Artificial and biological membranes in acute kidney injury: a biomedical engineering framework on renal replacement therapy in critical care

Background: Acute kidney injury (AKI) is a common complication in critically ill patients and frequently requires renal replacement therapy (RRT). While comparisons between continuous renal replacement therapy (CRRT) and peritoneal dialysis (PD) have traditionally focused on clinical efficacy, less attention has been given to the membrane technologies underlying these modalities. This narrative review compares synthetic membranes used in extracorporeal therapies with the biological peritoneal membrane from a biomedical engineering perspective.

A narrative review of the literature was conducted, integrating evidence from nephrology, critical care medicine, biomaterials science, and biomedical engineering. The review examines membrane transport mechanisms (diffusion, convection, ultrafiltration, and adsorption), membrane biocompatibility, transport behavior during critical illness, and emerging bioartificial renal technologies.

Although synthetic and biological membranes rely on the same fundamental transport principles, they differ markedly in structure and function. Synthetic membranes provide predictable and controllable transport but are affected by blood-material interactions and membrane fouling. In contrast, the peritoneum is a living, adaptive membrane whose transport properties are influenced by vascular physiology, systemic inflammation, and endothelial integrity. These differences reflect distinct engineering approaches underlying CRRT and PD.

A membrane engineering perspective provides a unified framework for comparing RRT modalities beyond conventional clinical outcomes. Artificial membranes emphasize precision and reproducibility, whereas biological membranes offer physiological integration and adaptability. Future renal support systems are expected to combine these complementary properties through hybrid technologies that more closely replicate native kidney function.