Figure 1.

Five-stage classification system for CKD. During the progression of CKD, the decrease in kidney function, evaluated by the glomerular filtration rate (GFR), leads to a variety of disturbances in body homeostasis. The accumulation of uremic toxins, the increase in signs of volume overload, the worsening of hypertension, and the induction of metabolic and hormonal disturbances are typical of CKD patients. The progression of CKD often leads to a decline in residual renal function (RRF), eventually leading to renal replacement therapy (i.e., haemodialysis, peritoneal dialysis, and kidney transplantation).