Identification of melamine/cyanuric acid-containing nephrolithiasis by infrared spectroscopy

Melamine-contaminated milk formula caused infant nephrolithiasis in some areas of China. Its combination with cyanuric acid causes crystallization in renal tubules. Following this renal damage and even renal failure that require long-term hemodialysis has been reported. Therefore, correct and timely diagnosis of these complex diseases is critical. Melamine containing stone is a combination of equal molar ratios of common stone compositions that has been reported from previous animal studies. We have previously identified the compositions of urinary tract stones with infrared (IR) spectroscopy. We hypothesized that the absorbance of wavelength of IR can identify melamine/cyanuric acid in the presence of mixing human stone compositions. In this study, we made an artificial stone composition and examine under IR absorbance by mixing equal molar ratios of melamine/cyanuric acid with different types of human urinary stones, and established a reference of IR analysis for the identification of melamine/cyanuric acid-containing human urinary tract stones. Knowledge of the precise stone composition allowed institution of appropriate prophylactic dietary and medical therapy and this may help in the prevention of urinary stone recurrence. The results are promising that melamine and cyanuric acid can be identified clearly in a low percentile (∼1%) of stone mixture pellet. Therefore, IR seems to be an ideal tool for the identification of melamine/cyanuric acid-containing stones.