Specific characteristics of peritoneal leucocyte populations during sterile peritonitis associated with icodextrin CAPD fluids.

BACKGROUND: Icodextrin dialysate used for peritoneal dialysis contains an iso-molar glucose polymer solution, which provides sustained ultrafiltration over long dwell times and is considered a valuable approach to reduce intraperitoneal glucose exposure. However, several side effects have been described, including abdominal pain and allergic and hypersensitivity reactions. Also, reactions compatible with chemical peritonitis have been reported. Over the period of a few months (January 2002-May 2002), a remarkable increase in the number of continuous ambulatory peritoneal dialysis (CAPD) patients using icodextrin dialysate diagnosed with sterile peritonitis was observed in our unit. METHODS: Five of the CAPD patients using icodextrin dialysate in our unit and diagnosed with sterile peritonitis were screened for leucocyte count and leucocyte differentiation during a follow-up period of 77 +/- 23 days. In addition, expression of CD14, a receptor for lipopolysaccharide (LPS), on the peripheral and peritoneal monocyte population was analysed. These results were compared to CAPD patients suffering from bacterial peritonitis. RESULTS: The peritoneal leucocyte count of CAPD patients using icodextrin dialysate and diagnosed with sterile peritonitis did not decrease significantly before treatment with icodextrin dialysate was interrupted, whereas it currently disappeared within 2-4 days in proven bacterial peritonitis. The sterile, cloudy icodextrin effluent contained an excess of macrophages on the day of diagnosis, whereas in bacterial peritonitis essentially an increase in the granulocyte population was observed. No elevation in the eosinophil population was observed. In contrast to bacterial peritonitis, we observed no increase in CD14 expression on the peripheral and peritoneal macrophages on the day of presentation and during the follow-up period. CONCLUSIONS: Specific batches of the icodextrin CAPD fluids contain a macrophage chemotactic agent, which causes a sustained inflammatory state in the peritoneal cavity. Because no increase in the expression of the LPS receptor CD14 could be observed, the increased peritoneal leucocyte count is probably not caused by LPS or LPS-like (possibly peptidoglycan-like) contamination.     

Inverse MCP-1/IL-8 ration in effluents of CAPD patients with peritonitis and in isolated cultured human peritoneal macrophages

An important event in intraperitoneal inflammation is the influx of leukocytes into the peritoneal cavity. Chemokines such as interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) play a major role in the recruitment of immune cells to the site of inflammation. We determined the concentrations of two members of the chemokine family, IL-8 and MCP-1, in the dialysate effluents of 18 continuous ambulatory peritoneal dialysis (CAPD) patients with peritonitis and of 18 non-infected CAPD patients by specific enzyme-linked immunosorbent assays (ELISA). Isolated peritoneal macrophages (PMs) from CAPD peritonitis patients were cultured and IL-8 and MCP-1 production was determined on protein (ELISA) and mRNA level (Northern blot) at designated timepoints over a 72-h culture period. PMs from non-infected patients served as controls. Much higher concentrations of IL-8 and MCP-1 were found in dialysate effluents of peritonitis patients than in effluents of non-infected patients: IL-8 2.39&plusnn;1.15 vs 0.05±0.01 ng/ml and MCP-1 release by cultured PMs from peritonitis patients and non-infected patients revealed significant differences: IL-8 40.3±2.2 ng/ml after 3 h and 194.2 ±34.9 ng/ml after 12 h compared to 21.02±6.15 ng/ml after 3 h and 89.64±30.28 ng/ml after 12 h, respectively; MCP-1 3.3±0.9 ng/ml after 3 h and 25.7±7.4 ng/ml after 12 h compared to 1.1±0.2 ng/ml and 1.8±0.2 ng/ml, respectively. Interestingly, the ratio of IL-8 to MCP-1 concentrations in the dialysate effluents (1:9.4) is reversed in the supernatants of cultured PMs. In the effluents and in the culture supernatants of PMs from CAPD peritonitis patients high amounts of IL-8 and MCP-1 are detectable, suggesting that PMs are an important source for these chemokines during peritonitis. Because of the inverse ratio of IL-8 and MCP-1 in the effluents and culture supernatants it can be assumed that PMs are responsible for the MCP-1 concentration to a lesser extent than for the IL-8 concentration in the effluents.     

