Abstract
Urinary tract diseases are a common concern in domestic cats and a leading cause of veterinary visits. Urolithiasis is a major contributor to discomfort, clinical signs, and secondary complications, negatively impacting feline health and welfare. Diet is a manageable risk factor that can be leveraged in commercial formulations to support urinary tract health and reduce urolith risk, particularly struvite. Nutritional interventions primarily influence three interrelated determinants of urolith formation: urinary pH, urine solute concentrations, and crystallization potential. Controlled dietary acidification is central to struvite prevention, supporting the controlled use of urinary acidifier agents in cat food (eg DL methionine, sodium bisulfate, phosphoric acid, calcium sulfate) as an effective strategy. While the prevalence of struvite stones in cats declined from the mid-1980s to the 2000s as scientific knowledge of such dietary strategies in commercial cat food has evolved, recent U.S. reports show an increase in struvite stones, warranting attention to the potential impact of commercial diets on this outcome. Regarding urinary acidifier agents, excessive intake of certain compounds (eg inorganic phosphorus or DL-methionine) raises potential long-term health concerns. At the same time, "clean label" trends may discourage efficacious acidifiers with no health concerns, including sodium bisulfate, which can both acidify urine and, via its sodium content, support water intake. Predictive equations can help estimate urinary pH during cat food formulation. Still, they do not capture critical factors, such as water intake and feeding behavior. Consequently, in vivo evaluation remains the gold standard, albeit costly and time-consuming, making it challenging for universal adoption in the industry. Additional challenges faced by the sector include variability in mineral composition across ingredients, limited data on mineral bioavailability, nutrient interactions, and other factors that affect the post-prandial concentrations of specific minerals known to impact urolith formation. This review discusses the etiology of feline urolith formation, evidence-based dietary interventions, and the efficacy and systemic effects of commonly used urinary acidifier agents, as well as challenges in formulating commercial cat foods targeting urinary tract health, including precise nutrient balancing and regulatory considerations to support urinary tract health claims.