Dialysate cyclophilin A as a predictive marker for historical peritonitis in patients undergoing peritoneal dialysis

Introduction

No markers have been used to diagnose historical peritoneal dialysis (PD)-related peritonitis. Cyclophilin A (CypA) is associated with glucose toxicity and inflammation. We hypothesize that dialysate CypA can be a marker for historical peritonitis (at least 3 months free from peritonitis).

Method

An enzyme-linked immunosorbent assay kit was used to measure the concentration of dialysate CypA. Clinical and laboratory data were collected to correlate with historical peritonitis. Mann-Whitney U test and Chi-square test were used for analysis. Receiver operating characteristic (ROC) analysis was used to evaluate predictive power.

Results

Out of a total of 31 patients who had undergone PD for at least 2 years, 18 had no history of PD-related peritonitis, while 13 had experienced PD-related peritonitis at least once. Overall, the patients in this population were in good health (normal white blood cell count, no anemia, normal electrolyte and serum albumin levels). There were no significant differences between patients with and without a history of peritonitis, except for blood white blood cell count (5650.6 ± 1848.4 vs. 7154.6 ± 2056.8, p = 0.032) and dialysate CypA value (24.27 ± 22.715 vs. 54.41 ± 45.63, p = 0.020). In the univariate analysis, only the dialysate CypA level showed a statistically significant association with historical peritonitis (HR = 1.030, 95 % CI = 1.010-1.062, p = 0.046). The AUC for dialysate CypA (>34.83 ng/mL) was 0.748, with a sensitivity of 0.615 and specificity of 0.833.

Conclusion

PD peritonitis poses a significant threat to the long-term use of peritoneal dialysis. Based on our study, even in the absence of concurrent infection, dialysate CypA can serve as a predictive marker for historical peritonitis, demonstrating high predictive power along with fair sensitivity and good specificity.

Do low GDP neutral pH solutions prevent or retard peritoneal membrane alterations in long-term peritoneal dialysis?

Several studies have been published in the last decade on the effects of low glucose degradation product (GDP) neutral pH (L-GDP/N-pH) dialysis solutions on peritoneal morphology and function during the long-term PD treatment. Compared to conventional solutions, the impact of these solutions on the morphological and functional alterations of the peritoneal membrane is discussed, including those of effluent proteins that reflect the status of peritoneal tissues. Long-term PD with conventional solutions is associated with the loss of mesothelium, submesothelial and interstitial fibrosis, vasculopathy, and deposition of advanced glycosylation end products (AGEs). L-GDP/N-pH solutions mitigate these alterations, although vasculopathy and AGE deposition are still present. Increased vascular density was found in some studies. Small solute transport increases with PD duration on conventional solutions. Initially, higher values are present on L-GDP/N-pH treatment, but these may be reversible and remain stable with PD duration. Consequently, ultrafiltration (UF) is lower initially but remains stable thereafter. At 5 years, UF and small pore fluid transport are higher, while free water transport decreased only slightly during follow-up. Cancer antigen 125 was initially higher on L-GDP/N-pH solutions, suggesting better mesothelial preservation but decreased during follow-up. Therefore, L-GDP/N-pH solutions may not prevent but reduce and retard the peritoneal alterations induced by continuous exposure to glucose-based dialysis fluids.

