Multicenter laparoscopic evaluation of the peritoneum in peritoneal dialysis patients

Laparoscopic findings have been used to confirm peritoneal degenerations in peritoneal dialysis (PD) therapy. This study evaluated morphological changes in the peritoneum and their clinical relevance in patients undergoing PD. Laparoscopic findings at the rectovesical peritoneum were evaluated and scored using an imaging system at the time of PD catheter removal in this multicenter study. Angiogenesis evaluated by the vascular score (VS), color changes score (CCS), plaque score (PS), PD duration, history of peritonitis, dialysate/plasma creatinine (D/P Cr) levels, and age at PD termination were statistically analyzed. The VS of patients with PD duration more than 96 months was significantly decreased compared with that of the other patients and was negatively correlated with D/P Cr levels at PD termination. The CCS for patients with PD duration more than 96 months were significantly higher than those for the other patients and positively correlated with D/P Cr levels at PD termination. The PS of patients with recurring peritonitis were significantly higher than those of the other patients. Diminished vascularity and increased color changes in the peritoneum may be predictive of D/P Cr levels with peritoneal degradation. Laparoscopic evaluation of the abdominal cavity can provide detailed information about peritoneal injury.

Mesothelial Paracrystalline Inclusions in Continuous Ambulatory Peritoneal Dialysis Patients

♦ Objective

Uremia is known to be followed by changes in the serous membranes of pleura, pericardium, and peritoneum. During continuous ambulatory peritoneal dialysis (CAPD), the peritoneum is exposed to altered body conditions as well as to the influence of dialysate. The aim of the present study was to examine the ultrastructure of the mesothelial cells in CAPD patients, and to compare the findings with those from studies of the peritoneum in uremic controls. Paracrystalline intracytoplasmic inclusions in mesothelial cells were objects of special interest.

♦ Methods

Biopsies of human parietal peritoneum were studied. These were taken from 12 uremic patients during catheter implantation before the start of CAPD, and from 7 CAPD patients during catheter removal for infection or malfunction. The samples were prepared in the standard way to be studied by transmission electron microscopy (TEM).

♦ Results

Paracrystalline intracytoplasmic inclusions were seen in mesothelial cells only by TEM. They appear as filamentous structures at the outer part of the inclusions, and as pearl-like structures at the core of the inclusions. Sacculate dilatations of rough endoplasmic reticulum cisternae with partly destroyed membranes and only few ribosomes were also seen, with and without densely osmiophilic filaments within the cisternae. We have found paracrystalline intracytoplasmic inclusions in mesothelial cells from uremic and CAPD patients both. According to the literature, these changes are present in one third of biopsies from uremic patients. Until now, however, they have not been mentioned in CAPD patients.

Vascular and Interstitial Changes in the Peritoneum of Capd Patients with Peritoneal Sclerosis

Objective

To analyze morphological changes in the peritoneum of peritoneal sclerosis (PS) patients. Emphasis was put on vascular abnormalities, because the continuous exposure to glucose-based dialysis solutions could cause diabetiform changes and because longitudinal transport studies suggested the development of a large peritoneal vascular surface area.

Design

Peritoneal biopsies from continuous ambulatory peritoneal dialysis (CAPD) patients were investigated in two studies. Diabetic patients were excluded. In study 1, 11 PS biopsies were compared to three control groups varying in duration of CAPD treatment: 0 months ( n = 15), 2 – 25 months ( n = 7), and > 25 months CAPD ( n = 7). The second study was a case-control study, comparing six biopsies from the long-term control group to six PS biopsies, matched for age and duration of CAPD. All biopsies were scored for presence and type of fibrosis [Picro Sirius red, type IV collagen, α-smooth muscle actin (αSMA)] and for neoangiogenesis (factor VIII). Thickening of vascular walls by type IV collagen and vasodilation of capillaries were measured by computer-aided planimetry.

Results

In study 1 the presence of sclerosing fibrosis, deposition of interstitial type IV collagen, and the number of myofibroblasts (αSMA-positive cells) was greater in the PS biopsies than biopsies from all control groups ( p < 0.002). Moreover, the number of vessels per field was higher in PS biopsies ( p < 0.01). Vascular wall thickening of small arteries ( p < 0.008) and vasodilation of capillaries were found in PS biopsies compared to all control groups ( p < 0.007). The second study revealed differences in the presence of sclerosis but not in the extent of fibrosis between PS biopsies and their controls. The number of vessels per field in PS biopsies was higher compared to controls ( p = 0.04). Also, thickening of the vascular wall was more marked in PS biopsies ( p = 0.03). Vasodilation of capillaries was greater in PS biopsies than in controls ( p = 0.07).

Conclusion

Fibrosis of the peritoneum may precede peritoneal sclerosis. The deposition of type IV collagen and the presence of myofibroblasts in the interstitial layer could be part of a pathologic process similar to the scarring in diabetic nephropathy. Neoangiogenesis and thickening of the vascular wall by type IV collagen are consistent with glucose-induced microangiopathy. These abnormalities and the vasodilation of the capillaries can explain the high dialysate-to-plasma ratios or mass transfer area coefficients of low molecular weight solutes that can be found in long-term CAPD patients.

