The gut-kidney axis in pediatric acute kidney injury: a review of pathophysiological mechanisms and therapeutic frontiers.

Acute kidney injury (AKI) is a frequent and severe condition in hospitalized children, leading to significant morbidity, mortality, and long-term risk of chronic kidney disease. This review explores the gut-kidney axis, a concept describing the bidirectional relationship between the gut microbiome and kidney function, as a critical driver of pediatric AKI. In critically ill children, interventions such as broad-spectrum antibiotics and necessary nutritional support strategies (e.g., parenteral nutrition or fasting) can cause profound gut microbial imbalance (dysbiosis). This dysbiosis initiates a deleterious feedback loop, exacerbating kidney injury. Key mechanisms include the disruption of the intestinal barrier (leaky gut), which allows bacterial endotoxins to enter the bloodstream, triggering renal inflammation via Toll-like receptor 4 signaling. Concurrently, the dysbiotic gut increases production of directly nephrotoxic gut-derived uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, while failing to produce protective anti-inflammatory metabolites like short-chain fatty acids. While therapies targeting the microbiome, such as probiotics, prebiotics, and fecal microbiota transplantation, are theoretically promising, their clinical use in pediatric AKI is unsupported by evidence and carries substantial risks, particularly iatrogenic infection. A significant knowledge gap exists due to a relative lack of pediatric-specific clinical research. The conclusion emphasizes an urgent need for longitudinal, multi-omics studies in children to understand this axis, identify functional biomarkers, and develop safe, targeted therapies to improve outcomes.