A prospective study of peritoneal transport in CAPD patients

Abstract

A prospective two year follow-up study of the functional characteristics of the peritoneal membrane was conducted in 61 CAPD patients. Peritoneal transport of solutes, calculated by mass transfer area coefficients for urea and creatinine, peritoneal clearances for proteins, percentage of absorption of glucose, as well as net ultrafiltration were measured every four months. After five months on CAPD a decrease was found for the transport of most solutes (P < 0.05, mean values, ml/min/1.73 m2): urea 18.1 to 16.2, creatinine 9.5 to 8.4, IgG 0.049 to 0.040 and alpha 2-macroglobulin 0.020 to 0.015, as well as for the absorption of glucose (57.9 to 53.2%, P < 0.05). Net ultrafiltration increased simultaneously from 44.6 to 100.5 ml/4 hr/1.73 m2, P < 0.05. From five months to two years on CAPD a significant increase in the transport of all solutes except alpha 2-macroglobulin was found, as well as a decrease in net ultrafiltration. Peritoneal transport at the end of the study was not significantly different from the starting values. Our findings indicate an initial effect of CAPD itself on peritoneal transport, probably due to the recent start of the treatment. Baseline values were reached after five months on CAPD. Thereafter a gradual increase in peritoneal solute transport occurred during two years of treatment. This can be explained by an increase in the effective peritoneal surface area.

Longitudinal Study of Small Solute Transport and Peritoneal Protein Clearance in Peritoneal Dialysis Patients

“…There are several possible explanations. First, a relationship with increasing age, as described previously (8)(9)(10), was seen in the patients treated for 2 and 3 years (see Supplemental Table 2), and this could account for some hidden association with comorbid disease. Second, this is a deliberately selected patient cohort and patients with more serious comorbidity-or specific types, such as peripheral vascular disease-were under-represented.…”

“…This relative reduction in large-pore area could reflect many processes, including a resolution of the early inflammatory state of the membrane after the start of PD. Several studies have also shown that depending on when the initial membrane function tests are done, PSTR also decreases in the months after PD is established before the longer-term increase (10,(18)(19)(20)(21). Alternatively, it could mean that large pores are underrepresented in newly formed vessels (surprising because new vessel formation in diabetic nephropathy is associated with increased protein extravasation) or that interstitial and perivascular fibrosis, known to occur over time (1), is impeding large-pore leak through the interstitial structures.…”

“…Longitudinal changes in protein clearance, predominantly a reflection of hydrostatic pressuredriven leak of plasma proteins through the large-pore pathway, are less clear. Cross-sectional and longitudinal studies (7)(8)(9)(10) have suggested that this does not necessarily increase with time on treatment, but it is not clear whether this represents a real difference from the observed changes in the PSTR. This is further confused by the observation that peritoneal protein clearance (Pcl) is associated with increased age and comorbidity at the start of treatment.…”

Relationship between peritoneal permeability with inflammation and subclinical atherosclerosis in peritoneal dialysis patients

“…Moreover, malnutrition and chronic inflammation are prevalent in high transporters (29)(30)(31)(32). Low serum albumin level correlates with malnutrition (28) and is strongly predictive of PD patient mortality (29,30). The greater prevalence of hypo-albuminemia in high transporters may also arise from hemo-dilution secondary to suboptimal ultrafiltration (31) or from excessive peritoneal protein losses (32).…”

“…Previous reports showed high transport status to be associated with poor survival in PD patients (11,28). Moreover, malnutrition and chronic inflammation are prevalent in high transporters (29)(30)(31)(32). Low serum albumin level correlates with malnutrition (28) and is strongly predictive of PD patient mortality (29,30).…”