The Plasma Leak–to–Response Hypothesis: A Working Hypothesis on the Pathogenesis of Encapsulating Peritoneal Sclerosis after Long-Term Peritoneal Dialysis Treatment

Encapsulating peritoneal sclerosis (EPS) is one of the most serious complications of long-term peritoneal dialysis (PD). Long-term PD therapy has been suggested as a risk factor for EPS development among patients in Japan and Australia. Although the primary mechanism of EPS development has not been clarified, histologic changes of the peritoneum associated with prolonged PD are postulated to be causally related. The present article proposes a working hypothesis—the plasma leak–to–response hypothesis—that vascular alterations in the peritoneum of long-term PD patients play a crucial role in the initiation and development of EPS.

The Choice of Dialysis Solutions in Pediatric Chronic Peritoneal Dialysis: Guidelines by AnAD HOCEuropean Committee

Objective

To provide guidelines on choosing dialysis solutions for children on chronic peritoneal dialysis (PD).

Setting

European Paediatric Peritoneal Dialysis Working Group.

Data Source

Literature on the application of PD solutions in children ( Evidence), and discussions within the group ( Opinion).

Conclusions

Glucose is the standard osmotic agent for PD in children ( Evidence). The lowest glucose concentration needed should be used ( Opinion). Low calcium solution (1.25 mmol/L) should be applied, wherever possible, with careful monitoring of parathyroid hormone levels ( Opinion). The use of amino acid-containing dialysis fluids can be considered in malnourished children, although aggressive enteral nutrition is preferred ( Opinion). There is insufficient evidence documenting the efficacy of intraperitoneally administered amino acids ( Evidence). When ultrafiltration and/or solute removal are insufficient, poly-glucose solutions are a welcome addition to the treatment of children on nocturnal intermittent PD ( Evidence). However, in the absence of any reported long-term experience with children, their use must be closely monitored ( Opinion). Bicarbonate would appear to be the preferred buffer for PD in children, but more in vivo studies are required before it replaces the present lactate-containing solutions ( Evidence/Opinion).

Biocompatibility of Peritoneal Dialysis Fluids: Long-term Exposure of Nonuremic Rats

Objectives

Long-term peritoneal dialysis (PD) leads to structural and functional changes in the peritoneum. The aim of the present study was to investigate the long-term effects of PD fluid components, glucose and glucose degradation products (GDP), and lactate-buffered solution on morphology and transport characteristics in a nonuremic rat model.

Methods

Rats were subjected to two daily intraperitoneal injections (20 mL/day) during 12 weeks of one of the following: commercial PD fluid (Gambrosol, 4%; Gambro AB, Lund, Sweden), commercial PD fluid with low GDP levels (Gambrosol trio, 4%; Gambro AB), sterile-filtered PD fluid (4%) without GDP, or a glucose-free lactate-buffered PD fluid. Punctured and untreated controls were used. Following exposure, the rats underwent a single 4-hour PD dwell (30 mL, 4% glucose) to determine peritoneal function. Additionally, submesothelial tissue thickness, percentage of high mesothelial cells (perpendicular diameter > 2 μm), vascular density, vascular endothelial growth factor (VEGF), and transforming growth factor (TGF) β1mRNA expression were determined. Submesothelial collagen concentration was estimated by van Gieson staining.

Results

Submesothelial tissue thickness and vascular density, mediated by VEGF and TGFβ production, in the diaphragmatic peritoneum increased significantly in rats exposed to any PD fluid. Gambrosol induced a marked increased fibrosis of the hepatic peritoneum. A significant increase in high mesothelial cells was observed in the Gambrosol group only. Net ultrafiltration was reduced in the Gambrosol and in the glucose-free groups compared to untreated controls. Small solute transport was unchanged, but all groups exposed to fluids showed significantly increased lymph flow.

Conclusions

Our results show that long-term exposure to different components of PD fluids leads to mesothelial cell damage, submesothelial fibrosis, and neoangiogenesis. Mesothelial cell damage could be connected to the presence of GDP; the other changes were similar for all fluids. Peritoneal transport characteristics did not change in any consistent way and the neoangiogenesis observed was not paralleled by increased solute transport.

What Can We Do to Preserve the Peritoneum?

Background

Long-term peritoneal dialysis may lead to peritoneal membrane failure. Loss of ultrafiltration is the most important clinical abnormality. Loss of ultrafiltration is associated with an increased number of peritoneal blood vessels, with fibrotic alterations, and with loss of mesothelium. Continuous exposure to bioincompatible dialysis solutions is likely to be important in the pathogenesis of these alterations.

Methods

This article reviews the toxicity of various constituents of dialysate, current assessments of interventions, and the results of interventions aimed at preserving the peritoneum.

