Increased Water Viscosity Enhances Water Intake and Reduces Risk of Calcium Oxalate Stone Formation in Cats

SIMPLE SUMMARY: Increasing water intake and decreasing urine concentration are recommended for cats that form stony concretions in the bladder or urinary tract. The purpose of this study is to determine if water with increased viscosity results in increased water intake in cats by taking advantage of the unique anatomy of the cat’s tongue. Cats delicately dip their tongue into water, pull their tongues back up to their mouths, and capture the water that follows. Lapping occurs by fluid adhesion to the dorsal part of the tongue’s tip and by lifting a liquid column through the tongue’s upward motion before jaw closure. Cats have the ability to balance gravity and water surface tension to ingest the maximum amount of water per lap. This observation led us to question whether changing the properties of water in a way that allows cats to lift more water per lap is possible. Increasing the viscosity of water was accomplished with 1% methylcellulose, an ingredient that is palatable to cats. Cats consuming 1% methylcellulose water had increased water intake (25% and 21% higher at 28 and 56 days, respectively), and increased water intake reduces the risk for calcium oxalate stone formation. The benefit of giving cats viscous water is that they can increase water consumption without having to change their natural drinking behavior. ABSTRACT: The purpose of this study is to determine if water with increased viscosity results in increased water intake, thus lowering the risk of urolithiasis in cats. Twelve healthy adult cats were fed pre-trial standard dry maintenance food for 1 week and then randomized into two groups for the study phase. The cats continued to receive the same food but were provided either control (deionized) water or viscous (1% methylcellulose) water for two months and then switched to the other water type for two months in a cross-over study design with repeated measures. Complete blood counts, serum chemistry profiles, and urinalysis were performed at the initiation of the study and again at 1, 2, 3, and 4 months. Daily water consumption and energy intake for each cat were recorded. Body weights were assessed weekly. Cats consuming 1% methylcellulose water with increased viscosity had increased water intake (p < 0.001; 25% and 21% higher at 28 and 56 days, respectively). Increased consumption of water resulted in lower urine specific gravity (p = 0.04), serum creatinine (p = 0.02), and blood urea nitrogen (p = 0.002) concentrations (without changing serum albumin, glucose, and calcium concentrations or serum osmolality) and decreased urine calcium concentration (p = 0.01) compared with cats consuming control water. In addition, the increased water intake increased (p = 0.05) resistance to oxalate crystal formation.