy improves while extracorporeal lithotripsy impairs kidney function. J Urol 1999;161:39-44.
5 Eterović D, Šitum M, Punda A, Marković V, Kokić S. Urinary obstruction depresses erythropoiesis which recovers after parenchyma-saving surgery but not SWL. Urol Res 2010;38:51-6.
6 Verdecchia P, Gentile G, Angeli F, Mazzotta G, Mancia G, Reboldi G. Influence of blood pressure reduction on composite cardiovascular endpoints in clinical trials. J Hypertens 2010;28:1356-65.
Competing interests: No competing interests