Related Experiment Video
Updated: Jun 23, 2025

Estimation of Urinary Nanocrystals in Humans using Calcium Fluorophore Labeling and Nanoparticle Tracking Analysis
Published on: February 9, 2021
Case of drug-induced kidney stone from overuse of phenazopyridine
Suraj Pursnani1, Necole M Streeper1
1Department of Urology, Penn State Health Milton S. Hershey Medical Center, Hershey, Pennsylvania, USA.
Abstract:
Drug-induced nephrolithiasis represents only 1%-2% of stone cases. Here we focus on drugs capable of crystallizing and forming stone, specifically phenazopyridine (Pyridium/Azo). This is a case of a patient who presented with a stone conglomerate in the right proximal ureter and underwent definitive treatment. Interestingly, the stone had a purple hue with FTIR spectroscopy showing stone composition of calcium oxalate (monohydrate and dihydrate) and a material resembling phenazopyridine. We retrospectively learned that she used multiple extended courses of phenazopyridine over 3 months.
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