Experience with renal transplantation in children undergoing peritoneal dialysis (CAPD/CCPD)

For children with end-stage renal disease, renal transplantation is the ultimate goal because it offers the potential of maximum rehabilitation. In order to evaluate the infectious risk of renal transplantation in patients previously maintained on continuous ambulatory peritoneal dialysis (CAPD) and/or continuous cycling peritoneal dialysis (CCPD), we retrospectively evalauted the clinical course of 44 pediatric patients (mean age 12.0 +/- 5.7 [SD] years) who received 32 cadaver and 16 live-related donor renal grafts after being maintained on peritoneal dialysis for 756 patient-months (mean 17.1 +/- 11.5 months). In the posttransplant period, 25 patients (57%) required dialysis because of acute tubular necrosis or acute rejection. Peritonitis developed in five patients (11%) following transplantation; two were being dialyzed at the time. Exit-site and tunnel infections occurred in nine patients (20%). In all instances, antibiotic treatment and/or catheter removal was curative. Posttransplant ascites developed in 12 patients (27%) and was alleviated by catheter drainage. The catheters were left in situ at the time of transplantation and electively removed when stable graft function was present. The 1- and 2-year actuarial graft survival rate was 65% and 55%, respectively. One patient died in the immediate posttransplant period, which was unrelated to peritoneal dialysis. In conclusion, pediatric patients maintained on CAPD and/or CCPD can be safely transplanted. The potential infectious risks related to peritoneal dialysis can be managed with appropriate management of the catheter and prompt antibiotic therapy. The patient and graft survival rates are comparable to those with patients receiving hemodialysis prior to transplantation. There is no need to limit access to transplantation in children undergoing CAPD and/or CCPD.     

Computer simulations of peritoneal fluid transport in CAPD

To model the changes in intraperitoneal dialysate volume (IPV) occurring over dwell time under various conditions in continuous ambulatory peritoneal dialysis (CAPD), we have, using a personal computer (PC), numerically integrated the phenomenological equations that describe the net ultrafiltration (UF) flow existing across the peritoneal membrane in every moment of a dwell. Computer modelling was performed according to a three-pore model of membrane selectivity as based on current concepts in capillary physiology. This model comprises small "paracellular" pores (radius approximately 47 A) and "large" pores (radius approximately 250 A), together accounting for approximately 98% of the total UF-coefficient (LpS), and also "transcellular" pores (pore radius approximately 4 to 5 A) accounting for 1.5% of LpS. Simulated curves made a good fit to IPV versus time data obtained experimentally in adult patients, using either 1.36 or 3.86% glucose dialysis solutions, under control conditions; when the peritoneal UF-coefficient was set to 0.082 ml/min/mm Hg, the glucose reflection coefficient was 0.043 and the peritoneal lymph flow was set to 0.3 ml/min. Also, theoretical predictions regarding the IPV versus time curves agreed well with the computer simulated results for perturbed values of effective peritoneal surface area, LpS, glucose permeability-surface area product (PS or "MTAC"), intraperitoneal dialysate volume and dialysate glucose concentration. Thus, increasing the peritoneal surface area caused the IPV versus time curves to peak earlier than during control, while the maximal volume ultrafiltered was not markedly affected. However, increasing the glucose PS caused both a reduction in the IPV versus time curve "peak time" and in the "peak height" of the curves. The latter pattern was also seen when the dialysate volume was reduced. It is suggested that computer modelling based on a three-pore model of membrane selectivity may be a useful tool for describing the IPV versus time relationships under various conditions in CAPD.     

Reduced peritoneal protein selectivity may indicate peritoneal fibrosis in CAPD patients

