Table 1 lists baseline characteristics of 176 patients with incident PD (mean age, 60 ± 15 years; male, 71%). Causes of ESRD comprised chronic glomerulonephritis (CGN) in 56 patients (32%), diabetes in 66 (38%), hypertension in 27 (15%), polycystic kidney disease (PKD) in 5 (3%) and other or unknown in 22 (13%). Prevalences of cardiovascular disease, cerebrovascular disease and malignant disease were 12%, 9% and 6%, respectively. At the start of PD, urine volume, urea nitrogen and serum creatinine were 1230 mL/day (IQR 980–1800), 79.7 ± 28.6 mg/dL and 8.9 ± 2.4 mg/dL, respectively. Regarding PD-related tests, total, renal and PD Kt/V were 1.67 ± 0.49, 0.82 ± 0.41 and 0.84 ± 0.34, respectively. Baseline D/P Cr obtained from the PET was 0.60 ± 0.12.
Median follow-up was 41 months (IQR, 25–67 months). Among the 176 enrolled patients, 82 patients were transferred from PD alone to other modalities, comprising 47 patients transferred to combined therapy with PD and HD and 35 patients directly transferred to HD, with times to transfer of 28 months (17–44 months) and 33 months (16–45 months), respectively. Among the 47 patients who transferred to combined therapy, 22 patients subsequently transferred to HD alone. Patients transferred to combined therapy were younger and had a higher body mass index (BMI) than those directly transferred to HD or those who continued PD alone, whereas no significant differences in other clinical parameters at the start of PD were seen between the three groups (Table 1). Reasons for changes in dialysis modalities are shown in Fig. 1. Among the patients transferred to combined therapy, 66% transferred because of inadequate dialysis, fluid overload or both, whereas only 29% transferred because of these reasons among the patients directly transferred to HD (P < 0.01, Chi-squared test). Other reasons included inguinal hernia operation (n = 1), exit-site infection (n = 1), preparation for renal transplantation (n = 1), initiating dialysis with combined therapy (n = 1) and unknown reason (n = 12) among patients transferred to combined therapy, and difficulty performing PD (n = 7), pleuroperitoneal communication (n = 4), peritonitis (n = 4), exit-site infection (n = 3), abdominal disorder or surgery (n = 3) and unknown reason (n = 4) among those directly transferred to HD. Regarding dialysis prescription, 93% of patients on combined therapy received 4-h HD using high-flux dialyzers once weekly, whereas the remaining 7% received 4-h online hemodiafiltration once weekly. In general, PD was not carried out on the day of the HD session, and 35% of patients also did not perform PD on some other day each week, defined as a ‘PD holiday’.
Table 2 shows comparisons of changes in clinical and biochemical parameters between patients transferred to combined therapy and those directly transferred to HD. BMI and urinary volume decreased after changing dialysis modalities in both groups. Urea nitrogen and serum creatinine decreased among patients directly transferred to HD, whereas no significant change was apparent among those transferred to combined therapy. BP decreased among patients transferred to combined therapy, but did not change significantly among those directly transferred to HD. Hemoglobin levels increased among patients transferred to combined therapy, whereas they no significant change was seen among those directly transferred to HD. Serum albumin and β2 microglobulin did not change significantly in either group. Overall, degrees of change in diastolic BP, urea nitrogen and serum creatinine were significantly different between groups (repeated-measured ANOVA P = 0.03, P < 0.01 and P < 0.01, respectively).
Thirty deaths occurred during follow-up (median, 41 months), including 11 cardiovascular deaths. One patient died after transfer to combined therapy, 5 patients died after transfer to HD alone and the remaining 24 patients died during PD therapy alone. Figure 2 shows a Kaplan-Meier analysis comparing patient survival between these three groups. (log-rank P < 0.01). Nineteen patients were censored due to renal transplantation and the median follow-up for that group was 13 months. Mortality was highest among patients continuing PD and was lower among those switching to combined therapy was among those switching directly to HD. Among patients switching dialysis modality because of inadequate dialysis and/or fluid overload, 1 patient died after transfer to combined therapy and 1 patient died after transferring directly to HD alone. Kaplan-Meier analysis revealed no differences in patient survival between these two subgroups (log-rank P = 0.18, Fig. 3).