Non-invasive assessment of peritoneal membrane alterations

The peritoneal dialysis membrane is subject to remodelling in the course of peritoneal dialysis. In the absence of longitudinal morphological studies, this process is mainly studied indirectly by the investigation of changes in peritoneal transport. Non-invasive assessment of the peritoneum is also possible by assessment of substances that originate from peritoneal tissues and can be determined either as their gene expression in peritoneal effluent cells and/or as proteins in peritoneal effluent. Three of these biomarkers will be discussed, because longitudinal data are available. Cancer antigen 125 (CA 125) is present on the mesothelium,while its gene (MUC 16) is expressed in peritoneal effluent cells and is related to dialysate CA 125 protein. The constitutive production and the small intra-individual variability of 15% indicate its usefulness as a follow-up marker of mesothelial cell mass. Dialysate appearance rate is higher on biocompatible than on conventional solutions, but both decrease during long-term follow-up. Interleukin-6 (Il-6) is present in peritoneal effluent due to both transport from the circulation and local intraperitoneal production. Its appearance rate is unrelated to its gene expression in peritoneal cells. The intra-individual variation of effluent Il-6 averages 28%, hampering the interpretation of cross-sectional values. The relationships between effluent Il-6 and peritoneal transport have been interpreted as microinflammation, but are difficult to interprete due to mathematical coupling. Plasminogen activator inhibitor-1 (PAI-1) is encoded by the SERPINE 1 gene. A relationship is present between effluent concentration and gene expression. PAI-1 production is stimulated by glucose. PAI-1 appearance rate increases with PD duration. The sensitivity of effluent PAI-1 for the diagnosis of encapsulating peritoneal sclerosis was 100% one year prior to the diagnosis and the specificity 56%. It can be concluded that the discussed biomarkers are useful extensions to transport in assessment of the peritoneum during dialysis.  

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.

Intraperitoneal Hyaluronan Production in Stable Continuous Ambulatory Peritoneal Dialysis Patients

Objective

Several cytokines and proteins are excreted intraperitoneally during the course of peritonitis and stable states in continuous ambulatory peritoneal dialysis (CAPD) patients. Dialysate hyaluronan (HYA) is also regarded as a marker of peritoneal healing during bacterial peritonitis. We examined here, intraperitoneal HYA production in stable CAPD patients and compared the results to those of the peritoneal equilibration test (PET), the length of time on dialysis, and other marker proteins.

Design

We determined the concentration of HYA and other marker proteins in the 4-hour-dwell dialysate at 1-year intervals.

Setting

CAPD unit in Hitachi General Hospital.

Patients

The subjects were 46 stable CAPD patients who underwent 104 PETs.

Results

A correlation was found between the length of time on dialysis and the amount of HYA excretion in the 4-hr-dwell dialysate ( r = 0.403, p < 0.001). A positive but weak correlation was found between the dialysate-to-plasma ratio of the creatinine concentration and dialysate HYA excretion ( r = 0.229, p < 0.05). Seven patients were over the 90th percentile in both the concentration of HYA (>349.2 ng/mL) and the amount of HYA (>743.6 μg/4-hr dwell). Five patients exceeded 1000 μg of HYA excretion in the 4-hr-dwell dialysate, 4 of whom showed an abrupt increase of HYA excretion to more than 1000 μg/4-hr dwell, and discontinued CAPD within 6 months due to ultrafiltration failure. Two of these 4 patients were diagnosed with sclerosing encapsulating peritonitis at autopsy.

Conclusion

Intraperitoneal HYA production increased with both higher permeable membrane and the length of time on CAPD. Monitoring of HYA in the peritoneal dialysate may be useful as a marker to assess functional and morphological changes in the peritoneum in long-term CAPD patients.

Endothelial Glycocalyx and the Peritoneal Barrier

Recent advances in the study of the microcirculation have demonstrated the critical role of the endothelial glycocalyx in transcapillary transport from the plasma to the tissue interstitium. Since the capillary wall represents the initial resistance to solute transfer from the plasma through the tissue to the dialysate, the glycocalyx is potentially of major importance to peritoneal dialysis. Inadvertently removed in early histological studies, this thin, delicate layer of glycosaminoglycans and proteoglycans is now recognized as a primary barrier in transendothelial solute and water transport. Subperitoneal endothelia are exposed to inflammation, angiogenesis, and hyperglycemia, which have been shown to affect the layer by increasing permeability. This entity permits new hypotheses concerning the factors that influence the transport characteristics of peritoneal dialysis patients and provides new avenues of basic research into the fundamental mechanisms of alteration of the peritoneal barrier.

