The new peritoneal dialysis solutions: friends only, or foes in part?

Current techniques in peritoneal dialysis

OBJECTIVE

To provide a current overview of the technique of peritoneal dialysis in dogs and cats.

CLINICAL IMPLICATION

Peritoneal dialysis is the process by which water and solutes move between blood in the peritoneal capillaries and fluid (dialysate) instilled into the peritoneal cavity, across the semipermeable membrane of the peritoneum. The primary indication for peritoneal dialysis (PD) in animals is for treatment of renal failure to correct water, solute, and acid-base abnormalities and to remove uremic toxins.

SUMMARY

Peritoneal dialysis is a modality of renal replacement therapy commonly used in human medicine for the treatment of chronic kidney disease and end-stage kidney failure. Peritoneal dialysis utilizes the peritoneum as a membrane across which fluids and uremic solutes are exchanged. 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.

NFAT5 contributes to osmolality-induced MCP-1 expression in mesothelial cells

Increased expression of the C-C chemokine monocyte chemoattractant protein-1 (MCP-1) in mesothelial cells in response to high glucose concentrations and/or high osmolality plays a crucial role in the development of peritoneal fibrosis during continuous ambulatory peritoneal dialysis (CAPD). Recent studies suggest that in kidney cells osmolality-induced MCP-1 upregulation is mediated by the osmosensitive transcription factor, nuclear factor of activated T cells 5 (NFAT5). The present study addressed the question of whether activation of NFAT5 by hyperosmolality, as present in PD fluids, contributes to MCP-1 expression in the mesothelial cell line Met5A. Hyperosmolality, induced by addition of glucose, NaCl, or mannitol to the growth medium, increased NFAT5 activity and stimulated MCP-1 expression in Met5A cells. siRNA-mediated knockdown of NFAT5 attenuated osmolality-induced MCP-1 upregulation substantially. Hyperosmolality also induced activation of nuclear factor-κB (NF-κB). Accordingly, pharmacological inhibition of NF-κB significantly decreased osmolality-induced MCP-1 expression. Taken together, these results indicate that high osmolalities activate the transcription factor NFAT5 in mesothelial cells. NFAT5 in turn upregulates MCP-1, likely in combination with NF-κB, and thus may participate in the development of peritoneal fibrosis during CAPD.

The role of leptin and its short-form receptor in inflammation in db/db mice infused with peritoneal dialysis fluid

BACKGROUND

In peritoneal dialysis (PD), the peritoneal membrane exhibits structural and functional changes following continuous exposure to the non-physiological peritoneal dialysis fluid (PDF). In this study, we examined the effect of PDF on peritoneal adipose tissue in a diabetic milieu.

METHODS

Six-week-old db/db mice and their non-diabetic littermates (db/m) were subjected to uninephrectomy. All animals then received intra-abdominal infusion of lactated Ringer's solution (Ringer) or 1.5% glucose-containing PDF (Dianeal) twice daily. Mice were sacrificed 4 weeks later. Parietal and visceral adipose tissues were harvested for examining gene and protein expression of adiponectin, leptin, monocyte chemotactic protein-1, vascular endothelial growth factor, tumor necrosis factor alpha (TNF-α), transforming growth factor beta and interleukin 6 (IL-6). Expression of TNF-α and F4/80+ macrophage accumulation in adipose tissues was assessed by immunohistochemical staining. Modulation of leptin synthesis and leptin receptors expression and the relevant signaling pathways were also determined by quantitative reverse transcription-polymerase chain reaction, immunoblotting or enzyme-linked immunosorbent assay.

RESULTS

Compared to Ringer infusion, Dianeal infusion significantly increased serum leptin but decreased adiponectin in db/db mice. Increased expression of leptin, TNF-α and IL-6 was observed in visceral but not in parietal adipose tissue. Dianeal infusion also increased F4/80+ macrophage accumulation and enhanced the expression of pro-inflammatory cytokines including IL-6 and TNF-α in the visceral adipose tissue. Compared to db/m mice, infusion with Dianeal exhibited a more deleterious effect on db/db mice, characterized by an upregulation of short-form leptin receptor ObRa and activation of the mitogen-activated protein kinase signaling pathway.

