The Concept of Adequacy in Peritoneal Dialysis

The aim of renal replacement therapy is to obtain blood purification from metabolic waste products sufficient to achieve patient rehabilitation, the control of dry body weight, and the correction of acid base and electrolyte imbalances (1–3). Among these, the correction of the hormonal imbalances as a result of renal disease would also be required (4). However, this is difficult to achieve, and the majority of substitute therapies such as hemodialysis and peritoneal dialysis focus on blood purification and fluid and electrolyte homeostasis. For this reason the search for the optimal dialytic therapy has been limited to the possibility of achieving a treatment that could at least be adequate in terms of blood purification and patient rehabilitation. Therefore, dialysis adequacy has been selected as a term to indicate successful renal replacement therapy, one that could overcome most of the uremic symptoms and allow the patient to reach a sufficient degree of rehabilitation, even though the treatment is far from the complete and optimal substitution of the lost kidney function in its whole. In recent years the concept of dialysis adequacy has been studied by several authors, and a continuous evolution of this concept has been observed. From the original description of the square-meter-hour hypothesis of Babb and Scribner in 1971 (5), a series of new studies led to the clinical application of various indices devoted to describing the level of efficiency achieved by dialysis treatment (6,7). Finally, after the American National Cooperative Dialysis Study was analyzed, and the KTN index was selected as a marker for dialysis adequacy, the majority of authors now rely on this index and are proposing various formulas for its calculation (8–11).