M AMER, E TAN, G WATERS
Regional Renal Unit, Waikato Hospital, Hamilton, New Zealand
Aim: To investigate the effect of body weight (BW) on Peritoneal Dialysis (PD) outcomes.
Background: The effects of obesity in PD remain unclear, with conflicting literature results. Previous studies used obesity measures (body mass index and body surface area) but crucial data for calculations is often incomplete in electronic records. This study investigated how BWs alone relate to PD outcomes: patient survival (PS), peritonitis-free survival (PFS) and technique survival (TS).
Methods: Demographics data (weight categories, age, sex, diabetes, ethnicity and clearance for all patients and patients ≥100kg) were extracted from the NZPD Registry for adults starting PD from 2005-2015. Outcomes were compared across weight ranges <50,50-100,100-120,>120kg for PS (excluding patients ceasing PD <90 days), PFS and TS (both censored for withdrawals, transplantation and deaths). Data was statistically analysed using Log-rank, Chi-squared and t-test.
Results: Across categories (<50,50-100,100-120,>120kg), weight distribution was (4%/89%/6%/1%) with mean weight ± standard deviation (75.2±16.1kg). There were 2589 total patients versus 167 heavy patients (≥100kg): mean age (58.1±13.7years versus 54.9±11.2years, p=0.0032), male ratio (58% versus 66%, p=0.0307), diabetics (57% versus 69% p<0.0001), European/Maori/Other ethnicity (41%/30%/29% versus 28.1%/44.3%/27.5%, p=0.0010/0.0001/0.6786), mean Kt/V (2.1±0.5 versus 1.8±0.4, p<0.0001). Outcomes for <50,50-100,100-120,>120kg categories: median PS (4.09,4.45,4.96,3.68years; p=0.5), median PFS (2.45,1.79,1.63,0.70years; p=0.269) and median TS (4.07,4.28,3.36,2.81years; p<0.001).
Conclusions: PD TS worsened with increasing BWs whilst PS and PFS appeared unchanged. Heavier patients (≥100kg) were more likely to be male, diabetic, Maori, have lower clearances and less likely European. BW alone may be a useful marker for PD outcomes. Novel body mass measurements (muscle mass estimation and body composition bio-impedance based measurements) may be even more accurate. Further studies could include prospective observational analysis of matched patients on haemodialysis.