Myths in Peritoneal Dialysis

Martin B. Lee; Joanne M. Bargman


Curr Opin Nephrol Hypertens. 2016;25(6):602-608. 

In This Article

Myth 3: Peritoneal Dialysis Should Not Be Offered to Obese Patients Because Solute Clearance Will be Inadequate and Outcomes Will Be Worse Than in Nonobese Patients

In 2003, McDonald et al.[10] reported poorer outcomes for obese peritoneal dialysis patients in Australia and New Zealand. Almost a decade earlier, Nolph et al.[11] calculated theoretical body weight limitations to attaining a weekly Kt/V urea target of 1.7 in anuric CAPD patients performing four exchanges a day of 2, 2.5 and 3 l fill volumes to be 64, 77.6 and 91 kg, respectively. In current practice, the higher dialysate volumes deliverable with cycler-based regimens and additional clearance from residual renal function (RRF) may extend these weight limits. Importantly, Kt/V urea values may be falsely low in obese patients. Adipose tissue increases body weight and the numeric value of V without increasing the urea volume of distribution, because the water content of adipose tissue is low. Therefore, the equation Kt/V will be inaccurate, driven down by the weight of fat increasing the denominator. If a true Kt/V is warranted, fat-free body weight should be used to calculate V.

Short patients are presumed to have a smaller peritoneal surface area for solute clearance than tall patients at a given body weight; hence, KDOQI guidelines stated that marked obesity in short individuals is a relative contraindication to peritoneal dialysis.[5] Intriguingly, Snyder et al.[12] found a slight survival advantage for obese peritoneal dialysis patients in the first 2 years after initiating dialysis. These differences were observed according to intention-to-treat and the correlation between survival and clearance on peritoneal dialysis or after transfer to haemodialysis were not analysed. The authors commented that body mass index (BMI) should not be a dominant criterion for deciding between peritoneal dialysis and haemodialysis. In a recent 10-year single-centre retrospective cohort analysis of obese and nonobese peritoneal dialysis patients matched for age, sex and diabetic status, with similar Charlson comorbidity index and RRF, Ananthakrishnan et al.[13] observed that obese peritoneal dialysis patients weighing >=90 kg with BMI >=34 kg/m2 tended to have earlier and more frequent peritonitis but experienced fewer hospitalizations, fewer hernias and similar survival when compared with nonobese patients weighing <90 kg with BMI <25 kg/m2. Kt/V urea and delivered peritoneal dialysis volumes were similar in the two groups, and Cox regression analysis showed that weight and BMI were not associated with survival. Similarly, Fernandes et al.[14] reported that in 1911 incident peritoneal dialysis patients, obesity did not increase mortality in patients with BMI 25–29.9 kg/m2 and was in fact protective at BMI >30 kg/m2 during the first 34 months of dialysis.