Silicate nephrolithiasis after ingestion of supplements containing silica dioxide

Silicate calculi are common in some mammals, such as dogs and sheep, but extremely rare in humans. We report a case of silicate calculi in a woman using oral over-the-counter Uncaria tomentosa, Digestive Advantage and FlexProtex supplements. All 3 contained the excipient silica dioxide. Stone analysis showed composition of 100% silicate. The nephrolithiasis promptly abated after discontinuation of the products containing silica, then returned when the patient restarted her supplements. This case emphasizes the importance of stone analysis when obvious causes of nephrolithiasis are unclear and highlights the concerns of using over-the-counter supplements without substantial oversight.