title: Predicting the crystallization potential of urine from cats and dogs with respect to calcium oxalate and magnesium ammonium phosphate (struvite).
abstract: The objective of this study was to validate two programs (SUPERSAT and EQUIL 2) for calculation of calcium oxalate (CaOx) and magnesium ammonium phosphate (struvite; MAP) relative supersaturation (RSS) in dog and cat urine. Healthy adult cats (n = 10) and dogs (n = 9) were fed standard diets for a 3-wk period. Urine was collected (24 h, dogs; 48 h, cats) and filtered, and the pH was measured. A 20-mL aliquot was titrated to pH 2 and frozen for analysis. Additional aliquots were incubated with 1 g seed crystals at 38 degrees C; CaOx for 24 h (cat) and 2, 6 and 9 d (dog); MAP for 48 h (dog) and 6 d (cat). Samples were analyzed for 10 substances. RSS was calculated using EQUIL 2 and SUPERSAT. CaOx RSS (SUPERSAT): dog urine was initially supersaturated, whereas cat urine was undersaturated with the diets used. Cat urine reached the solubility product (K(sp)), (RSS = 1) after 24-h incubation, whereas dog urine was still approaching K(sp) at 9 d. MAP RSS (SUPERSAT): urine from both species was undersaturated and increased toward K(sp) during incubation. Final RSS values were compared for both programs. SUPERSAT resulted in values close to 1 for both CaOx and MAP; EQUIL 2 gave similar values for CaOx RSS, although MAP RSS values were considerably higher than 1. In conclusion, EQUIL 2 and SUPERSAT both calculated reasonably accurate RSS values for CaOx, whereas only SUPERSAT provided an accurate measure of MAP RSS.
authors.affiliation: Centre for the Prevention and Treatment of Urinary Stones, Institute of Urology and Nephrology, London, UK and. Waltham Centre for Pet Nutrition, Leicestershire, UK.
authors.forename: William G
authors.initials: WG
authors.lastname: Robertson
authors.forename: Julie S
authors.initials: JS
authors.lastname: Jones
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Heaton
authors.forename: Abigail E
authors.initials: AE
authors.lastname: Stevenson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Markwell
mesh_terms: D000818:Animals; D002129:Calcium Oxalate / Q000652:urine*; D002415:Cats / Q000652:urine*; D003460:Crystallization; D004285:Dogs / Q000652:urine*; D005260:Female; D005544:Forecasting; D017616:Magnesium Compounds / Q000652:urine*; D008297:Male; D010710:Phosphates / Q000652:urine*; D012984:Software / Q000592:standards; D012995:Solubility; D000069877:Struvite; D014556:Urine / Q000737:chemistry
chemical_list: D017616:Magnesium Compounds; D010710:Phosphates; D002129:Calcium Oxalate; D000069877:Struvite