Distributed model of peritoneal fluid absorption

2006 ◽  
Vol 291 (4) ◽  
pp. H1862-H1874 ◽  
Author(s):  
J. Stachowska-Pietka ◽  
J. Waniewski ◽  
M. F. Flessner ◽  
B. Lindholm
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Strong Dependence ◽  
Surrounding Tissue ◽  
Distributed Model ◽  
Blood Capillary ◽  
Fluid Absorption ◽  
Blood Capillaries ◽  
Intraperitoneal Pressure ◽  
Tissue Hydration

The process of water reabsorption from the peritoneal cavity into the surrounding tissue substantially decreases the net ultrafiltration in patients on peritoneal dialysis. The goal of this study was to propose a mathematical model based on data from clinical studies and animal experiments to describe the changes in absorption rate, interstitial hydrostatic pressure, and tissue hydration caused by increased intraperitoneal pressure after the initiation of peritoneal dialysis. The model describes water transport through a deformable, porous tissue after infusion of isotonic solution into the peritoneal cavity. Blood capillary and lymphatic vessels are assumed to be uniformly distributed within the tissue. Starling's law is applied for a description of fluid transport through the capillary wall, and the transport within the interstitium is modeled by Darcy's law. Transport parameters such as interstitial fluid volume ratio, tissue hydraulic conductance, and lymphatic absorption in the tissue are dependent on local interstitial pressure. Numerical simulations show the strong dependence of fluid absorption and tissue hydration on the values of intraperitoneal pressure. Our results predict that in the steady state only ∼20–40% of the fluid that flows into the tissue from the peritoneal cavity is absorbed by the lymphatics situated in the tissue, whereas the larger (60–80%) part of the fluid is absorbed by the blood capillaries.

scholarly journals Concomitant bidirectional transport during peritoneal dialysis can be explained by a structured interstitium

2016 ◽  
Vol 310 (11) ◽  
pp. H1501-H1511 ◽  
Author(s):  
Joanna Stachowska-Pietka ◽  
Jacek Waniewski ◽  
Michael F. Flessner ◽  
Bengt Lindholm
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Phase Structure ◽  
Animal Studies ◽  
Theoretical Explanation ◽  
Distributed Model ◽  
Two Phase ◽  
Tissue Hydration ◽  
Peritoneal Tissue ◽  
Bidirectional Transport

Clinical and animal studies suggest that peritoneal absorption of fluid and protein from dialysate to peritoneal tissue, and to blood and lymph circulation, occurs concomitantly with opposite flows of fluid and protein, i.e., from blood to dialysate. However, until now a theoretical explanation of this phenomenon has been lacking. A two-phase distributed model is proposed to explain the bidirectional, concomitant transport of fluid, albumin and glucose through the peritoneal transport system (PTS) during peritoneal dialysis. The interstitium of this tissue is described as an expandable two-phase structure with phase F (water-rich, colloid-poor region) and phase C (water-poor, colloid-rich region) with fluid and solute exchange between them. A low fraction of phase F is assumed in the intact tissue, which can be significantly increased under the influence of hydrostatic pressure and tissue hydration. The capillary wall is described using the three-pore model, and the conditions in the peritoneal cavity are assumed commencing 3 min after the infusion of glucose 3.86% dialysis fluid. Computer simulations demonstrate that peritoneal absorption of fluid into the tissue, which occurs via phase F at the rate of 1.8 ml/min, increases substantially the interstitial pressure and tissue hydration in both phases close to the peritoneal cavity, whereas the glucose-induced ultrafiltration from blood occurs via phase C at the rate of 15 ml/min. The proposed model delineating the phenomenon of concomitant bidirectional transport through PTS is based on a two-phase structure of the interstitium and provides results in agreement with clinical and experimental data.

scholarly journals Role of the liver in small-solute transport during peritoneal dialysis.