Background. We investigated peritoneal protein selectivity to evaluate whether it may indicate changes in peritoneal pores and be related to the morphological changes in the peritoneal membrane during the course of continuous ambulatory peritoneal dialysis (CAPD) therapy. Methods. Seventeen patients on CAPD (11 men, 6 women; average age, 48.4 ± 2.8 years [mean ± SE]) were studied. The duration of CAPD ranged from 1 to 42 months (21.7 ± 3.8 months [mean ± SE]). Urea nitrogen, creatinine, transferrin, and IgG in both serum and CAPD waste fluid were measured, and dialysate/plasma (D/P) ratios for these substances were determined. To evaluate changes in the large pores, in the peritoneal membrane, the peritoneal selectivity index (PSI) was calculated in the same manner as the urinary protein selectivity index is determined; namely, as the ratio of IgG clearance to transferrin clearance into CAPD waste fluid. Results. There was no significant correlation among the D/P ratios for urea nitrogen, creatinine, transferrin, IgG, and the duration of CAPD therapy. However, the PSI showed low-grade selectivity in patients on relatively shorter periods of CAPD therapy, and high-grade selectivity in patients with longer periods of CAPD therapy. There was a significant inverse correlation between the PSI (Y) and the duration of CAPD therapy (X) (Y = −0.007X + 0.75; r = 0.75, P < 0.05). We performed a prospective study after 12 months, and 8 patients were available to measure PSI again, and almost all patients showed a decrease in the PSI (−22.8 ± 0.8%; P < 0.02). In addition, we carried out morphological evaluation of the peritoneum in 13 patients who stopped CAPD. There was a significant difference in PSI value between those with and without peritoneal fibrotic change, while there was no significant difference in PSI values for those with and without mesothelial damage or with and without arteriolar sclerosis. Conclusions. From these results, we hypothesize that reduction in the PSI may reflect the shrinkage of large peritoneal pores and the presence of peritoneal fibrotic change in CAPD patients. Received: January 9, 2001 / Accepted: July 30, 2001     

Pulmonary and peritoneal tuberculosis in a CAPD patient

Patients with chronic renal failure have an increased incidence of tuberculosis due to decreased cellular immunity. More than half of the tuberculosis infection in these patients presented with extrapulmonary involvement. Tuberculous peritonitis is an important problem in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Simultaneous pulmonary and peritoneal tuberculosis is a very rare condition. We describe a 39-year-old man with culture negative CAPD peritonitis. In spite of conventional antimicrobial therapy the patient had persistent fever, weight loss, and night sweats. Approximately after one month from starting treatment, both sputum specimen and peritoneal fluid were positive for mycobacterium. Quadruple therapy for tuberculosis has been started. The response to treatment was promptly. He is still on treatment for six months and receiving CAPD. Tuberculous peritonitis should always be considered when patients on CAPD develop culture negative peritonitis treated with conventional antibiotics without improvement. In addition, the existence of extraperitoneal tuberculosis, especially pulmonary disease must be investigated.     

Effect of intraperitoneal neostigmine on peritoneal transport characteristics in CAPD.

Lymphatics have been suggested to play a major role in the absorption of dialysate, which consequently affects the adequacy of peritoneal dialysis. Neostigmine has been found to decrease lymphatic absorption in rats, presumably by causing constriction of the lymphatic stomata. We investigated the effect of neostigmine on seven continuous ambulatory peritoneal dialysis (CAPD) patients in a prospective study. We performed modified peritoneal equilibration tests both with and without intraperitoneal neostigmine in a random order. Radiolabeled albumin (0.8 mg) was added to 2 liters of dialysate +/- 2.0 mg neostigmine. We evaluated ultrafiltration and creatinine, phosphate, and urea clearances. The dialysate bag and the peritoneum were scanned at the initiation and conclusion of the four-hour dwell period. We found no change in ultrafiltration, residual volumes, creatinine, phosphate and urea clearances, or albumin recovered. Of the seven patients exposed to neostigmine, four had diarrhea, abdominal cramps, nausea, and vomiting. In conclusion, we found that 2 mg i.p. neostigmine did cause significant side-effects and did not alter transport characteristics in CAPD patients.     

Reversible peritoneal calcification in a patient treated by CAPD

The patient, a female, aged 65 years, developed diffuse peritoneal calcification nine years after commencing CAPD therapy. No abdominal symptoms or evidence of peritonitis were discovered during this period. Before peritoneal calcification was detected, a dialysate with a high glucose concentration (3.86%) had been used once daily for 16 months. In the case of this patient, it was not possible to discover any of the previous indicated etiologies of peritoneal calcification such as significantly elevated values for the product Ca x P, overt secondary hyperparathyroidism, or relapsing peritonitis. It was realized that the use of a high-glucose dialysate in a patient on long-term CAPD treatment had been one causative factor. After peritoneal calcification had been confirmed, the calcium concentration of the dialysate changed from 3.5 mEq/l to 2.5 mEq/l and the patient was put on a regime of 2.0 g alumigel (aluminum-containing phosphate binders) a day. Eight months later, a CT scan was taken. The peritoneal calcification has clearly been mitigated. At present, CAPD therapy is being continued in the absence of any abdominal symptoms.     