Results

Glucose, possibly in combination with lactate, and glucose degradation products (GDPs) are likely to be the most toxic constituents of dialysate. Diabetiform peritoneal neoangiogenesis is likely to be mediated by vascular endothelial growth factor (VEGF). Release of VEGF might be influenced by glucose-induced cellular pseudohypoxia, which is likely to be increased by exposure to lactate. Glucose and GDPs are both toxic to peritoneal cells. Glucose degradation products induce the formation of advanced glycosylation end-products at a much faster rate than does glucose itself, but the relative importance of GDPs and glucose in clinical PD has not been clarified. The effects of interventions should first be assessed in long-term animal models, followed by clinical studies on peritoneal transport and on effluent markers that may reflect the status of the peritoneum. Possible interventions aim at reducing peritoneal exposure to glucose, GDPs, and lactate. Techniques include peritoneal resting, replacing some glucose-based exchanges with amino acid–based and icodextrin-based dialysate, using bicarbonate as a buffer, and administering solutions that have a low GDP content. Exposure to various dialysis solutions with a reduced GDP content has resulted in an increase in the effluent concentration of the mesothelial cell marker CA125, irrespective of the buffer used. Experimental studies in a long-term peritoneal exposure model in rats showed that the combination of a reduction in the concentration of lactate and replacement of lactate with pyruvate resulted in a reduction of the number of peritoneal blood vessels. Results of drug therapy have been studied in various animal models. Their use in patients is still experimental.

Conclusions

Strategies to preserve the peritoneum aim at reducing membrane exposure to bioincompatible solutions. Currently available dialysis fluids that are more biocompatible are likely to have some beneficial effects. Further research on the development of dialysis solutions that use combinations of osmotic agents and alternative buffers is necessary.

Peritoneal Dialysis

These presentations highlighted some of the current research needs in peritoneal dialysis. They are not meant to eclipse other important issues, such as adequacy and nutrition. These needs have become apparent as the therapy has evolved and progressed. They in fact are a testament to the increasing acceptance, use, and development of the therapy and suggest that there is potential for even further advancement for the therapy of peritoneal dialysis in the future.

Alterations in Water and Solute Transport with Time on Peritoneal Dialysis

Peritoneal ultrafiltration capacity and small -solute transport characteristics seem to be relatively stable in most patients treated with PD for up to 3 years. However, in patients treated with PD for 4 years or more, there is a tendency towards increasing diffusive transport for small solutes as well as a tendency towards decreasing net UF, whereas the peritoneal protein clearances seem to be reduced or stable.

Loss of UFC is a well-known complication during long-term PD treatment, and the risk for loss of UFC may be as high as 50% after 6 years on PD. Several different mechanisms of UFC loss have been reported. In particular, the most common mechanism for loss of UFC is increased diffusive transport resulting in rapid glucose absorption and thus rapid loss of the osmotic driving force. Also reported as causes of UFC loss have been: reduced efficiency of the osmotic agent (perhaps owing to decreased transcellular water transport); loss of peritoneal surface area with slow solute transport owing to fibrosis and the formation of adhesions (during the late stage of sclerosing peritonitis); and increased peritoneal fluid absorption. In individual patients, a combination of several mechanisms may be involved in the apparent UFC failure.

The Biology of the Mesothelium during Peritoneal Dialysis

Substantial derangements of mesothelial biology are observed during experimental simulations of dialysis conditions, inferred from the content of human dialysis effluent and visualized by microscopy of human mesothelial biopsies. Canosmotically active solutions be made biocompatible with the osmoregulatory system of the mesothelium? Can the contributions of the mesothelium to host defenses against inflammation and/or infection be supported during CAPD? Do underlying metabolic derangements present in various kidney diseases and end-stage renal disease, regardless of cause, require customized CAPD protocols and solutions? Use of dialysis solutions less directly toxic to the mesothelium is a necessary step toward some day manipulating peritoneal biology by pharmacological and therapeutic modalities.

Dialysate Cancer Antigen 125 Concentration as Marker of Peritoneal Membrane Status in Patients Treated with Chronic Peritoneal Dialysis

Objective

This study reviews publications on the history of cancer antigen 125 (CA125), the background of its use as a marker of mesothelial cell mass, determination in peritoneal effluent, and its practical use in both the follow-up of peritoneal dialysis (PD) patients and as a marker of in vivo biocompatibility of dialysis solutions.

Design

Review article.

Results

CA125 is a high molecular weight glycoprotein. Previous studies in ascites suggested its release by mesothelial cells. In vitro studies with cultured mesothelial cells showed constitutive production, the majority of which was dependent on mesothelial cell mass. Serum CA125 is normal in PD patients, but its concentration in peritoneal dialysate suggests local release, probably from mesothelial cells. Effluent CA125 can be considered a marker of mesothelial cell mass in stable PD patients, but large amounts are found during peritonitis, due probably to necrosis of mesothelial cells. The majority of studies found no relationship between dialysate CA125 and peritoneal transport parameters. Some cross-sectional studies reported a relationship with duration of PD, but others were unable to confirm this, due probably to the large interindividual variability. Longitudinal follow-up has shown a decrease in dialysate CA125, indicating loss of mesothelial cell mass. Application of theoretically morebiocompatible PD solutions causes an increase in dialysate CA125.

