Neutrophil Extracellular Traps Promote Urolithiasis Formation in Dogs: A Preliminary Study

Canine urolithiasis is a common and highly recurrent urinary tract disease, with struvite and calcium oxalate being the predominant stone types. Stone formation has traditionally been attributed to urinary physicochemical factors, including urine pH, mineral supersaturation, and urinary tract infection. However, these factors alone cannot fully explain the persistent growth and rapid progression of stones in affected dogs. In this study, we provide evidence that innate immune mechanisms, particularly neutrophil extracellular traps (NETs), are associated with canine urolith formation. We found that neutrophils, key cells of the innate immune system, release neutrophil extracellular traps composed of DNA and antimicrobial proteins, which are consistently present within urinary stones and their surrounding microenvironments. Common canine urinary pathogens were shown to trigger this response, and these immune-derived structures promoted crystal nucleation, aggregation, and stone growth in experimental systems. Importantly, enzymatic degradation of NETs by DNase I attenuated NET-associated stone growth under in vitro conditions. These findings suggest that canine urinary stones develop not only as a consequence of physicochemical factors, but also in association with inflammation-driven biomineralization processes involving NETs. Recognizing the contribution of innate immunity provides new insight into stone recurrence and may inform future preventive and therapeutic strategies.