Combination therapy with peritoneal dialysis and hemodialysis.

T he greatest benefit of peritoneal dialysis (PD) is the continuous nature of the therapy, which results in steady-state levels of electrolytes as well as fluid and acid–base balance. A continuous sodium removal reduces water intake and makes appropriate fluid management possible, even if the ultrafiltration (UF) volume is small. Peritoneal dialysis is also beneficial in maintaining residual renal function (RRF) (1,2), which is known to be a determinant of patient survival (3). Therefore, PD can easily deliver effective dialysis treatment that maintains the life of end-stage renal failure patients. Even though successful outcomes for PD in anuric patients have been reported (4), standard PD may not be sufficient to avoid the risk of uremic complications when RRF declines (5–7). Increasing the dose of dialysis, currently the only measure available to diminish these risks, has the potential to increase the negative impact of the dialysis solution. An alternative to increasing the dose of PD is to combine PD with hemodialysis (HD). Despite only limited outcome data being available, such a combined therapy has rapidly gained popularity in Japan. It is expected that, in 2002, approximately 5.5% of PD patients were prescribed PD + HD (8). McIntyre recently reported the results of a prospective study of such a combination therapy, PD + HD, referred to as bimodal dialysis, in 8 patients commencing dialysis (9). The objective of this combined therapy was to maximize solute removal and volume control. Patients were followed for at least 1 year. Their prescription consisted of highly efficient HD with a polysulfone membrane for 3 hours, at a dialysate flow rate of 750 mL/ minute, twice weekly, without UF, and low-dose daily PD with two exchanges of 2 L conventional solution and/or icodextrin-based dialysate to optimize water removal. In short, their dialysis prescriptions aimed to achieve solute clearance by PD and HD, and continuous water removal, thereby maintaining RRF. McIntyre reported good hemodynamic/volume control, reduced need for antihypertensive medication, and unchanged RRF. It is well known that RRF declines rapidly during conventional HD treatment (10,11). One of the reasons for this is thought to be the intermittent nature of HD resulting in rapid changes in patients' fluid status, suggesting that HD without UF could maintain RRF. The bimodal di-alysis method proposed by McIntyre is noteworthy in that it corrects this disadvantage of HD. However, this particular advantage is of no benefit once RRF is lost. In Japan, …