Conclusions

Dialysate CA125 is a mesothelial cell mass marker. The concentration of CA125 should be determined after a standardized dwell. A single low value is not informative. A decrease with time on PD suggests loss of mesothelial cell mass. Dialysate CA125 is a marker of in vivo biocompatibility of (new) dialysis solutions. More research is necessary on the best methodology for measuring low concentrations and establishing normal values and a significant change.

Biocompatibility of a Peritoneal Dialysis Solution with Amino Acids: Histological Evaluation in the Rabbit

Objective

To determine the biocompatibility of a peritoneal dialysis (PD) solution containing amino acids compared to PD solutions containing glucose.

Design

The biocompatibility of three dialysis solutions containing 1.1% amino acids, 1.36% glucose, and 3.86% glucose, respectively, was evaluated in vivo in rabbits.

Methods

After 60 days of PD, peritoneal histological changes in rabbits were investigated by light and transmission electron microscopy. The parameters investigated were: (1) mesothelial damage; (2) submesothelial edema; (3) submesothelial cell infiltration; (4) submesothelial fibrosis; and (5) vascular alterations. Semiquantitative evaluations were performed for all the above alterations; quantitative morphometric evaluation was performed for mesothelial damage (cubic transformation of the mesothelium, areas devoid of mesothelium, submesothelial edema) and thickness of peritoneal arteriole walls.

Results

(1) Mesothelial damage was practically nonexistent in rabbits dialyzed with the solution containing amino acids, and intermediate and severe with low glucose and high-glucose solutions, respectively. Both controls and rabbits dialyzed with amino acid solution showed flat continuous mesothelium; rabbits dialyzed with low-glucose solution showed cubic continuous mesothelium; and rabbits dialyzed with high-glucose solution showed cubic discontinuous mesothelium. Cytopathic mesothelial effects were slight with the solution containing amino acids and severe with both the low and high-glucose solutions. Duplication and thickening of mesothelial basement membrane were never observed. (2) Submesothelial edema showed a worsening trend from controls to rabbits dialyzed with solution containing amino acids, low glucose, and high glucose. (3) No difference in submesothelial infiltration was found between groups. (4) Submesothelial fibrosis was never observed. (5) Vascular alterations were never observed.

Conclusion

These results are evidence that PD solution with amino acids is more biocompatible than high and also low-glucose solutions.

Taking Peritoneal Dialysis beyond the Year 2000

Over the past 25 years, peritoneal dialysis (PD) has steadily improved so that now its outcomes, in the form of patient survival, are equivalent to, and at times better than, those for hemodialysis. We now have a better understanding of the pathophysiology of peritoneal membrane function and damage and the importance of appropriate prescription to meet agreed-upon targets of solute and fluid removal. In the next millennium, greater emphasis will be put on prescription setting and subsequent monitoring. This will entail an increase in automated PD, especially for lifestyle reasons as well as for patients with a hyperpermeable peritoneal membrane.

To improve outcomes, dialysis should be started earlier than is currently the case. It is easy to do this with PD, where an incremental approach is made easier by the introduction of icodextrin for long-dwell PD. In the future, solutions will be tailored to be more biocompatible and to provide improved nutrition and better cardiovascular outcomes.

Finally, economic considerations favor PD, which is cheaper than in-centre hemodialysis. Thus, for many, PD has become a first-choice therapy, and with further improvements this trend will continue.

Does the Biocompatibility of the Peritoneal Dialysis Solution Matter in Assessment of Peritoneal Function?

Background

Peritoneal function tests are performed in peritoneal dialysis (PD) patients to characterize peritoneal membrane status. A low pH/high glucose degradation product (GDP) dialysis solution is used as the test solution. The objective of the present study was to compare a 3.86% glucose, low pH/high GDP dialysis solution (pH 5.5) with a 3.86% glucose, normal pH/low GDP dialysis solution (pH 7.4) in assessments of peritoneal membrane function.

Methods

Two standard peritoneal permeability analyses (SPA) were performed in 10 stable PD patients within 2 weeks. One SPA was done with the 3.86% low pH/high GDP solution, and the other with the 3.86% normal pH/low GDP solution. The sequence of the two tests was randomized.

Results

Fluid transport parameters and glucose absorption were not different between the two groups. No differences were found for the mass transfer area coefficients (MTACs) of low molecular weight solutes calculated over the whole dwell. However, MTAC urea in the first hour of the dwell was higher in the test done with low pH/high GDP dialysate, suggesting more peritoneal vasodilation. No difference was found in protein clearances. Sodium sieving at multiple time points during the dwell was similar with the two solutions.

