The amount of dialysis that a patient receives can impact morbidity and mortality [1,2]. Thus, two central issues in the management of patients undergoing maintenance hemodialysis include determining the optimal amount of dialysis that should be prescribed and quantifying the amount of dialysis that is actually delivered to individual patients.
Improvement in patients' symptoms and the blood urea nitrogen (BUN) concentration are not accurate measures of dialysis adequacy for two reasons:
●The dialysis dose that reduces uremic symptoms is lower than the dose shown to increase survival. This is especially true when erythropoietin is started concurrently with dialysis for anemia, since many symptoms attributed to uremia are actually related to anemia. (See "Erythropoietin for the anemia of chronic kidney disease among predialysis and peritoneal dialysis patients" and "Erythropoietin for the anemia of chronic kidney disease in hemodialysis patients".)
●The BUN depends on factors that are independent of the dialysis dose, such as protein intake, protein catabolic rate, and residual renal function. A low BUN may reflect inadequate nutrition rather than sufficient dialytic urea removal.
All methods used to measure dialysis dose are based upon urea clearance. Although the best method is not known, the Kt/V is used by most nephrologists. This topic reviews the Kt/V and other methods that are used to measure the amount of dialysis delivered to individual patients. We also discuss dialysis dose recommendations for hemodialysis patients. Assessing the adequacy of peritoneal dialysis is discussed elsewhere (see "Adequacy of peritoneal dialysis" and "Why Kt/V and creatinine clearance may not correlate in continuous peritoneal dialysis" and "Problems with solute clearance and ultrafiltration in continuous peritoneal dialysis"). Patient outcomes related to dialysis are discussed elsewhere. (See "Patient survival and maintenance dialysis" and "Dialysis modality and patient outcome".)