Properties of uremic solutes that allow their effective control by peritoneal dialysis

BackgroundAt low levels of kidney function, uremic symptoms prompt the initiation of dialysis. Peritoneal dialysis can continue to relieve these symptoms even when patients become anuric. To accomplish this, dialysis must maintain the plasma levels of solutes which cause symptoms lower than they were when dialysis was initiated. This study examined kinetic properties that solutes must possess for peritoneal dialysis to accomplish this. We sought further to identify solutes that possess these properties.MethodsMathematical modeling analyzed kinetic properties that determine a solute's plasma level in an anuric dialysis patient relative to its level when symptoms prompt dialysis initiation. The predictions of modeling were compared to the observed behavior of the solutes methylurea, guanidine, and phenylacetylglutamine measured in 22 patients on peritoneal dialysis and 22 patients with advanced chronic kidney disease using liquid chromatography tandem mass spectrometry.ResultsModeling showed that peritoneal dialysis can effectively control the plasma levels only of solutes which have a high dialytic clearance relative to their native kidney clearance. Chemical measurements showed that the dialytic clearance of methylurea was close to that of urea while the dialytic clearances of guanidine and phenylacetylglutamine were lower. Comparison of these dialytic clearances with residual native kidney clearances suggested that if their generation rates remained stable, peritoneal dialysis could control the levels of methylurea but not guanidine or phenylacetylglutamine in anuric patients.ConclusionA search for solutes whose properties include a high dialytic clearance and a relatively low native kidney clearance could identify solutes that contribute to uremic symptoms.