Plasma concentration and peritoneal clearance of oxalate in patients on continuous ambulatory peritoneal dialysis (CAPD)

Accumulation of oxalate, resulting in high plasma levels, is a common finding in end-stage renal disease. We investigated plasma concentration and peritoneal clearance of oxalate in 14 patients on continuous ambulatory peritoneal dialysis. The plasma oxalate levels in these patients (30.2 +/- 11.2 mumol/l) were as high as those in hemodialysis patients before dialysis (31.9 +/- 11.1 mumol/l). There was a significant correlation between plasma oxalate and urea nitrogen appearance (UNA). Dietary protein seems to be an important oxalate source in these patients, because the UNA reflects protein intake in stable patients. The mean peritoneal oxalate clearance was 6.64 +/- 1.56 l/day, close to the creatinine clearance. These results suggest that the plasma oxalate levels in CAPD patients may be sufficiently high to induce calcium oxalate deposition, and that methods of increasing oxalate removal and reducing oxalate burden are necessary for CAPD patients.     

Lipopolysaccharide-binding protein is present in effluents of patients with Gram-negative and Gram-positive CAPD peritonitis

Background: Bacterial peritonitis is a frequent complication during treatment of end-stage renal failure by continuous ambulatory peritoneal dialysis. Local host defence mechanisms including the secretion of proinflammatory cytokines by peritoneal macrophage are of particular importance in the pathogenesis of infectious complications. LPS-binding protein (LBP) and soluble CD14 (sCD14) are serum factors known to regulate the endotoxin-induced cellular immune response. However, it is still unknown whether LBP and sCD14 are also present in the peritoneal effluent of CAPD patients. Methods: Using specific immunoassays, we examined the concentration of LBP, sCD14 and the proinflammatory cytokines TNF=&agr;, IL-1{beta} and IL-6 in the dialysis effluents of 31 patients with CAPD-associated peritonitis. Twenty patients without peritonitis served as controls. Intraperitoneal LPS concentrations were determined using the limulus amebocyte lysate assay. Results: Bacterial lipopolysaccharide could be detected in 42% of the infected dialysis effluents. In comparison to controls (0.2±0.05 &mgr;g/ml), LBP was significantly elevated in both Gram-negative/LPS-positive (1.03±0.3 &mgr;g/ml) and Gram-positive infections (0.5±0.14 &mgr;g/ml) (P<0.05). No significant differences were detected concerning the intraperitoneal sCD14 levels in the three patient groups. Levels of TNF-&agr;, IL-1{beta} and IL-6 were significantly increased in the effluents of patients with bacterial peritonitis compared to non-infected controls. Moreover the respective cytokine concentrations were significantly higher in the Gram-negative/LPS-positive compared to the gram-positive bacterial infections (P<0.01). Conclusion: Our data demonstrate that LBP is significantly elevated in the dialysis effluents of patients with CAPD-associated peritonitis caused by both Gram-negative and Gram-positive bacteria and might be used as a marker of intraperitoneal infection. Moreover, our findings support the concept that LBP enhances the effects of LPS on cytokine production by peritoneal macrophages. The function of LBP in Gram-positive infection remains to be further elucidated. Key words: CAPD-associated peritonitis; cytokines; lipopolysaccharide-binding protein; macrophages; peritoneal dialysis; soluble CD14      

Peritonitis increases MMP-9 activity in peritoneal effluent from CAPD patients

Patients undergoing long-term continuous ambulatory peritoneal dialysis (CAPD) sometimes experience ultrafiltration failure. Mesothelial basement membrane thickening and the accumulation of submesothelial fibrotic tissue are common features of the diseased peritoneum. Peritonitis can lead to ultrafiltration failure, but the precise mechanism is not clear. The key enzymes in extracellular matrix (ECM) remodeling, namely matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), are produced by human peritoneal mesothelial cells. Using peritoneal effluent from 13 CAPD patients with peritonitis and 7 noninfected CAPD control individuals, we examined MMP and TIMP activities by gelatin and reverse zymography. Latent and activated types of MMP-2 and -9, and TIMP-1 and -2 were identified in peritoneal effluent (from all CAPD patients). Levels of latent and activated type MMP-9, as well as of TIMP-1 activities were higher at the onset of peritonitis than either during the recovery phase of peritonitis and/ or in control individuals. Activated MMP-9 activity positively correlated with leukocyte numbers and IL-6 levels in peritoneal effluent. Activities of MMP-2 and TIMP-2 in peritoneal effluent did not change between the onset of peritonitis and recovery. We concluded that increased MMP-9 and TIMP-1 levels might be associated with peritoneal ECM remodeling during peritonitis.     

