Physiological Properties of the Peritoneum in an Adult Peritoneal Dialysis Population over a Three-Year Period

Abstract

Objectives To describe the physiological properties of the peritoneal membrane in adult patients treated with peritoneal dialysis (PD) and to analyze the effects of patient characteristics and time. Design Observational study. Setting Department of Nephrology at the Sahlgrenska University Hospital. Method Peritoneal function was analyzed by the Personal Dialysis Capacity (PDC) test, based on the three-pore theory of capillary transport. The functional PDC variables are absorption, large-pore flow, and the area parameter (A0/Δx), which determines the diffusion of small solutes. The ultra-filtration (UF) coefficient is determined mainly by A0/Δx. Patients All patients ( n = 280) who had at least one PDC test done between September 1990 and August 1999. Results In 249 patients examined soon after start of PD, area was 19000 (SD 7100) cm2/cm/1.73 m2, large-pore flow 0.112 (SD 0.052) mL/min/1.73 m2, and the UF coefficient 0.071 (SD 0.032) mL/minute/mmHg/1.73 m2. Absorption was 1.54 (SD +2.64, –0.97) mL/min/1.73 m2. Large-pore flow was greater in patients with severe comorbidity than in patients with fewer comorbid conditions. Elderly patients had a lower UF coefficient than did younger patients ( p < 0.05). Repeated PDC tests were performed in 208 patients during a mean observation time of 18.4 months. There was a slight increase in the slope of the area-versus-time curve of 54 cm2/cm/1.73 m2 per month (approximately 10% after 3 years, p < 0.01); all other parameters remained constant. Conclusion Patient characteristics have an impact on peritoneal performance already at the start of dialysis. Peritoneal function can remain essentially stable during medium long-term PD.

Does Peritoneal Protein Transport Increase with Peritoneal Dialysis Therapy Duration and Lead to Extracellular Water Overload in Peritoneal Dialysis Patients?

“…Although this increasing D/S transporter status has been linked to previous peritonitis episodes , and changes in peritoneal membrane predisposing to encapsulating peritoneal sclerosis , it is now recognized that small pore transporter status does not increase in all PD patients over time . Similarly we found that for the whole group then over time peritoneal large pore flux, as determined by 4 h PET D/S total protein also remained stable, in keeping with previous reports , suggesting that there was no progressive change in the peritoneal membrane “leakiness” to larger molecules during the period of treatment with PD. If anything 4 h D/S protein was lower after 4 years, which may been due to a residual inflammatory effect due to the initial exposure to peritoneal dialysis fluids at the time of the first PET test.…”

“…At each time point we found a correlation between 4 h PET small pore and large pore transport. Some studies based on albumin measurements have suggested that peritoneal surface area may increase with duration of PD therapy, so that there could be some divergence between small and large pore transport . However, in our study for individual patients changes in the 4 h PET D/S creatinine were associated with similar changes in the same direction for the D/S total protein.…”

“…Previous studies, typically based on CAPD cohorts, have reported an association between faster transporter status and both PD technique failure and mortality , whereas other observational studies have linked faster transporter status to patient co‐morbidity and ECW over hydration . However, other reports have not shown the same associations between faster transporter status and outcomes , or ECW volume overload , but instead have noted associations between inflammation as assessed by increased serum CRP and reduced serum albumin concentrations and ECW excess .…”

“…As such this combination may have resulted in less ECW volume expansion and reduced exposure to glucose and glucose degradation products. Secondly we measured total protein, whereas previous studies relied on the peritoneal albumin measurements . Although there may potentially be differences between total protein and albumin peritoneal transport, it is more likely that studies which have measured peritoneal dialysate effluent albumin as a surrogate of protein transport could well be confounded by the bromocresol green method, which is recognized to be less accurate at lower albumin concentrations, and is prone to interactions with the globulin protein fraction .…”

“…Peritoneal protein clearance depends upon large pore fluid flux, which has been reported to increase with inflammation, patient age, co‐morbidities and generalized vascular disease . The importance of peritoneal dialysate protein losses, (predominantly albumin) remains unclear.…”