Diagnostic and prognostic role of peritoneal CA 125 in peritoneal dialysis patients presenting with acute peritonitis

BACKGROUND

Cancer antigen 125 (CA125) is made by peritoneal mesothelial cells and can be measured in spent dialysate effluent from peritoneal dialysis (PD) patients. It has been suggested that CA125 is a marker of peritoneal mesothelial cell mass and turnover. As PD CA125 increases during peritoneal inflammation, we wished to determine whether measuring PD CA125 during peritonitis provided additional information in determining outcome of peritonitis.

METHODS

We prospectively measured peritoneal CA125 in 127 adult PD patients presenting with 187 acute episodes of PD peritonitis, measuring peritoneal CA125 from a sample of dialysate effluent obtained from a 4 hour 2 litre 13.6 g/l dextrose peritoneal dwell.

RESULTS

Mean patient age 60.8 ± 17.1 years, 62.6% male, 33.7% diabetic and the median PD vintage was 22 (11-48) months. 127 patients (66.8%) presented with their first episode of peritonitis, 20% their second episode, 13.2% third or greater. Gram positive bacteria accounted for 64.7% of all peritonitis episodes and Gram negative bacteria 21.1%. Treatment was successful for 151 episodes of PD peritonitis (81.1%). The median PD effluent total WBC was 1240 (430-3660)/ml and serum CRP 67 (20-144) mg/l, with a PD CA125 of 38 (20.3-72.3) IU/l on presentation. There were positive correlations between PD effluent CA125 concentrations and total WBC on presentation (r = 0.41, p =  <0.001) and dialysis vintage (r =  -0.43, p < 0.001) but not with patient age, diabetic status, or serum CRP.There was no difference in PD effluent CA125 concentrations between Gram positive, and Gram negative peritonitis or between those episodes which responded to treatment, median 38 IU/ml (21-69) vs those with treatment failures 38 IU/ml (15-94).

CONCLUSION

We did not find any additional diagnostic or prognostic benefit for measuring effluent CA125 in PD patients presenting with acute peritonitis compared to standard investigations, including peritoneal WBC and serum CRP. As such our study would not support the routine measurement of peritoneal CA125 during episodes of peritonitis.

Dialysate cancer antigen 125 in long-term peritoneal dialysis patients

Structural and functional peritoneal membrane changes are associated with long-term peritoneal dialysis. These changes can lead to ultrafiltration failure and peritoneal fibrosis, reducing the efficacy of the peritoneal membrane to remove waste and balance fluid and electrolytes. The loss of mesothelial cells from the basement membrane is one of the major characteristics in peritoneal membrane structural change. Thus, if the reduction of peritoneal mesothelial cell mass in peritoneal dialysis patients is monitored, signs of ultrafiltration failure and peritoneal fibrosis can be detected early. One of biomarkers that can be used to indicate the change in peritoneal mesothelial cell mass is CA125, which is produced by mesothelial cells. In this article, we review the measurement and clinical use of CA125 in peritoneal dialysate effluent. Additionally, we address the data and studies on the association between dialysate CA125 levels and factors related to ultrafiltration failure and peritoneal fibrosis, including the parameters used to monitor the functional status of the peritoneal membrane. Our review shows that dialysate CA125 can be used to evaluate the peritoneal membrane in noninfected patients to predict peritoneal fibrosis, and it can also be used as a biomarker of biocompatible dialysis solutions.

Current status and practical use of effluent biomarkers in peritoneal dialysis patients

Long-term peritoneal dialysis therapy can lead to alterations in the function and morphology of the peritoneal membrane. Assessment of the peritoneal dialysis membrane usually is done by investigating the transport of small solutes and fluid. Assessment of morphologic alterations and their development would require repetitive peritoneal biopsies that usually are not feasible. Peritoneal tissues are bathed in dialysis solutions during peritoneal dialysis and may secrete or shed substances that can be recovered in peritoneal effluent. These molecular effluent biomarkers may give insight into morphologic changes. In this review, established and emerging candidate biomarkers in peritoneal dialysis are discussed. Additionally, requirements, challenges, and clinical applications of effluent biomarkers in peritoneal dialysis are addressed.

