Personal daily dialysis: the evolution of the artificial kidney.

To improve hemodialysis (HD) patients' clinical tolerance and quality of life, a new paradigm of technological evolution of the artificial kidney needs to be addressed at this point. Compared to the second law of thermodynamics, if HD is a barrier against entropy increase, personal daily dialysis (PDD), taking account of multidimensional treatment parameters specific to the patient, can be a new treatment option. Here, we review currently used HD equipment and competing technologies of the wearable artificial kidney (WAK) for future application to PDD. Biofeedback control during HD personalizes treatment parameters such as blood volume changes, thermal energy balance and biochemical variables in well-defined ranges and tries to deliver the targeted treatment dose without intradialytic hypotension. Miniaturized devices such as WAK could also meet the needs of patients by providing mobility, the possibility of normal social activities and flexibility of treatment schedule. So far, many studies have shown the future direction of renal replacement therapy for chronic patients: personalization and daily treatment. PDD might require a new index including a biological plan for recovery of homeostasis and a strategy toward long-term rehabilitation of the patient. The concept of entropy includes these multidimensional factors, and the artificial kidney should be evolved to minimize the increase in entropy of the patient.