Conclusion

The results obtained with the glucose-containing normal pH/low GDP dialysis solution were similar to those obtained with the glucose-containing low pH/high GDP dialysate in assessments of peritoneal membrane function.

The plasma pharmacokinetics of fosfomycin and metronidazole after intraperitoneal administration in patients undergoing appendectomy for uncomplicated appendicitis

We aimed to investigate the pharmacokinetics of fosfomycin and metronidazole after intraperitoneal administration of the combination of fosfomycin and metronidazole in patients undergoing laparoscopic appendectomy for uncomplicated appendicitis. We included eight otherwise healthy men undergoing laparoscopic appendectomy. The trial treatment was administered at the end of the surgical procedure and left in the abdominal cavity. Trial drugs consisted of 4 g fosfomycin and 1 g metronidazole in a total volume of 500.2 mL. Blood samples were collected prior to and ½, 1, 2, 4, 8, 12 and 24 h after administration. High-performance liquid chromatography-mass spectrometry was used for the measurement of plasma concentrations, and pharmacokinetic calculations were undertaken. Antimicrobial susceptibility testing was undertaken on isolates from intraoperatively collected specimens. The median maximal concentration for fosfomycin in plasma was 104.4 mg/L, median time point for the maximal concentration was 1.5 h, median half-life 3.0 h, and median area under the curve 608 mg*h/L. The median maximal concentration for metronidazole in plasma was 13.6 mg/L, median time point for the maximal concentration was 2.0 h, median half-life 7.3 h, and median area under the curve was 164 mg*h/L. All aerobic bacteria were susceptible to fosfomycin, and all anaerobes were susceptible to metronidazole. Plasma concentrations of fosfomycin and metronidazole were in line with concentrations reported from pharmacokinetic studies after intravenous administration and were within therapeutic ranges.

Intracellular Glutathione in Human Peritoneal Mesothelial Cells Exposed in vitro to Dialysis Fluid

Effect of peritoneal dialysis fluids on glutathione (GSH/GSSG) level in human peritoneal mesothelial cells was tested in in vitro experiments. To mimic in vivo conditions, cells were initially exposed to dialysis fluids (Dianeal 1.36%, Dianeal 2.27%, Dianeal 3.86%) that subsequently were diluted with dialysate effluent at time intervals. GSH/GSSG concentration in cells initially decreased but returned to normal values thereafter. This decrease in the intracellular concentration of glutathione was less when pH of the tested dialysis fluid was adjusted to 7.3. In further experiments with mesothelial cells exposed to Earle's salts solution supplemented with glucose and/or lactate, we have shown that in the presence of low pH, lactate is the main factor causing depletion of intracellular glutathione. When added to the dialysis solution at a concentration of 0.1 mM, L-2-oxothiazolidine-4-carboxylate, a precursor of glutathione, not only prevents the initial decrease in glutathione concentration but also augments the final intracellular level of this thiol.

Peritoneal Dialysis Fluid-Induced Fragmentation of Golgi Apparatus as a Biocompatibility Marker

In vitro biocompatibility assessments that consider physiologically appropriate conditions of cell exposure to peritoneal dialysis fluids (PDFs) are still awaited. In this study, we found that fragmentation of Golgi apparatus occurred in a pH-dependent manner within 30-min exposure to five distinct commercially available PDFs, which showed no marked difference in their effects on cell viability in the conventional MTT assay. Fluorescence microscopy analysis of labeling antibody against cis-Golgi protein GM130 indicated that the stacked cisternal structure was maintained in the perinuclear area of both M199 culture medium and a neutral-pH PDF groups. However, this specific structure became partially disassembled over time even in a neutral-pH PDF, and fragmentation was markedly enhanced in cells exposed to neutralized-pH PDFs in correspondence with their intracellular pH; moreover, in acidic PDFs, Golgi staining was diffuse and scattered in the entire cytoplasm and showed partial aggregation. The Golgi fragmentation markedly observed with the neutralized PDFs could be reversed by replacing either the media with a neutral-pH medium or a mixture of PDF and PD effluent (PDF) in a gradient manner mimicking clinical conditions. Furthermore, although weaker than pH effect, notable effects of other PDF-related factors were also observed after 30-min exposure to pH-adjusted PDFs. Lastly, the results of studies conducted using MAPK/SAPK inhibitors indicated that the mechanism underlying the Golgi fragmentation described here differs from that associated with the fragmentation that occurs at the G2/M checkpoint in the cell cycle. We conclude that Golgi fragmentation is suitable for rapid biocompatibility assessment of PDF not only because of its strong pH dependence but also because the fragmentation is recognizably affected by PDF constituents.

State of the Art on Autologous Mesothelial Transplant in Animals and Humans

Sixteen years ago rabbit and human mesothelial cells were successsfully cultured and autoimplanted. The aim of the study was merely to demostrate that mesothelial implant was possible and interesting not only in peritoneal dialysis, but also in the vaster field of medicine and surgery concerning all the mesothelial districts of the body.