Damage of the endothelial glycocalyx in dialysis patients

Damage to the endothelial glycocalyx, which helps maintain vascular homeostasis, heightens the sensitivity of the vasculature to atherogenic stimuli. Patients with renal failure have endothelial dysfunction and increased risk for cardiovascular morbidity and mortality, but the state of the endothelial glycocalyx in these patients is unknown. Here, we used Sidestream Darkfield imaging to detect changes in glycocalyx dimension in dialysis patients and healthy controls from in vivo recordings of the sublingual microcirculation. Dialysis patients had increased perfused boundary region and perfused diameters, consistent with deeper penetration of erythrocytes into glycocalyx, indicating a loss of glycocalyx barrier properties. These patients also had higher serum levels of the glycocalyx constituents hyaluronan and syndecan-1 and increased hyaluronidase activity, suggesting the shedding of these components. Loss of residual renal function had no influence on the imaging parameters but did associate with greater shedding of hyaluronan in blood. Furthermore, patients with higher levels of inflammation had more significant damage to the glycocalyx barrier. In conclusion, these data suggest that dialysis patients have an impaired glycocalyx barrier and shed its constituents into blood, likely contributing to the sustained endothelial cell activation observed in ESRD.

Dialysate CA125 levels after 5 years on continuous peritoneal dialysis

The aim of this study was to evaluate longitudinal changes in dialysate cancer antigen 125 (dCA125) levels over time and to analyze relationships between dCA125 and peritoneal glucose exposure (PGE) in children undergoing long-term peritoneal dialysis (PD). The study group included seven boys and four girls (mean age 13 ± 5.1 years) with a mean PD duration of 84.0 ± 1.1 months. A peritoneal equilibration test (PET) was performed, and dCA125 levels were measured in all patients. Peritoneal appearance rates (AR) of dCA125, the velocity of the decrease in dCA125AR values, and annual PGE levels were also calculated. The final tests were performed at a mean of 63.3 ± 3.5 months after the initial ones. Both dCA125 and dCA125AR levels showed statistically significant decrements during the follow-up period (p = 0.003), with the velocity of decrease in dCA125AR found to be 52.6 ± 19.4%. There were no significant differences in peritoneal transport parameters between the beginning and end of the study period. PGE values were significantly higher in the last year of the study than in the first year (p = 0.014), but the velocity of the decrease in dCA125AR levels was not related to total PGE. In conclusion, a significant decline was found in dCA125 and CA125 AR levels, reflecting mesothelial cell mass, in children undergoing long-term PD (>5 years), but these were not related to PGE.

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.

Dialysate CA125 levels in children on continuous peritoneal dialysis

This prospective study was conducted to assess dialysate cancer antigen 125 (dCA125) levels in pediatric peritoneal dialysis (PD) patients and to investigate whether it exhibits any alterations during or after recovery from peritonitis, and also to analyze the relationships between dCA125 and age, duration of PD treatment, peritonitis incidence, time passed since the last episode of peritonitis, PD prescription parameters, and peritoneal transport parameters. Forty-seven standardized 4-h peritoneal equilibration tests (PET) were performed in 38 children (mean age 11.6+/-4.7 years) on PD (duration 20.9+/-14.3 months). Thirty-two of the patients were in stable condition at the time of PET (stable group). Six patients were included in the study only during a peritonitis episode, and two of the stable patients were reevaluated during a peritonitis episode afterwards (peritonitis group). Seven out of a total of eight patients with acute peritonitis were reexamined after recovery (recovery group). CA125 levels were measured in 188 samples at 0-, 1-, 2-, and 4-h dwells. Peritoneal appearance rates (AR) were calculated. Mean dCA125 (4 h) and AR CA125 values were 5.6+/-5.3 U/ml [median 4.15 U/ml/4 h (range 0.5-25.9)] and 50.1+/-45.6 U/min/1.73 m2[median 37.91 U/ml/1.73 m2 (range 3.61-223.39)]. AR CA125 levels did not correlate with age, PD duration, peritonitis incidence, time passed since the last peritonitis episode, exchange volume used per m2 per day, or peritoneal transport properties in the stable patients' group. Although stable patients using hypertonic PD solutions (n=16) had slightly lower AR CA125 levels (p=0.04), multivariate analysis showed no influence of hypertonic dextrose solutions on mesothelial CA125 secretion (p=0.4). During acute peritonitis, CA125 concentrations showed a reversible threefold increase [AR CA125: stable 37.9 vs. peritonitis 101.2 U/ml/1.73 m2 (p=0.001)]. No difference could be found between the stable group and the recovery group. We conclude that changes in the peritoneal mesothelial cell mass cannot be assessed by determining CA125 in a cross-sectional way and that longitudinal determinations could be more valuable in the follow-up of patients.