CONCLUSION

In conclusion, PD-induced hyperleptinemia amplifies the inflammatory response of adipose tissue through short-form leptin receptor when the long-form isotype is defective.

Risk Factors Associated with Encapsulating Peritoneal Sclerosis in Dutch Eps Study

Objective

Encapsulating peritoneal sclerosis (EPS) is a serious complication of peritoneal dialysis (PD) with a multifactorial pathophysiology and possible increasing incidence. The aim of the present study was to evaluate the independent associations of PD duration, age, dialysis fluids, and kidney transplantation with EPS.

Methods

A multicenter case–control study was performed in the Netherlands from 1 January 1996 until 1 July 2007. The population comprised 63 patients with EPS and 126 control patients. Control patients were selected from the national registry and were matched for date of PD start. Associations were analyzed using a log linear regression model. Primary outcome was appearance of EPS.

Results

Compared with control patients, patients with EPS were younger at the start of PD (34.7 ± 15.4 years vs. 51.5 ± 14.7 years, p < 0.0001). The cumulative period on PD was longer in EPS patients than in control patients (78.7 ± 37.8 months vs. 32.8 ± 24 months, p < 0.0001), and the cumulative period on icodextrin was also longer in EPS patients (32.7 ± 23.3 months vs. 18.1 ± 15.7 months, p = 0.006). Compared with control patients, more EPS patients underwent kidney transplantation (47 vs. 59, p < 0.0001). With regard to the period after transplantation, the yearly probability of EPS increased in the year after transplantation to 7.5% from 1.75%. In multivariate regression analysis, cumulative PD duration, age at PD start, transplantation, time from last transplantation to EPS, calendar time, time on icodextrin, and ultrafiltration failure were independently associated with EPS. Transfer from PD to hemodialysis for reasons other than suspected EPS could not be identified as a risk factor for EPS.

Conclusions

Duration of PD, age at PD start, kidney transplantation, time since last transplantation, ultrafiltration failure, and time on icodextrin were associated with a higher risk of EPS.

Insulin resistance and lower plasma adiponectin increase malignancy risk in nondiabetic continuous ambulatory peritoneal dialysis patients

End-stage renal disease patients have a higher risk for developing cancer. Although several causes for this increased risk have been proposed, the risk factors for cancer development in this population have not been elucidated. The aim of this study was to determine whether metabolic derangements, including insulin resistance and altered adipokines, increase the risk of developing malignancies in peritoneal dialysis (PD) patients, who are vulnerable to metabolic disorders because of excessive glucose absorbed from the dialysate. Study subjects comprised 106 nondiabetic PD patients who had been on PD for a minimum of 3 months with no overt malignancy. Baseline anthropometry, fasting glucose, insulin, and adiponectin were measured. The development of malignancy was evaluated during the follow-up period. During the mean follow-up of 47.0 ± 23.7 months, malignancy occurred in 15 patients (14.2%). The most common site of cancer was the kidney (26.7%), followed by thyroid (13.3%) and stomach (13.3%). Baseline insulin levels and homeostasis model assessment of insulin resistance were significantly higher, whereas plasma adiponectin levels were significantly lower, in patients who developed malignancy. Cox proportional hazards analysis revealed that insulin levels, homeostasis model assessment of insulin resistance, and lower adiponectin were independent predictors of malignancy. These findings demonstrate that insulin resistance and lower adiponectin levels could be risk factors for malignancy in nondiabetic PD patients.

Rapid Solute Transport in the Peritoneum: Physiologic and Clinical Consequences

This review focuses on the physiologic and clinical consequences of rapid solute transport in the peritoneum. The concept, the current understanding of related factors, and the possible causes implicated in rapid solute transport are discussed first. Then, the consequences, with particular emphasis on mortality, are highlighted. Finally, based on recent advances and clinical studies, some strategies for the treatment of fast peritoneal transport are reviewed.

