Metastatic mineralization and renal intratubular crystals associated with hard drinking water in guinea pigs

This report describes cardiovascular and renal soft tissue mineralization and renal intratubular crystals in 13 out of 16 guinea pigs that were given very hard drinking water for 9 months. These animals, aged 14 to 20 months, were experimentally naïve. No clinical symptoms were observed, but 1 guinea pig was found dead in its cage. Necropsy did not reveal any gross findings; however, histologic examination revealed mineralization and crystal formations. Despite no known changes in the feed sourcing or formulation, the possibility that the incident was feed-related was considered. The most recent analysis of the feed obtained from the manufacturer during this period, which was conducted by an accredited laboratory authorized by the Ministry of Agriculture and Forestry, was appropriate. No similar lesions were reported at other centers using the same feed; however, drinking water analysis for total dissolved solids revealed extremely hard water, with elevated levels of calcium and calcium carbonate and low magnesium levels, due to a malfunctioning water treatment system. After installing a new system to balance calcium and magnesium, no new cases appeared over the next 2 years. It was determined that the mineralization and crystal formations were most likely caused by water hardness. This study demonstrates that mineralization typically attributed to feed in guinea pigs can also result from high calcium content in drinking water, highlighting the importance of water analysis in such cases.