Limitations of CA125 as an index of peritoneal mesothelial cell mass

BACKGROUND

CA125 is commonly used as an index of the mesothelial cell mass in patients treated with peritoneal dialysis. However, we have no data that show a direct relationship between the number of mesothelial cells, their functional properties, and the amount of CA125 produced in these cells.

METHODS

Experiments were performed on primary in vitro cultures of human peritoneal mesothelial cells obtained from 32 donors of various ages and of both sexes. Spontaneous release of CA125 from the confluent mesothelial cells was measured and correlated with the number of cells in monolayers and with their functional properties. We also studied acute effects of cytokines (IL-1beta, TNF-alpha, and INF-gamma) and the chronic effects of glucose (45 mM) on the CA125 content in mesothelial cells and the release of this antigen from their cytosol.

RESULTS

Cells from older donors released more CA125, but we found no correlation between the number of cells and the amount of CA125 released from their cytosol. The synthesis of CA125 in mesothelial cells does not correlate with the amount of monocyte chemoattractant protein 1 or interleukin-6 produced in these cells. Acute exposure to cytokines did not modify CA125 content or its release from mesothelial cells. Chronic exposure of mesothelial cells for 4 weeks to glucose (45 mM) decreased the CA125 content of their cytosol and the release of this antigen into the culture medium. Mannitol, at the same concentration and under the same conditions, did not produce these effects, namely a decrease in the CA125 content in the cytosol or its release into the cultural medium.

CONCLUSIONS

The amount of CA125 released from mesothelial cells is not a good index of their number or their functional properties, because the CA125 release depends not only on the number of cells, but also on their properties. Furthermore, the process is affected by the age of the cell donor and environmental factors such as a high glucose content. The results of this study show the limitations of CA125 as an index of the mesothelial cell mass and viability.

Intraperitoneal cefazolin and ceftazidime effects on human peritoneal mesothelial cell release of cancer antigen-125

BACKGROUND

Intraperitoneal (IP) cefazolin and ceftazidime are recommended as empiric treatment for peritoneal dialysis (PD)-associated peritonitis. Human peritoneal mesothelial cells (HPMCs) may be affected by high IP cefazolin and ceftazidime concentrations. Peritoneal dialysate cancer antigen-125 (CA-125) appearance rate can be used to measure HPMC damage.

OBJECTIVE

To determine whether IP cefazolin and ceftazidime increase peritoneal CA-125 appearance rate.

METHODS

The study consisted of 2 phases. In phase I, no antibiotic was administered, and in phase II, patients received IP cefazolin and ceftazidime (15 mg/kg rounded to nearest 100 mg). Phase II occurred immediately after phase I. Each phase used a 4-hour dwell time with 2 L of dextrose 2.5% dialysate. Dialysate samples were collected at 0, 0.5, 1, 2, and 4 hours during each phase. Samples were assayed for CA-125, and CA-125 appearance rate was calculated.

RESULTS

Thirteen patients were recruited (7 men; aged 44.0 +/-16.0 y). The mean +/- SD (range) CA-125 dialysate concentration after phases I and II were 6.6 +/- 3.7 U/mL (2.3-15.0) and 6.4 +/-3.8 U/mL (1.6-13.8), respectively (p = 0.46). The CA-125 appearance rate after phases I and II were 51.9 +/- 31.3 U/min/1.73 m(2) (13.8-113.0) and 50.5 +/- 32.9 U/min/1.73 m(2) (11.0-104.0), respectively (p = 0.57). The slopes of the regression lines of CA-125 appearance rate were not significantly different between phases I and II.