The aim of this paper is to recollect the steps which have led to autolougous mesothelial transplantation and verify if the tecnique has been validated and adopted by others.

Review of the literature published in the last 15 years shows that intraperitoneal transplantation of mesothelial cells has been effective in reducing the formation of peritoneal adhesions, and in remodeling the area of mesothelial denudation. New studies on the mesothelial cell opened the way to costruction of transplantable tissue-engineered artificial peritoneum, to the utilization of mesothelial progenitor cells and to find simple metods to collect autologous mesothelial cells.

Finally mesothelial trasnsplantation may represent a new neovascular therapy in the prevention and treatment of ischemic coronaric heart disease.

Encapsulating Peritoneal Sclerosis

Encapsulating peritoneal sclerosis (EPS) is a rare but serious complication of peritoneal dialysis. In this review, we describe the clinical picture and histologic changes to the peritoneal membrane that are associated with EPS and provide an update on current diagnosis and management. We also discuss the recent studies that have suggested that the use of more biocompatible solutions containing lower concentrations of glucose degradation product that often are pH neutral in combination with a change in clinical practice (reducing glucose exposure and monitoring peritoneal membrane function) might ameliorate peritoneal degeneration, reduce the incidence of EPS, and minimize the severity of the disease.

A new peritoneal dialysis fluid for Japanese patients: a randomized non-inferiority clinical trial of safety and efficacy

BACKGROUND

We report here two new peritoneal dialysis fluids (PDFs) for Japan [BLR 250, BLR 350 (Baxter Limited, Japan)]. The PDFs use two-chamber systems, and have bicarbonate and lactate buffer to a total of 35 mmol/L. In separate trials, the new PDFs were compared to two "standard" systems [PD-4, PD-2 (Baxter Limited, Japan)]. The trials aimed to demonstrate non-inferiority of peritoneal creatinine clearance (pCcr), peritoneal urea clearance (pCurea) and ultrafiltration volume (UF), and compare acid-base and electrolyte balance.

METHODS

We performed randomized, multicenter, parallel group, controlled, open-label clinical trials in stable continuous ambulatory peritoneal dialysis (CAPD) patients. The primary endpoints were pCcr and UF. The secondary endpoints were serum bicarbonate and peritoneal urea clearance. The active phase was 8 weeks. These trials were performed as non-inferiority studies, with the lower limit of non-inferiority for pCcr and UF set at 3.2 L/week/1.73 m² and 0.12 L/day, respectively.

RESULTS

108 patients (28 centers) and 103 patients (29 centers) took part in the two trials. Groups were well balanced at baseline. The investigative PDFs were non-inferior to the "standard" ones in terms of primary endpoints, comparable in terms of pCurea, and superior in terms acid-base balance, especially correcting those with over-alkalinization at baseline.

CONCLUSIONS

We demonstrated fundamental functionality of two new PDFs and showed superior acid-base balance. Given the propensity of Japanese CAPD patients for alkalosis, it is important to avoid metabolic alkalosis which is associated with increased cardiovascular mortality risk and accelerated vascular calcification. The new PDFs are important progress of CAPD treatment for Japanese patients.

Multidisciplinary clinical strategies for encapsulating peritoneal sclerosis in peritoneal dialysis: update from Japan

Peritoneal dialysis is established as a first-line standard renal replacement therapy for end-stage renal disease. However, the development of encapsulating peritoneal sclerosis has been a critical complication among long-term peritoneal dialysis patients. During the past decade, multidisciplinary approaches have been used to suppress encapsulating peritoneal sclerosis. The present article reviews the historical and present status of encapsulating peritoneal sclerosis in Japan.

Encapsulating peritoneal sclerosis in the era of a multi-disciplinary approach based on biocompatible solutions: the NEXT-PD study

INTRODUCTION

Encapsulating peritoneal sclerosis (EPS) is a serious complication of peritoneal dialysis (PD). Over the past decade in Japan, a multidisciplinary approach has been adopted to minimize the incidence and improve outcomes of EPS. This strategy includes planned PD discontinuation for high-risk patients and the introduction of biocompatible solutions. This study examined the current clinical status of EPS in representative PD centers in Japan.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Patients (n = 1,338) from 55 PD centers in Japan who were using neutral-pH solutions from the initiation of therapy (mean age, 62 years; median PD duration, 32 months; concomitant use of icodextrin, 35.2%; PD and hemodialysis combination therapy, 12.2%) were assessed every 6 months to ascertain the reasons for PD discontinuation and the development of EPS development. Outcomes were also recorded. The study period was from November 2008 to March 2012.

