The future of renal replacement therapy.

The worldwide epidemic of chronic kidney disease shows no signs of abating in the near future. Current dialytic forms of renal replacement therapy (RRT), even though successful in sustaining life and improving quality of life somewhat for patients with end-stage renal disease, have many limitations that result in still unacceptably high morbidity and mortality. Transplantation is an excellent option but is limited by the scarcity of organs. An ideal form of RRT would mimic the functions of natural kidneys and be implantable, safe, and cost-effective. Until recently, these goals would have been hard to achieve, but with the application of nanotechnology and microfluidics to RRT, they appear closer than ever before. Newer approaches include the human nephron filter (HNF), a novel form of RRT consisting of 2 membranes in series. The first membrane mimics the function of the glomerulus, and the other membrane mimics the function of the tubule. Investigators have proposed the synthesis of a silicone membrane that more closely resembles the glomerular filtration membrane and the use of a membrane with implanted renal tubular cells to provide tubular and other kidney functions. Membraneless dialysis that utilizes the principle of microfluidics has been proposed. Application of microelectromechanical systems (MEMS) technology will provide the ideal miniature detection system for future implantable dialysis devices. Finally, stem cells hold much promise, both for kidney disease and as a source of tissues and organs. In summary, nephrology is at an exciting crossroad with the application of innovative and novel technologies to RRT that hold considerable promise for the near future.