Phosphatidylcholine and peritoneal transport during peritoneal dialysis

Peritoneal effluent of patients on chronic ambulatory peritoneal dialysis (CAPD) contains a surface-active material (SAM) made up of phospholipids and showing phosphatidylcholine on thin-layer chromatography. This substance drastically lowers surface tension, helps to repel water and has a lubricating effect. The presence of stratified phosphatidylcholine on the peritoneum might narrow the stagnant dialysate fluid layer and situations which can alter the quantity or composition of SAM may affect peritoneal transport and also, perhaps, the formation of adherences. This led us to verify, experimentally, the presence of phospholipids in basal conditions, after CAPD and during peritonitis and to check if addition of phosphatidylcholine to dialysis liquid is able to modify water transport in patients with low ultrafiltration and peritonitis. Phospholipids in the dialysis effluent of patients who have been on CAPD for a long time are lower than observed in the first days of peritoneal dialysis. A more drastic, significant decrease in phospholipids was observed in patients with low ultrafiltration and in patients with peritonitis. Mean ultrafiltration significantly increases in patients with low ultrafiltration and in those with peritonitis during dialysis exchanges containing phosphatidylcholine (50 mg/l) indicating that the latter is able to restore normal physiological conditions.     

Encapsulating peritoneal sclerosis in paediatric peritoneal dialysis patients

Encapsulating peritoneal sclerosis (EPS) is a serious complication of chronic peritoneal dialysis (CPD). In contrast to the adult population, there are few studies regarding EPS in paediatric CPD patients, and the majority of reported patients are from Japan. The aim of the present report is to define the incidence of EPS in our paediatric CPD patients and to describe the clinical and laboratory characteristics. A total of 104 paediatric patients were followed from November 1989 to November 2003 and two were diagnosed as EPS (1.9%). The dialysis periods of these patients were 45 and 53 months with 6 and 8 peritonitis episodes, respectively. Clinical signs of EPS developed 7 and 14 days after the removal of the dialysis catheter, and CPD was replaced by haemodialysis because of persistent peritonitis. One patient was well after surgical management but died 6 months later. The second patient who was treated with prednisolone remained well at 16 months. In conclusion, EPS is a rare but important complication of CPD. We recommend that all patients on CPD who develop ultrafiltration failure be evaluated radiologically for the occurrence of EPS. Management should be tailored to the individual patient.     

黄芪改善腹透患者腹腔巨噬细胞功能的临床研究

目的：研究黄芪对尿毒症患腹腔巨噬细胞功能的影响。方法：对43例尿毒症初始行腹膜透析的患在腹透液中不加（对照组）和加入黄芪注射液（用药组）治疗1周,用ELISA法检测观察前后腹腔巨噬细胞分泌TNF－a能力和吞噬功能的变化。结果：黄芪用药组腹腔巨噬细胞吞菌率、吞噬指数、杀菌率和巨噬细胞分泌TNF－a水平和对照组相比均明显上升（P＜0．01）,巨噬细胞分泌TNF－a水平与用药前自身对比也显提高（P＜0．05）。结论：腹透液中加入黄芪注射液可提高腹透患腹腔巨噬细胞功能。     