Leptin in CAPD patients: serum concentrations and peritoneal loss.

BACKGROUND: To determine whether serum leptin concentrations in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) are influenced by peritoneal loss of leptin and to compare serum leptin levels of normal subjects with those of patients receiving renal replacement therapy such as haemodialysis (HD), CAPD, or kidney transplantation. SUBJECTS AND METHODS: Eighty-four individuals were investigated: six females and 14 males on standard CAPD; 13 females and 13 males on chronic HD; 10 female and eight male kidney transplant recipients, and 10 female and 10 male subjects as controls. Morning serum, 8-h and 24-h samples of peritoneal fluid concentrated to 6-20-fold by Centricon 3 (cutoff 3000 daltons), and 24-h urinary concentrations of leptin were measured with commercial RIA (Linco Research, Inc., USA). Venous blood and peritoneal fluid samples of albumin, beta2-microglobulin, glucose, urea, and creatinine were determined by standard laboratory techniques. Serum insulin levels were measured by radioimmunoassay. RESULTS: Patients (men and women) on CAPD and after kidney transplantation exhibited significantly higher serum concentrations of leptin and leptin/BMI ratios than control subjects. These increased values did not reach statistical significance in HD patients. Serum leptin concentrations were correlated very significantly with BMI in all cases (r=0.380, P<0.001). Moreover, in CAPD patients (r=0.630, P<0.007) and in HD patients (r=0.668, P<0.005), but not in kidney transplant recipients or control subjects, significant correlations were observed between serum leptin and insulin concentrations. Residual renal function (RRF) in the range 0-12.8 ml/min and serum beta2-microglobulin levels in the range 7.9-47.1 mg/l did not influence serum leptin levels in CAPD and HD patients. As expected, leptin was detected in the peritoneal fluid of CAPD patients. Twenty-four-hour peritoneal loss (30.95+/-21.05 ng/min) and 24-h peritoneal clearance (0.01+/-0.01 ml/kg/min) of leptin account for only 3.9% of estimated whole-body leptin production rate and 0.7% of leptin clearance from plasma respectively. Twenty-four-hour urinary losses of leptin in CAPD patients were negligible, accounting for 5.6+/-1.8% (range 0.3-15.2%) of total (peritoneal and urinary) loss of this hormone. CONCLUSIONS: These findings suggest that serum leptin levels are not affected by continuous peritoneal loss of leptin during CAPD and that insulin resistance and hyperinsulinaemia contribute to elevated serum leptin concentrations in CAPD and HD patients. The aetiology of increased serum leptin levels in kidney transplant recipients is probably different from that in dialysis patients.     

Computer simulations of ultrafiltration profiles for an icodextrin-based peritoneal fluid in CAPD

BACKGROUND: The three-pore model of peritoneal transport has the ability to predict ultrafiltration (UF) profiles rather accurately, even when high molecular weight (MW) solutes are employed as osmotic agents in continuous ambulatory peritoneal dialysis (CAPD). In the present simulations, we wanted to assess, for various theoretical perturbations, the UF properties of a peritoneal dialysis (PD) solution with an osmotic agent having an average MW of 20 kD and a "number average MW" of 6.2 kD, which is similar to that of icodextrin (ICO). METHODS: For a PD solution containing a completely monodispersed 20 kD MW osmotic agent, the degree of UF modeled is much higher than that reported for ICO. Hence, to model the behavior of ICO, we subdivided the ICO molecules into eight or more different MW size fractions. For simulations using six or eight subfractions, we obtained an excellent fit of simulated to reported UF data. More dispersed solutions produced UF profiles similar to that with eight fractions. RESULTS: A 2.05 L 7.5% ICO PD solution, despite being slightly hypotonic, yielded a UF volume of nearly 600 mL in 12 hours, modeled for patients not previously exposed for ICO. After nine hours, the UF volume exceeded that produced by 3.86% glucose. The UF rate and volumes increased in proportion to (1) the ICO concentration, (2) the peritoneal surface area, and (3) the peritoneal UF coefficient, but was almost insensitive to increases in the instilled fluid volume. Simulated for patients previously exposed to ICO, having steady-state plasma concentrations of ICO degradation products, the predicted UF volume at 12 hours was reduced to approximately 400 mL. CONCLUSION: Employing the three-pore model of peritoneal transport and taking into account the polydispersed nature of ICO, it was possible to accurately computer simulate the UF profiles of ICO in accordance with reported data. The simulations suggest an advantage of using ICO in patients with type I UF failure, where UF with a high-MW osmotic agent will exceed that seen in patients not showing UF failure who are on glucose-based PD solutions.     

