The prevalence of chronic kidney disease (CKD), generally defined as a long-standing, irreversible impairment of kidney function, is substantially greater than the number of pts with end-stage renal disease (ESRD), now ≥500,000 in the United States. There is a spectrum of disease related to decrements in renal function; clinical and therapeutic issues differ greatly depending on whether the glomerular filtration rate (GFR) reduction is moderate (stage 3 CKD, 30-59 mL/min per 1.73 m²) (see Table 46-1. ), severe (stage 4 CKD, 15-29 mL/min per 1.73 m²), or “end-stage renal disease” (stage 5 CKD, <15 mL/min per 1.73 m²). Dialysis is usually required once GFR <10 mL/min per 1.73 m². Common causes of CKD are outlined in Table 139-1.