The short peritoneal equilibration test in pediatric peritoneal dialysis

The peritoneal equilibration test (PET) is the gold standard method for defining peritoneal membrane permeability and for prescribing peritoneal dialysis (PD) therapy on an individual basis. However, it is laborious, consumes nursing time, and requires many hours to be performed. Therefore, several authors have attempted to validate a short PET protocol, with controversial results. To evaluate the concordance between the 2-h (short) and 4-h (classical) peritoneal equilibrium test, a prospective observational protocol was applied in three PD centers (Mexico, Chile, and Uruguay) between July 1, 2008 and July 31 2009. PET protocol: the night prior to the test, each patient received five exchanges, 1 h each, at the same glucose concentration as previously used. Afterwards, a 2.5% glucose dialysis solution was used for a dwell time of 4 h. Exchange fill volume was 1,100 ml/m² body surface area. The next morning, the 4-h dwell was drained, and Dianeal 2.5% was infused. Three dialysate samples at 0, 2, and 4 h were obtained. A single blood sample was obtained at 120 min. Creatinine D/P and glucose D/D₀ ratios were calculated at hours 0, 2, and 4. Patients were categorized as low, low average, high average, or high transporters according creat D/P and gluc D/D₀ results. Pearson and Kappa test were used for numerical and categorical correlations, respectively, and p?<?0.05 was considered significant. Eighty-seven PET studies were evaluated in 74 patients, 33 males, age 11.1?±?5.05 years old. A positive linear correlation of 92% between 2 and 4-h creat D/P and 80% between 2 and 4-h gluc D/D₀ (p?<?0.001) was founded. The Kappa test showed a significant concordance between creat D/P and gluc D/D₀ categories at 2 and 4 h (p?<?0.001). When analyzing cut-off-value categories, creat D/P was founded to be lower and gluc D/D₀ higher than other experiences. This multicentric prospective study strongly suggests that PET obtained at 2 h and 4 h, based on either creatinine or glucose transport, provides identical characterization of peritoneal membrane transport capacity in PD children.     

Long-term peritoneal dialysis and encapsulating peritoneal sclerosis in children

Encapsulating peritoneal sclerosis (EPS) is the most serious complication of long-term peritoneal dialysis (PD), with a mortality rate that exceeds 30%. There have been many reports of the incidence of EPS being strongly correlated to the duration of PD. Patients on PD for longer than 5 years, and especially those receiving this treatment for more than 8 years, should undergo careful and repeated surveillance for risk factors associated with the development of EPS. The development of ultrafiltration failure, a high dialysate/plasma creatinine ratio, as determined by the peritoneal equilibration test, peritoneal calcification, a persistently elevated C-reactive protein level, and severe peritonitis in patients on PD for longer than 8 years are signals that should prompt the clinician to consider terminating PD as a possible means of preventing the development of EPS. The impact of the newer, biocompatible PD solutions on the incidence of EPS has not yet been determined.     

Adrenomedullin in peritoneal effluent expressed by peritoneal mesothelial cells

Background

Adrenomedullin (AM) possesses vasodilative and cell-protective properties. Glycine combines with the C-terminal of AM to form mature, physiologically active AM (mAM). AM is reportedly induced by high glucose condition in vascular endothelial or smooth muscle cells; however, little is known on how AM is activated by amidation. To investigate the behavior of AM in patients undergoing peritoneal dialysis (PD), the concentrations of AM, mAM and CA125 were measured. The mAM to AM ratio (mAM/AM ratio) was also evaluated as a marker of amidation activity.

Methods

Twenty patients were recruited for this study. The effluent at the time of the peritoneal equilibration test was collected and AM, mAM and CA125 concentrations were measured. The expression of AM in peritoneal mesothelial cells (PMCs) collected from effluent was also examined with an indirect immunofluorescent method.

Results

Mean values of AM and mAM in effluent were 18.1 ± 1.6 and 4.1 ± 0.3 fmol/mL, respectively. In plasma, they were 42.6 ± 3.3 and 5.6 ± 0.6 fmol/mL, respectively. AM concentrations in effluent did not correlate with plasma AM level but correlated well with the dialysate-to-plasma ratio of creatinine (D/P ratio of creatinine). Moreover, in 7 of 20 cases, concentrations of the mAM and mAM/AM ratio in effluent were higher than in plasma. In effluent, AM concentration but not the mAM/AM ratio correlated with CA125 concentration. Immunocytological study revealed diffuse, cytoplasmic expression of AM in PMCs which were collected from effluent during PD.

Conclusion

AM is expressed by PMCs and actively amidated in the abdominal cavity of patients undergoing PD.