RESULTS

There were 727 patients who discontinued PD, including 163 deaths. Among all causes of PD withdrawal except for death, planned PD discontinuation to avoid EPS was utilized in 58 cases (7.1% in total). The strategy was increasingly utilized in proportion to the duration of PD: 0.5% for patients undergoing PD for < 3 years, 0.6% for patients undergoing PD for 5 years, 14.7% for patients undergoing PD for 8 years, and 35.5% for patients undergoing PD for > 8 years. Fourteen patients developed EPS (three cases after PD), which corresponded with an overall incidence of 1.0%. The incidence according to the duration of PD was 0.3% for PD < 3 years, 0.6% for PD = 5 years, 2.3% for PD = 8 years, and 1.2% for PD > 8 years. In terms of therapy, 11 patients were treated with prednisolone (PSL), and surgical enterolysis was utilized in two cases. Complete remission of abdominal symptoms was achieved in twelve patients (85.7%), and three died due to EPS (mortality rate of 21.4%).

CONCLUSIONS

Use of the multidisciplinary approach described above reduces the risk of the development of EPS according to PD duration. In cases of de novo EPS cases in Japan, this strategy can also attenuate the clinical course of the condition.

Peritoneal dialysis: from bench to bedside

Peritoneal dialysis was first employed in patients with acute renal failure in the 1940s and since the 1960s for those with end-stage renal disease. Its popularity increased enormously after the introduction of continuous ambulatory peritoneal dialysis in the end of 1970s. This stimulated both clinical and basic research. In an ideal situation, this should lead to cross-fertilization between the two. The present review describes two examples of interactions: one where it worked out very well and another where basic science missed the link with clinical findings. Those on fluid transport are examples of how old physiological findings on absorption of saline and glucose solutions were adopted in peritoneal dialysis by the use of glucose as an osmotic agent. The mechanism behind this in patients was first solved mathematically by the assumption of ultrasmall intracellular pores allowing water transport only. At the same time, basic science discovered the water channel aquaporin-1 (AQP-1), and a few years later, studies in transgenic mice confirmed that AQP-1 was the ultrasmall pore. In clinical medicine, this led to its assessment in patients and the notion of its impairment. Drugs for treatment have been developed. Research on biocompatibility is not a success story. Basic science has focussed on dialysis solutions with a low pH and lactate, and effects of glucose degradation products, although the first is irrelevant in patients and effects of continuous exposure to high glucose concentrations were largely neglected. Industry believed the bench more than the bedside, resulting in 'biocompatible' dialysis solutions. These solutions have some beneficial effects, but are evidently not the final answer.

Peritoneal dialysis in veterinary medicine

Peritoneal dialysis is a modality of renal replacement therapy that is commonly used in human medicine for treatment of chronic kidney disease and end-stage kidney failure. Peritoneal dialysis uses the peritoneum as a membrane across which fluids and uremic solutes are exchanged. In this process, dialysate is instilled into the peritoneal cavity and, through the process of diffusion and osmosis, water, toxins, electrolytes, and other small molecules, are allowed to equilibrate.

Monitoring of the peritoneal membrane

Background. Indirect methods can be used to provide valuable information about peritoneal structure and function for the indirect analysis of peritoneal membrane. Methods. The focus of this paper will be on the commonly available tools for this purpose. First, the value and clinical relevance of CA125 as a marker of mesothelial cell mass in peritoneal effluent will be evaluated. Thereafter, monitoring the peritoneal membrane by using its properties to transport solutes and water will be discussed. Results. The data obtained can be useful for tailoring dialysis adequacy, analysis of clinical problems such as ultrafiltration failure or to predict the development of peritoneal sclerosis.

Impact of new dialysis solutions on peritonitis rates

Peritonitis remains a major cause of morbidity among patients on peritoneal dialysis (PD), yet there is little information about the effect of new biocompatible dialysis solutions on peritonitis rates and treatment. In our unit, information on each peritonitis episode is prospectively collected. Since 2003, bicarbonate/lactate dialysate has been gradually introduced for new patients and for patients experiencing abdominal pain with conventional lactate solutions. From 2002 to 2005, data from 121 episodes of peritonitis (71 automated PD and 50 continuous ambulatory PD) were analyzed; 107 episodes occurred in patients using standard lactate dialysate and 14 episodes in patients using bicarbonate/lactate solution. Patients using bicarbonate/lactate had a significantly lower peritonitis rate of 1 per 52.5 patient-months compared to those using standard lactate dialysate (1 per 26.9 patient-months) (P=0.0179). Response to treatment, however, was not affected by the type of dialysate; cure rates (71.4 and 69.1%, respectively) and recurrence rates (21.4 and 15.8%, respectively) were not significantly different. Catheter removal was required in three (21.4%) patients using bicarbonate/lactate and 23 (22.4%) patients using lactate solution. Use of biocompatible dialysate appears to reduce the peritonitis rate by 50%, although this has to be confirmed in a randomized study. The type of dialysate, on the other hand, does not affect response to treatment.

