Abstract
With the association between cardiovascular disease and urinary stone disease 1,2 and the vascular theory of Randall plaque formation, 3 there is a growing body of evidence to suggest that vascular calcification and kidney stone formation may share a common pathophysiology. 4 Sorting out this shared pathophysiology is a worthwhile endeavor as it could have significant implications in how urinary stone formers are counseled and treated. The authors are to be commended for their efforts to investigate a link between systemic biomineralization and urinary stone formation using calculated calcification scores and comparing these between kidney stone formers and nonstone formers. In their cohort of ∼400 patients, they found that kidney stone formers were more likely to have aortic and splenic artery calcifications than nonstone formers. They, therefore, concluded that patients with arterial calcifications may be at a higher risk of kidney stones.
The authors made an effort to match the kidney stone former and nonstone former groups based on age, gender, and body mass index, and they also controlled for tobacco history during their analysis. However, they chose kidney donor patients as the nonstone former cohort and this limits the generalizability of their findings. Kidney donors are typically healthier than the general population and thus likely to be overall healthier than the kidney stone former group in this study. This introduces a number of confounding comorbidities that make systemic calcifications more common in the kidney stone former group. Although the authors acknowledge this limitation, it should be noted that kidney stone formers had significantly more hypertension than the kidney donor group, and one major risk factor for vascular disease—diabetes mellitus—is not controlled for in their analysis. The authors mention that at least eight of the kidney stone formers had a known history of diabetes. As diabetic patients are excluded from kidney donation, this presents a limitation in using this cohort and opens the door for further study using a different set of matched patients to better address this confounding factor.
Stone composition is an additional element to this question that needs to be addressed. Uric acid stones and calcium-based stones are associated with various risk factors and comorbidities. Future studies would benefit from further analysis of various stone compositions and their association with vascular calcification scores.