     

Mitigating peritoneal membrane characteristics in modern peritoneal dialysis therapy

Membrane function at the start of peritoneal dialysis (PD) treatment, measured as solute transport rate and ultrafiltration capacity, varies considerably between individuals. Although this can be correlated to clinical factors such as age and body habitus, this accounts for little of the variance seen. It is increasingly clear, however, that this variability in membrane function does impact on clinical outcomes. Specifically, high solute transport increases mortality risk, independent of other known factors such as age, comorbidity, and residual renal function. High solute transport causes earlier loss of the osmotic gradient when a low molecular weight osmolyte such as glucose is used. This will result in an earlier and lower peak in the ultrafiltration achieved combined with a higher fluid absorption rate once the osmotic gradient is lost. It is therefore quite plausible that the worse clinical outcomes associated with high transport reflect less good ultrafiltration, although other explanations must be considered, including higher peritoneal protein losses and a possible association with systemic inflammation. Strategies now exist to mitigate the effects of high transport on fluid removal. These include optimization of the short dwell lengths using automated PD (APD) combined with icodextrin which will result in sustained ultrafiltration and thus prevention of reabsorption in the long dwell. Survival analysis of APD patients, especially in cohorts in which icodextrin has been used, would suggest that high transport status is not a risk factor, although some of these data are only preliminary. In contrast, low ultrafiltration capacity of the membrane seems to be more important in these patients, especially if anuric. Here the best strategy would seem to be prevention as patients who develop low ultrafiltration capacity are not easily treated on PD. Avoiding excessive hypertonic glucose exposure and preserving residual renal function offers the best available approach.     

Antibacterial peritoneal defence in automated peritoneal dialysis: Advantages of tidal over continuous cyclic peritoneal dialysis?

In tidal peritoneal dialysis (TPD) only a part of the infuseddialysate is drained with each exchange, leaving a residualvolume on top of which fresh fluid is cycled. As the persistentpresence of a buffered intraperitoneal reserve volume mightfavour peritoneal macrophage (PMO) function, PMO obtained fromeight patients during a 3-h continuous cyclic peritoneal dialysis(CCPD) or TPD session were studied in a randomized cross-overtrial. PMO were studied for uptake of E. coli (complement-dependent)and S. epidermidis (antibody-dependent), as well as for theirkilling capacity and peak chemiluminescence response. In addition,dialysate was sampled during both treatment sessions and studiedfor pH, osmolality, and effect on the viability of donor phagocytesand mesothelial cells. TPD-derived PMO were significantly better able to phagocytoseE. coli than CCPD-PMO (48 ±8 versus 33±6% uptake,P<0.05), whereas the other tested functional capacities revealedno significant difference between TPD- and CCPD-PMO. DuringTPD dialysate pH ranged from 6 to 7 as compared to a pH rangefrom 5 to 7 in CCPD. The presence of a residual dialysate volumeresulted in less wash-out of cells and opsonins early in thetreatment, and to some extent blunted the noxious effects offresh dialysis solutions. Overall, however, tidal PD appearedto have no advantage over CCPD regarding preservation of peritonealdefences.     