CONCLUSIONS

These findings demonstrate that concurrently administered IP cefazolin and ceftazidime have no effect on HPMC release of CA-125 in non-infected PD patients.

Icodextrin-induced peritonitis: study of five cases and comparison with bacterial peritonitis

BACKGROUND

An epidemic of aseptic peritonitis related to the presence of peptidoglycan contaminant in some batches of icodextrin solution (Extraneal, Baxter Healthcare Corporation) occurred in Europe in the first six months of 2002.

METHODS

By case-control study we examined the clinical and biologic features of 5 patients with icodextrin-induced peritonitis (group AP) and compared them with 7 patients with bacterial peritonitis (group BP) recruited in our clinical center between January and June 2002.

RESULTS

Diagnosis of icodextrin-induced peritonitis was confirmed in all cases by a positive reintroduction test with contaminated batches of icodextrin. No recurrence was observed on re-exposure to icodextrin free of peptidoglycan. Skin tests were positive with contaminated icodextrin in 2 of 5 patients, while they were negative with icodextrin solution free of peptidoglycan (<0.6 ng/mL). During peritonitis, serum level of C-reactive protein (CRP) was lower in group AP (42.4 +/- 34 mg/L) than in group BP (135 +/- 59 mg/L) (P= 0.01). Leukocyte number in peritoneal dialysis effluent was lower in group AP (284 +/- 101/mm3), with a lower neutrophil/monocyte ratio (N/M = 0.67) than in group BP (1410 +/- 973/mm3; N/M = 4) (P < 0.05). A low number of peritoneal fluid eosinophilia (11 +/- 8%) was detected in group AP.

CONCLUSION

Icodextrin-induced peritonitis was associated with a burst of intraperitoneal cytokines. The phenotype of peritoneal neutrophils was different between aseptic and bacterial peritonitis, indicating that inflammatory stimuli that activate neutrophils in both types of peritonitis are clearly distinct. Finally, peritoneal injury measured by weight gain, peritoneal permeability, and CA125 concentration seemed to be less severe during icodextrin-induced peritonitis than during bacterial peritonitis.

Long-term clinical effects of a peritoneal dialysis fluid with less glucose degradation products

BACKGROUND

Glucose degradation products (GDPs) are cytotoxic in vitro and potentially toxic in vivo during peritoneal dialysis (PD). We are presenting the results of a two-year randomized clinical trial of a new PD fluid, produced in a two-compartment bag and designed to minimize heat-induced glucose degradation while producing a near neutral pH. The effects of the new fluid over two years of treatment on membrane transport characteristics, ultrafiltration (UF) capacity, and effluent markers of peritoneal membrane integrity were investigated and compared with those obtained during treatment with a standard solution.

DESIGN

A two-group parallel design with 80 continuous ambulatory peritoneal dialysis patients was used. The patients were randomly assigned to either the new fluid (N = 40) or to a conventional one (N = 40), and were stratified with respect to age, diabetes, and time on PD. Peritoneal transport characteristics were assessed by the Personal Dialysis Capacity (PDCtrade mark) test at 1, 6, 12, 18, and 24 months after inclusion and by weighing the overnight bag daily. Infusion pain and handling were evaluated using a questionnaire. Peritoneal mesothelial and interstitial integrity were evaluated by analyzing overnight effluent dialysate concentrations of CA 125, hyaluronan (HA), procollagen-1-C-terminal peptide (PICP), and procollagen-3-N-terminal peptide (PIIINP) at 1, 6, 12, 18, and 24 months.