The peritoneal transport of serum proteins and neutral dextran in CAPD patients

The peritoneal transport of five serum proteins and intravenously-administered neutral dextran was studied in 13 CAPD patients. In all patients a study was done three hours after the administration of dextran. In nine the study was repeated after 14 hours, and in six also after 38 hours. Using gel permeation chromatography of serum and dialysate it was possible to calculate fractional (relative to inulin) clearances for dextran fractions with Einstein-Stokes radii ranging from 30 to 90 A. In contrast to glomerular transport, we found that peritoneal clearances of serum proteins and corresponding dextran fractions were of a similar magnitude up to a radius of 90 A, especially in the follow-up studies. No evidence was found for a charge-selective barrier function of the peritoneum. It appeared likely that the peritoneal interstitium is probably a third compartment between blood and dialysate in which equilibrium with blood and dialysate is present for serum proteins, but initially not for dextran. For dextran this equilibrium is probably approached 14 to 38 hours after administration. The linear relationship between the reciprocal of fractional clearances and Einstein-Stokes radii indicates that restricted diffusion is the main transport mechanism of macromolecules across the peritoneal membrane. The slopes of the linear regression between the reciprocal of fractional clearances and radii ranged from 0.32 to 6.95 (slope for free diffusion 0.07) and provided an index of the permeability characteristics of the peritoneal membrane.     

Treatment of resistant CAPD peritonitis by temporary discontinuation of peritoneal dialysis

Resistant continuous ambulatory peritoneal dialysis (CAPD) peritonitis (recurrent or persistent infection) is traditionally treated by removal of the CAPD catheter and a period off peritoneal dialysis. In a pilot study we have treated 8 patients with recurrent staphylococcal peritonitis and 3 patients with persistent staphylococcal peritonitis by stopping CAPD for a 2-week period, the CAPD catheter being left in-situ. All 8 patients with recurrent peritonitis and 2 of the 3 patients with persistent peritonitis had resolution of their infection; the third patient required catheter removal to clear the infection. There were no acute problems associated with stopping CAPD, and there was no evidence of loss of peritoneal filtration capacity on restarting CAPD. This novel approach to the treatment of resistant CAPD peritonitis should reduce the number of CAPD catheters replaced and therefore diminish the risks and inconvenience to patients that such replacements entail.     

TGF-beta1 gene polymorphisms and peritoneal equilibration test results in CAPD patients

Transforming growth factor-beta1 (TGF-beta1) stimulates the expression of collagen mRNA in cultured human peritoneal mesangial cells, which may predispose them to developing peritoneal fibrosis. Polymorphisms in the signal sequence genetically may be responsible for increased TGF-beta1 production (i.e., a substitution at amino acid position 10 and 25, +869 Leu(10)-Pro and +915 Arg(25)-Pro, respectively). The aim of this study was to find out whether there is any relation between peritoneal equilibration test (PET) results and TGF-beta1 gene polymorphism. Thirty-two CAPD patients and 72 healthy subjects were included into the study. Each CAPD patient had undergone two PET with a two-year interval. The patients were classified according to the results of a baseline PET as high (high-high average) and low (low-low average) transporters. In high transporters group (n = 20), the genotype frequencies were found as 45% Leu/Leu, 55% Leu/Pro for codon 10; and 85% Arg/Arg, 15% Arg/Pro for codon 25. In low transporters group (n = 12), the genotype frequencies were detected as 66.7% Leu/Leu and 33.3% Leu/Pro for codon 10; and 83.3% Arg/Arg, 16.7% Arg/Pro for codon 25. The distribution of the TGF-beta1 genotypes in our control population was compatible with a Hardy-Weinberg equilibrium. We found no relation between TGF-beta1 genotypes and peritoneal transport group (chi(2) test, p > 0.5). There was no relation between TGF-beta1 genotype and longitudinal change in peritoneal transport. This study is the first study analyzing the possible link between TGF-betal gene polymorphisms and the characteristics of peritoneal transport and longitudinal change of peritoneal transport characteristics in CAPD patients. Further work is needed to clarify the functional importance of these two polymorphisms in TGF-beta1 production and in the development of peritoneal fibrosis.