Metabolic Dysfunction-Associated Steatotic Liver Disease as a Risk Factor for Chronic Kidney Disease: A Narrative Review.

Metabolic dysfunction-associated steatotic liver disease (MASLD)-previously known as non-alcoholic fatty liver disease (NAFLD)-is currently the most common chronic liver disease globally. Observational studies have reported that MASLD is independently associated with extrahepatic disorders, such as chronic kidney disease (CKD). Severe forms of MASLD (i.e., steatohepatitis and liver fibrosis) are even more strongly associated with the risk of incident kidney dysfunction. Hypothetically, MASLD could directly promote CKD through liver-derived endocrine and metabolic mediators, hemodynamic alterations, immune-mediated mechanisms, and oxidative or cellular stress. However, proving that MASLD directly causes CKD is difficult due to the multiple shared cardiometabolic and systemic risk factors, such as obesity, hypertension, and type 2 diabetes mellitus, which serve as confounding variables. Moreover, studies on the association between MASLD and CKD have differed in their designs, sampling methods, disease definitions, and inclusion criteria, precluding more robust evidence supporting a causal relationship. Furthermore, few studies have explored specific issues, such as the new nomenclature for steatotic liver disease, the relationship between these diseases in pediatric populations, the impact of MASLD plus alcohol intake (MetALD) on CKD, and therapeutic options targeting MASLD and CKD simultaneously. Answers to these issues are essential, as the appropriate management of patients with MASLD may prevent or ameliorate kidney dysfunction. The aims of the present study are to describe shared risk factors between MASLD and CKD, the possible direct pathogenic effect of MASLD on kidney structure and function, and gaps in the current literature, to indicate future research directions.