Current insights into the mechanisms and management of infection stones

Infection stones are complex aggregates of crystals amalgamated in an organic matrix that are strictly associated with urinary tract infections. The management of patients who form infection stones is challenging owing to the complexity of the calculi and high recurrence rates. The formation of infection stones is a multifactorial process that can be driven by urine chemistry, the urine microenvironment, the presence of modulator substances in urine, associations with bacteria, and the development of biofilms. Despite decades of investigation, the mechanisms of infection stone formation are still poorly understood. A mechanistic understanding of the formation and growth of infection stones — including the role of organics in the stone matrix, microorganisms, and biofilms in stone formation and their effect on stone characteristics — and the medical implications of these insights might be crucial for the development of improved treatments. Tools and approaches used in various disciplines (for example, engineering, chemistry, mineralogy, and microbiology) can be applied to further understand the microorganism–mineral interactions that lead to infection stone formation. Thus, the use of integrated multidisciplinary approaches is imperative to improve the diagnosis, prevention, and treatment of infection stones. In this Review, the authors describe the current mechanistic understanding of infection stone formation and growth, including the influence of the organic matrix, microorganisms, and biofilms, highlighting the medical implications of these insights and the importance of multidisciplinary management approaches. Key points Urine chemistry has a key role in infection stone formation and is determined by the saturation conditions, pH, and the presence of modulators of crystallization and aggregation in the urine. Organic substances associated with infection stones influence their physical characteristics (for example, hardness) and could also be involved in stone formation. Struvite stones are associated with urinary tract infections and are formed as a result of biomineralization by urea-hydrolysing microorganisms. Positive stone cultures suggest the association of bacteria with calcium-based stones; however, the role of bacteria (active or passive) in the lithogenesis of calcium-based stones requires further examination. The development of microbial biofilms complicates renal conditions and treatments; biofilm mechanical stability and resistance to treat