High peritoneal residual volume decreases the efficiency of peritoneal dialysis

BACKGROUND: Wide variation in peritoneal residual volume (PRV) is a common clinical observation. High PRV has been used in both continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis to minimize the time of a dry peritoneal cavity and to achieve better dialysis. However, the impact of PRV on peritoneal transport is not well established. In this study, we investigated the effect of PRV on peritoneal transport characteristics. METHODS: Peritoneal effluents were collected in 32 male Sprague-Dawley rats after a five-hour dwell with 1.36% glucose solution. Forty-eight hours later, a four hour dwell using 25 ml of 3.86% glucose solution and frequent dialysate and blood sampling was done in each rat with 125I-albumin as a volume marker. Before the infusion of the 3.86% glucose solution, 0 (control), 3, 6, or 12 ml (8 rats in each group) of autologous effluent (serving as PRV) was infused to the peritoneal cavity. RESULTS: After subtracting the PRV, the net ultrafiltration was significantly lower in the PRV groups as compared with the control group: 13.4 +/- 0.5, 12.0 +/- 1.0, 11.7 +/- 1.7, and 8.9 +/- 0.4 ml for 0, 3, 6, and 12 ml PRV groups, respectively (P < 0.001). The lower net ultrafiltration associated with higher PRV was due to (a) a significantly lower transcapillary ultrafiltration rate (Qu) caused by a lower osmotic gradient, and (b) a significantly higher peritoneal fluid absorption rate (KE) caused by an increased intraperitoneal hydrostatic pressure. No significant differences were found in the diffusive mass transport coefficient for small solutes (glucose, urea, sodium, and potassium) and total protein, although the dialysate over plasma concentration ratios values were higher in the high-PRV groups. The sodium removal was significantly lower in the PRV groups as compared with the control group (P < 0.01). CONCLUSION: Our results suggest that a high PRV may decrease net ultrafiltration through decreasing the Qu, which is caused by a decreased dialysate osmolality, and increasing the KE caused by an increased intraperitoneal hydrostatic pressure. The high volume of PRV also decreased the solute diffusion gradient and decreased peritoneal small solute clearances, particularly for sodium. Therefore, a high PRV may compromise the efficiency of dialysis with a glucose solution.     

Establishment of a novel mouse peritoneal dialysis-associated peritoneal injury model

Clinical and Experimental Nephrology - Peritoneal fibrosis induced by various factors during peritoneal dialysis (PD) can eventually lead to ultrafiltration failure and termination of PD treatment....     

Image-guided peritoneal access and management of complications in peritoneal dialysis

The principal complications of continuous ambulatory peritoneal dialysis (CAPD), namely malposition of the dialysis catheter, peritonitis, exit site infection, leakage of dialysis fluid, sclerosing peritonitis, and renal cysts and tumors, are considered in this article. The techniques that are used to reposition displaced dialysis catheters and extend the duration of dialysis are described. The role of imaging in establishing the diagnosis of peritonitis is relatively small. However, both computed tomography (CT) and ultrasound may be used to identify loculation of fluid and localized sites of sepsis, and permit percutaneous drainage. Ultrasonography of the catheter track through the percutaneous tissues allows identification of pericatheter collections in patients with exit-site infection. The technique of CT peritoneography is helpful in establishing sites of dialysis fluid leakage. These commonly occur at the site of entry of the dialysis catheter, through abdominal incisions, or along the patent tunica vaginalis into the scrotum. The appearances on CT of sclerosing peritonitis reflect pathologic changes and are characterized by the presence of peritoneal thickening and calcification. Bowel obstruction, which may develop in sclerosing peritonitis, can be identified on abdominal radiographs or barium studies of the gastrointestinal tract. Acquired renal cystic disease and renal carcinomas occur in a significant proportion of patients undergoing CAPD. Ultrasound is the investigation of first choice in the identification and clarification of the pathology (cystic or solid) of suspected renal masses.     

腹腔喷射通气对家猪腹膜氧合的影响

目的 评价腹腔喷射通气对家猪腹膜氧合的影响.方法 健康家猪24只,雌雄不拘,12～ 16周龄,体重35 ～ 45 kg,采用随机数字表法,将其随机分为3组(n=8):假手术组(S组)、腹腔常频通气组(N组)及腹腔高频通气组(H组).麻醉诱导后经口行气管插管,机械通气,于气道机械通气35 min时进行腹腔喷射通气,驱动压0.5 kg/cm2,纯氧流量1.8 L/min,吸呼比1.0:1.5,N组和H组通气频率分别为16和150次/min,腹腔通气期间每隔30 s采集动脉血样,进行血气分析,当脉搏血氧饱和度≤90％时停止腹腔通气.记录无通气安全时间(腹腔通气开始至PaO2＜ 60 mm Hg的时间).结果 与S组和N组比较,H组PaO2升高,无通气安全时间延长(P＜ 0.05),3组间PaCO2差异无统计学意义(P＞ 0.05).结论 腹腔高频喷射通气可提高家猪腹膜氧合的效果,且可延长无通气安全时间,而腹腔常频喷射通气对家猪腹膜氧合无影响.