Salivary Metabolomic Profile in Individuals with Different Stages of Renal Function: A Scoping Review ^†

Introduction: Saliva is a complex biofluid with multiple physiological roles and a rich molecular composition, including proteins, metabolites, microorganisms, immune cells, lipids, enzymes, and other compounds. Due to this molecular diversity, saliva has emerged as a valuable source of biomarkers for both oral and systemic diseases, including kidney dysfunction—a growing public health concern that affects twice as many individuals as type 2 diabetes. As a diagnostic medium, saliva offers several advantages: it is non-invasive, painless, and easy to collect, making it a practical alternative to blood and urine. This scoping review aimed to map and synthesize the existing literature on the salivary metabolomic profile of individuals with kidney dysfunctions, highlighting knowledge gaps and opportunities for future research. Methodology: This review followed the PRISMA-ScR guidelines and was registered in the Open Science Framework. Searches were conducted in nine databases up to 27 November 2024. The methodological quality of the included studies was assessed using SANRA, STROBE, and the Newcastle–Ottawa Scale. Results: A total of 2864 records were retrieved, and after duplicate removal and blinded peer screening, 17 studies met the eligibility criteria. The selected studies were primarily cross-sectional, along with nephrology conference abstracts, one cohort study, and one narrative review. Conclusions: Overall, salivary metabolomics demonstrated promising potential in identifying biomarkers related to renal function.