Peritoneal Defense Mechanisms—the Effects of New Peritoneal Dialysis Solutions

It remains to be determined whether the peritoneal dialysis procedure induces abnormalities in the normal host defenses of the abdominal cavity and whether these perturbations are important in the pathogenesis of peritonitis. The peritoneum is a smooth membrane that lines the abdominal cavity and participates in the diffusion of water and solutes during peritoneal dialysis. The diaphragmatic lymphatic uptake and the opsonization of micro-organisms, with phagocytosis and killing by peritoneal macrophages, mesothelial cells, lymphocytes, polymorphonuclear leukocytes, and newly defined proteins such as defensins, play a combined role in the peritoneal host defense. Because the composition of earlier peritoneal dialysis fluids is clearly non-physiologic, continuous exposure of peritoneal cells to these solutions may result in an impairment of the local peritoneal host defense mechanisms. However, with the newer solutions, it has been shown that peritoneal defense mechanisms may improve.

Peritoneal dialysis prescription in children: bedside principles for optimal practice

There is no unique optimal peritoneal dialysis prescription for all children, although the goals of ultrafiltration and blood purification are universal. In turn, a better understanding of the physiology of the peritoneal membrane, as a dynamic dialysis membrane with an exchange surface area recruitment capacity and unique permeability characteristics, results in the transition from an empirical prescription process based on clinical experience alone to the potential for a personalized prescription with individually adapted fill volumes and dwell times. In all cases, the prescribed exchange fill volume should be scaled for body surface area (ml/m(2)), and volume enhancement should be conducted based on clinical tolerance and intraperitoneal pressure measurements (IPP; cmH(2)O). The exchange dwell times should be determined individually and adapted to the needs of the patient, with particular attention to phosphate clearance and ultrafiltration capacity. The evolution of residual kidney function and the availability of new, more physiologic, peritoneal dialysis fluids (PDFs) also influence the prescription process. An understanding of all of these principles is integral to the provision of clinically optimal PD.

Biocompatibility of a bicarbonate-buffered amino-acid-based solution for peritoneal dialysis

Amino-acid-based peritoneal dialysis (PD) fluids have been developed to improve the nutritional status of PD patients. As they may potentially exacerbate acidosis, an amino-acid-containing solution buffered with bicarbonate (Aminobic) has been proposed to effectively maintain acid-base balance. The aim of this study was to evaluate the mesothelial biocompatibility profile of this solution in comparison with a conventional low-glucose-based fluid. Omentum-derived human peritoneal mesothelial cells (HPMC) were preexposed to test PD solutions for up to 120 min, then allowed to recover in control medium for 24 h, and assessed for heat-shock response, viability, and basal and stimulated cytokine [interleukin (IL)-6] and prostaglandin (PGE(2)) release. Acute exposure of HPMC to conventional low-glucose-based PD solution resulted in a time-dependent increase in heat-shock protein (HSP-72) expression, impaired viability, and reduced ability to release IL-6 in response to stimulation. In contrast, in cells treated with Aminobic, the expression of HSP-72 was significantly lower, and viability and cytokine-producing capacity were preserved and did not differ from those seen in control cells. In addition, exposure to Aminobic increased basal release of IL-6 and PGE(2). These data point to a favorable biocompatibility profile of the amino-acid-based bicarbonate-buffered PD solution toward HPMC.

Peritoneal membrane structural and functional changes during peritoneal dialysis

Peritoneal dialysis is now utilized as a renal replacement therapy modality in a substantial percentage of patients with end-stage renal disease, with excellent short-term patient and technique survival rates. However, the potential complications associated with longer-term therapy, such as ultrafiltration failure or encapsulating peritoneal sclerosis, have led to raise some concern about peritoneal dialysis as an adequate mode of treatment of end-stage renal disease in the long term. In the last decade, a substantial amount of information has been gathered on the characteristics of the peritoneal membrane at the onset of peritoneal dialysis, and on the anatomical and pathophysiologic changes that occur with long-term peritoneal dialysis. I will review this subject with a special focus on the various strategies that can help protect the peritoneal membrane during peritoneal dialysis so as to allow peritoneal dialysis to succeed as a long-term dialysis modality.