Analysis of children's kidney stones and comparison to canine kidney stones: Both resulting from ingesting adulterated food products.

Kidney stones resulting from ingestion of melamine-tainted food products were originally detected in dogs and cats in 2004 and 2007. Nephroliths were removed at necropsy from dogs that had died from acute kidney injury in Asia in 2004. Samples of these were submitted to our laboratories for analysis. The presence of a mixed s-triazine matrix comprising melamine, cyanuric acid, and ammelide, but no detectable ammeline was found in the canine stone samples we analyzed. The unusual and unique green coloration of these stones was attributed to the presence of biliverdin. The techniques developed in the canine study were applied to the analysis of human kidney stones. In 2008, high levels of melamine were detected in some infant formula and other liquid and powdered milk products originating from China. Human kidney stones, resulting from this type of contamination, were obtained from children, and analyzed using mass spectral techniques. The results indicated the presence of melamine, ammeline, uric acid, but no ammelide. No green color was observed, thereby eliminating biliverdin. Careful monitoring of food additives is warranted to prevent future problems in both animals and humans.