Impact of combination therapy with peritoneal dialysis and hemodialysis on peritoneal function.

Peritoneal dialysis (PD) is a continuous, slow dialysis method advantageous for retaining residual renal function; however, after renal function is lost, increasing the PD dose is difficult, resulting in insufficient dialysis. The addition of hemodialysis (HD) to PD [combination therapy with PD and HD (PD+HD)] increases the ultrafiltration volume and optimizes the dialysis dose. Based on this situation, we have applied concomitant HD after loss of residual renal function in PD patients. In the present study, we investigated peritoneal function in patients who underwent PD+HD therapy. The subjects were 76 patients in whom PD+HD therapy continued for 6 months or longer. In PD+HD therapy, patients underwent PD 6 days each week and a 4-hour HD session once each week. The patients were divided into four groups based on their dialysate-to-plasma ratio of creatinine (D/P Cr) in a peritoneal equilibration test (PET) at the initiation of PD+HD therapy: high [H (n = 5)], high-average [HA (n = 29)], low-average [LA (n = 26)], and low [L (n = 16)]. Before and after initiation of PD+HD therapy, we measured PET D/P Cr values and effluent levels of fibrin degradation products (eFDPs) and cancer antigen 125 (eCA125) in the 4-hour PET effluent. In addition, we evaluated the ratio of overnight effluent to serum beta2-microglobulin (overnight D/P beta2MG) every year. In the H group, D/P Cr remained high after initiation of PD+HD therapy, but it declined significantly in the HA group and tended to decline in the LA and L groups. Overnight D/P beta2MG remained high in the H group after PD+HD therapy, but significantly declined in the HA group and remained unchanged in the LA and L groups. After PD+HD therapy initiation in the H group, eFDPs declined markedly, although that change was not significant. No decrease was noted in any other group. Peritoneal dialysis was discontinued in 33 of the 76 patients (43.4%) who underwent PD+HD therapy: in 5 of the 5 patients in the H group (100%), in 16 of 29 in the HA group (552%), in 7 of 26 in the LA group (26.9%), and in 5 of 16 in the L group (31.3%). On long-term follow-up, the PET D/P Cr tended to decrease in the H and LA groups; it did not change in the LA and L groups. No significant changes were noted in any group for overnight D/P beta2MG, eFDPs, or eCA125. We suggest that concomitant HD facilitates the continuation of PD treatment and the retention of peritoneal function in patients with uremic symptoms and excess body fluid associated with a loss of residual renal function. However, improvement in peritoneal function cannot be expected for patients in whom peritoneal function has already deteriorated. In those patients, a change of treatment method should be considered.