Prevention of membrane damage in patient on peritoneal dialysis with new peritoneal dialysis solutions

Peritoneal dialysis (PD) is now an established and successful alternative to hemodialysis. Multiple studies have confirmed its equivalent dialysis adequacy, mortality and fluid balance status, at least for the first 4-5 years. Peritoneal membrane failure is now one of the leading cause of technique failure. This review describes the role of glucose, glucose degradation product, pH, lactate, advanced glycosylation end product (AGE) in causing this membrane damage, and gives insight how the use of newer peritoneal dialysis fluids (PDFs) containing icodextrin, amino acids and bicarbonate buffer can prevent peritoneal membrane damage.

Histological and functional characteristics of peritoneal membrane in peritoneal sclerosis of PD patients

BACKGROUND

Function and structure of peritoneal membrane (PM) are impaired on peritoneal dialysis (PD). Peritoneal sclerosis is a common finding in peritoneal biopsies (PB) of PD patients. The aim of this study was to examine the impact of peritoneal sclerosis on peritoneal function and clinical parameters in PD patients submitted to peritoneal biopsy.

METHODS

A PB was performed on 31 PD patients during catheter removal due to malfunction or after drop-out from treatment. For each patient PM transport was evaluated by the last peritoneal equilibration test before PB. Each daily glucose load was calculated. Tissue was formalin-embedded and stained for histological and immunohistochemical studies.

RESULTS

Patients with submesothelial sclerosis and those with impairment of submesothelial basement membrane and subendothelial vascular membrane were submitted to a larger daily glucose load. Peritoneal sclerosis > 50 microns was more frequent in high transporters, who were exposed to larger daily glucose load compared to medium-high transporters. Mesothelial loss is correlated to peritoneal sclerosis and vascular injuries.

CONCLUSIONS

Peritoneal sclerosis is not constant in PD patients: it is related to the loss of mesothelium integrity, to the daily glucose load of PD treatment and to vascular injuries, but apparently not to the presence of inflammatory infiltrate. It remains a matter of debate how much the peritoneal sclerosis modifies the function of PM and how new more biocompatible PD solutions could reduce PM injury.

Peritoneal Dialysis: A Viable Renal Replacement Therapy Option

The number of patients with end-stage renal disease requiring dialysis has increased markedly over the last decade and continues to grow at an alarming rate in the United States. Of the currently available dialysis options for end-stage renal disease (hemodialysis and peritoneal dialysis), peritoneal dialysis (PD) is underutilized in the United States for nonmedical reasons. In fact, PD is the less expensive dialysis modality and may provide a survival advantage over hemodialysis in first 2 to 4 years of treatment, but that advantage is not as robust with increasing age and with the presence of diabetes. Moreover, the initial survival advantage is lost in long-term PD, mainly owing to changes in the peritoneal membrane from the use of conventional bio-incompatible PD solutions. Current data suggest that not many patients continue on PD beyond 10 years. The recent development of a more biocompatible PD solution should help to preserve membrane function, promote ultrafiltration, improve nutritional status, and, it is hoped, prolong the survival advantage of PD. Identification of molecular mechanisms involved in cellular responses leading to peritoneal fibrosis and angiogenesis evokes new therapeutic strategies that might protect the peritoneal membrane against the consequences of long-term PD.

Short- and Medium-Term Increase of CA125 in Peritoneal Effluent using a Neutral-pH Solution

♦ Objective

To investigate the effects of an alternative peritoneal dialysis (PD) solution composed of a lactate/bicarbonate (Lac/Bic) mixture (35/2 mmol/L), pH 7.0, on the appearance of cancer antigen 125 (CA125) in the peritoneal effluent.

♦ Methods

Eight stable PD patients received a conventional solution containing 35 mmol/L lactate (Lac) for 11.9 ± 9.2 months, and then changed to Lac/Bic for 3.1 ± 0.7 months. Each patient acted as his/her own control.

♦ Results

We studied 4 males and 4 females with a mean age of 57.4 ± 16.8 years. Higher concentrations (U/mL) ( p < 0.005) and appearance rates (AR) (U/min) ( p < 0.05) of CA125 in the dialysate were observed with Lac/Bic than with Lac, during the sampling times of the peritoneal equilibration test (10, 120, and 240 minutes) and in the overnight effluent: CA125 5.7 versus 0.6, 18.9 versus 1.9, 29.7 versus 3.7, and 43.2 versus 5.5 U/mL; and AR 1177 versus 125, 354 versus 36,297 versus 37, and 194 versus 26 U/min, respectively. Mean CA125 content in the 24-hour dialysate was 34.2 U/min (baseline) and 30.9 U/min (11.9 months) with Lac, and 207.9 U/min and 185 U/min after 1.6 and 3.1 months with Lac/Bic ( p = 0.009). The intraperitoneal pH was more physiological during the dwell with the Lac/Bic solution.

♦ Conclusions

The CA125 levels in the peritoneal effluent with Lac/Bic are an effect of the solution's neutral pH, as other factors of the prescription were constant. The Lac/Bic solution is more biocompatible than Lac, reflecting short- and medium-term changes in the mesothelial cells, whose clinical significance has not yet been determined.