RESULTS

The handling of the new two-compartment bag was considered easy, and there were no indications of increased discomfort with the new system. Furthermore, no changes in peritoneal fluid or solute transport characteristics were observed during the study period for either fluid, and neither were there any differences with regard to peritonitis incidence. However, significantly higher dialysate CA 125 (73 +/- 41 vs. 25 +/- 18 U/mL), PICP (387 +/- 163 vs. 244 +/- 81 ng/mL), and PIIINP (50 +/- 24 vs. 29 +/- 13 ng/mL) and significantly lower concentrations of HA (395 +/- 185 vs. 530 +/- 298 ng/mL) were observed in the overnight effluent during treatment with the new fluid.

CONCLUSIONS

We conclude that the new fluid with a higher pH and less GDPs is safe and easy to use and has no negative effects on either the frequency of peritonitis or peritoneal transport characteristics as compared with conventional ones. Our results indicate that the new solution causes less mesothelial and interstitial damage than conventional ones; that is, it may be considered more biocompatible than a number of conventional PD solutions currently in use.

Long-term peritoneal membrane changes

There is increasing evidence that long-term peritoneal dialysis (PD) is associated with structural changes in the peritoneal membrane. These consist of thickening of the sub-mesothelial space owing to collagen deposition and alterations in small blood vessel morphology. These alterations become more pronounced with duration of PD therapy. These changes are associated with a tendency to increasing small solute transport rate with reduced ultrafiltration. The relationship between these structural and functional changes remains unknown, but the evidence suggests that both peritonitis and exposure to dialysate contribute. The most likely components of the fluid responsible for this effect are glucose and/or its degradation products generated during heat sterilisation. Serial monitoring of peritoneal function is well established, but repeat biopsies are not practical. Effluent markers are not yet of proven value but do alter in response to a change in dialysate composition. Hopefully, a combination of reduced inflammation and more biocompatible fluids will reduce long-term changes in peritoneal membrane structure and function with a consequent improvement in patient and technique survival.

Increased production of hyaluronan by peritoneal cells and its significance in patients on CAPD

Hyaluronan (HA) is a polysaccharide that forms a critical component of extracellular matrices. HA is present in high concentrations in tissues undergoing remodeling and morphogenesis, and it appears to have an important role in the early stages of wound healing. Here, we studied the level of HA in the peritoneal dialysate effluent (PDE) from 116 stable continuous ambulatory peritoneal dialysis (CAPD) patients. Longitudinal studies over a period of 6 weeks were performed in seven of these patients who developed peritonitis. The median HA level in PDE from these patients was 154.6 microg/L (range, 29.7 to 820.2 microg/L). Dialysate level of HA increased with age of the patients, but no such correlation was shown between HA level in PDE and duration of CAPD treatment or previous episodes of peritonitis. Patients with high or average peritoneal membrane transport of small solutes had a higher HA level in the PDE than those with a low peritoneal membrane transport (P = 0.046). A significant correlation was observed between PDE level of HA and interleukin-1beta (IL-1beta) or IL-6. The plasma level of HA in these patients was significantly greater than that of healthy controls (P < 0.0001), yet the plasma concentration of HA was only 85% that of the PDE concentration. In CAPD patients with peritonitis, there was a sharp increase in the PDE levels of HA, IL-1beta, and IL-6. These values decreased progressively with resolution of peritonitis. The changes in the PDE levels of HA closely followed those of IL-1beta or IL-6. In vitro [3H]-glucosamine incorporation studies suggest that the main bulk of HA is derived from synthesis by the peritoneal mesothelial cells, whereas the amount synthesized by macrophages is trivial. We conclude that elevated levels of HA found in the PDE of stable CAPD patients originate from increased synthesis by peritoneal mesothelial cells. This event may serve as a marker of regeneration and remodeling of the peritoneal lining.

Are phospholipase A2 and nitric oxide involved in the alterations in peritoneal transport during CAPD peritonitis?

