Peritoneal morphology after long-term peritoneal dialysis with biocompatible fluid: recent clinical practice in Japan

Abstract

Background: Morphology changes of the peritoneal membrane after long-term peritoneal dialysis (PD) consist of denudation of peritoneal mesothelial cells, interstitial sclerosis, and hyalinizing vasculopathy. Those changes are considered to be the result of uremia and bioincompatible effects of conventional acidic lactate-buffered dialysate with glucose degradation products (GDPs). In the last decade, biocompatible dialysate with neutral pH and low GDPs has become widely used. Clinical practice has been modified in Japan, especially for anuric patients, and now includes the use of hybrid therapy. The impact on peritoneal morphology has not been well reported.

Objective: The aim of the present study was to investigate the long-term effect on peritoneal morphology and function of biocompatible fluid use and current clinical practice in Japan, including hybrid dialysis therapy.

Methods: We evaluated peritoneal biopsy specimens from patients who had undergone PD for more than 3 years. We used the average peritoneal thickness (APT) of the submesothelial compact zone as a marker of interstitial sclerosis and the lumen/vessel diameter ratio (L/V ratio) at postcapillary venules as a marker of hyalinizing vasculopathy. Demography and other data for the patients, including dialysate-to-plasma (D/P) ratio of creatinine, were obtained at baseline and every 6 months by peritoneal equilibration test.

Results: Between 2002 and 2009, 110 patients started PD therapy with biocompatible dialysate at Tokyo University Hospital. Among them, 11 patients (8 men, 3 women; age: 54.2 ± 11.8 years; 1 with diabetes mellitus) were enrolled into this morphology study. The mean duration of PD in this group was 61 ± 11.3 months, and the mean time to peritoneal biopsy was 58 ± 15.1 months. The median APT was 180 μm (96 - 1424 μm), and the median L/V ratio was 0.66 (0.46 - 0.74). No obvious correlations between APT, L/V ratio, and PD duration were detected. The D/P creatinine of the 11 patients was maintained at a favorably low value, comparable with that of the other 99 patients.

Conclusions: Peritoneal dialysis therapy using biocompatible dialysate in conjunction with modification of clinical practice may minimize the progression of peritoneal interstitial sclerosis and hyalinizing vasculopathy, preserving favorable peritoneal function for more than 3 years.

Figure 1

— Evaluation methods for peritoneal sclerosis. (A) Average peritoneal thickness (APT) by the 5-point measurement method. Peritoneal thickness is measured at 5 randomly selected points, and the APT is then calculated. In this peritoneal dialysis patient (number 10), peritoneal thicknesses ranged from 155 μm to 259 μm. The APT was calculated to be 198.6 μm. The average of 2 APT values determined by 2 examiners was taken as the representative APT for this patient. (B) Quantitative evaluation of vasculopathy at a postcapillary venule (PCV). Severity of luminal narrowing was determined using the ratio of luminal diameter to vessel diameter (L/V), representing the patency of the blood vessel. A PCV whose diameter was in the range 25 – 50 μm was selected for measurement. The short axis was measured, with the most severely affected vessel being chosen for the measurement. The average of 2 L/V values determined by 2 examiners was taken as the representative L/V. In this peritoneal dialysis patient (number 8), the luminal and vessel diameters were 21.5 μm and 34.8 μm respectively. Thus, the final L/V ratio was 0.62.

Figure 2

— Time course of the dialysate-to-plasma ratio of creatinine (D/P creat). (A) The D/P creat and (B) the changes from baseline in D/P creat are shown for the 11 peritoneal dialysis (PD) patients who continued PD therapy using biocompatible dialysate for more than 3 years and underwent peritoneal biopsy in the present study. (C) The D/P creat and (B) the changes from baseline in D/P creat are shown for the 99 patients who started PD therapy using biocompatible dialysate at Tokyo University Hospital between 2002 and 2009. Values are mean ± standard error of the mean. One-way repeated-measures analysis of variance and post hoc Tukey–Kramer HSD (“honestly significant difference”) test found no significant time course changes in each variable in each group.