The alterations in peritoneal permeability characteristics during peritonitis can only partly be explained by the increased concentrations of prostaglandins and cytokines in the dialysate. Fifteen patients undergoing continuous ambulatory peritoneal dialysis (CAPD) with 16 peritonitis episodes were examined in the acute phase of the infection by using standard peritoneal permeability analyses (SPAs). In 9 of these patients, a control SPA could be performed. The contribution of nitric oxide (NO), prostaglandins, and the acute phase reactants C-reactive protein (CRP) and secretory phospholipase A2 (sPLA2) were analyzed. The mass transfer area coefficients (MTACs) of low-molecular-weight solutes increased during peritonitis: urea 26%, creatinine 45%, and urate 45%. The MTAC of CO2, calculated to estimate peritoneal blood flow, was 71 mL/min (34 to 254 mL/min) during peritonitis and 55 mL/min (42 to 63 mL/min) after recovery, P < or = .05. The peritoneal protein clearances were also greater during peritonitis, but this increase was not related to the molecular weight of the protein. Therefore the restriction coefficients to macromolecules were not different. The net ultrafiltration in all peritonitis episodes was lower as compared with the control dwells: -97 mL (-196 to 19 mL) versus 25 mL (-132 to 216 mL), P = .03. The prostaglandin concentrations in dialysate were greater during peritonitis than after recovery. The median increase was 199% for prostaglandin E2 (PGE2), 68% for 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), and 44% for thromboxane B2 (TxB2). Plasma sPLA2 values were 22.7 microg/L (7.3 to 407.6) during peritonitis and 8.9 microg/L (5.5 to 11.5) after recovery, P < .01. The increased plasma sPLA2 during peritonitis correlated with plasma CRP (r = .6; P = .02). The peritoneal clearances of sPLA2 were greater during peritonitis, but this could be attributed completely to the increased peritoneal transport. Both during peritonitis and after recovery, the sPLA2 clearances did not exceed the predicted values based on transport from the circulation to the dialysate. No evidence was found for local production of nitrite or nitrate. However, the MTAC of cyclic guanosine monophosphate (cGMP) was greater during the experiments performed 48 to 72 hours after the onset of peritonitis, which suggests the synthesis of NO. It can be concluded that peritonitis does not induce detectable local release of sPLA2 and that the inflammation-induced increase in the vascular surface area could not be attributed to NO in the acute phase. The activation of inducible NO synthase may occur after 48 hours.

Longitudinal follow-up of CA125 in peritoneal effluent

Mesothelial changes occur during peritoneal dialysis. CA125 provides a way to study the mesothelial cells in the in vivo situation. In the present study longitudinal changes of CA125 were analyzed. In addition, the appearance of CA125 in peritoneal effluent and day-to-day variability were studied. CA125 was measured in the effluent of five stable CAPD patients during four hour dwells with 1.36% glucose, with 3.86% glucose and with 7.5% icodextrin. In addition, CA125 was determined on six consecutive days in four hour effluents of three patients and appearance rates (AR) were calculated. Longitudinal follow-up was performed in 31 patients in whom three to seven yearly observations had been made. Linear appearance of CA125 was present in all dwells. No difference was found between the appearance rates of CA125 with 3.86% glucose, compared to either 1.36% glucose or icodextrin. Mean day-to-day coefficient of variation was 6.4% for CA125 AR, but a wide variation existed in stable CA125 values among patients (mean 22.1, range 2 to 48 U/ml). A negative trend with duration of CAPD was present in the longitudinal study. A mean decrease of 2.2% per year could be calculated, but substantial interindividual differences existed. Sudden decreases of CA125 AR were found in five patients. Possible causes were found in all of them and included a severe or recurrent peritonitis, and temporary cessation of peritoneal dialysis. In one patient a sudden decrease preceded the manifestation of peritoneal sclerosis. It can be concluded that CA125 can be used for the in vivo follow-up of the mesothelium in peritoneal dialysis patients. The appearance of CA125 in effluent is linear in time and not influenced by the initial lysis of mesothelial cells. A gradual loss of mesothelial cells is likely to occur, although interindividual variability is substantial. An acceleration of the process may be caused by severe peritonitis and perhaps by temporary cessation of peritoneal dialysis. A sudden decrease in CA125 may be an alarming sign for the development or manifestation of peritoneal sclerosis.