1994 ◽  
Vol 5 (1) ◽  
pp. 116-120
Author(s):  
M F Flessner ◽  
R L Dedrick
Keyword(s):  
Mass Transfer ◽  
Peritoneal Dialysis ◽  
Surface Area ◽  
Peritoneal Cavity ◽  
Distributed Model ◽  
Blood Capillaries ◽  
Peritoneal Surface ◽  
Small Solute ◽  
Good Agreement

Peritoneal dialysis (PD) is dependent on the transport of water and solutes from the blood capillaries within the tissues that surround the peritoneal cavity. Because of their large blood supply and surface area, the viscera have been considered the most important tissues for PD transport. In animals, however, removal of the gastrointestinal tract decreases PD small-solute mass transfer by only 10 to 27%. To investigate the theoretical basis for these observations, a distributed model of peritoneal transport was extended to take into account the transport characteristics of four tissue groups that surround the cavity: the liver, the hollow viscera, the abdominal wall, and the diaphragm. The mass transfer-area coefficient (MTAC) of sucrose for each tissue was calculated from the following: MTAC = ([D(pa)]0.5)A, where D is the effective solute interstitial diffusivity, pa is the solute transcapillary permeability-area per unit tissue volume, and A is the apparent peritoneal surface area of the tissue. Our results for the adult human predict that the MTAC for the liver is comparable to that of all of the other viscera and makes up 43% of the total MTAC for the peritoneal cavity. The predicted MTAC is 4 cm3/min (plasma) or 6 cm3/min (blood), in good agreement with published values. It is concluded that the liver is responsible for a major portion of the small-solute MTAC. This also explains the earlier observations in eviscerated animals whose PD transport was likely preserved by intact livers.

Role of Diaphragmatic, Visceral, and Parietal Pathways in Peritoneal Fluid Absorption in Rat Peritoneal Dialysis

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 80-84 ◽  
Author(s):  
Kazuo Kumano ◽  
Kimitoshi Go ◽  
Me He ◽  
Tadasu Sakai
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Absorption Rate ◽  
Ringer Solution ◽  
Fluid Loss ◽  
Fluid Absorption ◽  
Lymphatic Absorption ◽  
Major Route ◽  
Lymphatic Pathway

Assessment was made of the contribution of lymphatic and non lymphatic fluid absorption to net fluid loss from the peritoneal cavity. Diaphragmatic, visceral, and parietal pathways in lymphatics and nonlymphatics were examined using a rat model with adhesion of the diaphragm to the liver, evisceration, these two procedures in combination, and without treatment. In each of these cases, six rats were used, each dialyzed for 180 min with Krebs–Ringer solution. The peritoneal net fluid absorption rate (PNFAR) was determined based on the disappearance of 1251-bovine serum albumin (BSA) from the peritoneal cavity and the lymphatic absorption rate (LAR), was based on the appearance of this albumin in the blood. Seventy-eight percent of net fluid loss occurred via the non lymphatic pathway, primarily through parietal and visceral absorption, and the remaining 22% through the lymphatics, the main pathway being the subdiaphragmatic lymphatics. Nonlymphatic fluid absorption would thus appear to be a major route of fluid loss from the peritoneal cavity in rat peritoneal dialysis.

Impact of Fill Volume on Peritoneal Clearances and Cytokine Appearance in Peritoneal Dialysis

2004 ◽  
Vol 24 (2) ◽  
pp. 156-162 ◽  
Author(s):  
Ramón Paniagua ◽  
María de Jesús Ventura ◽  
Ernesto Rodríguez ◽  
Juana Sil ◽  
Teresa Galindo ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Peritoneal Dialysis ◽  
Interleukin 6 ◽  
Fluid Absorption ◽  
Necrosis Factor Alpha ◽  
Intraperitoneal Pressure ◽  
Fill Volume ◽  
Dialysate Volume ◽  
Small Solute ◽  
Solute Clearance

Background Current adequacy guidelines for peritoneal dialysis encourage the use of large fill volumes for the attainment of small solute clearance targets. These guidelines have influenced clinical practice in a significant way, and adoption of higher fill volumes has become common in North America. Several studies, however, have challenged the relevance of increasing small solute clearance; this practice may result in untoward consequences in patients. Objective The present study was designed to explore the relationship between dialysate volume and the clearance of different sized molecules, fluid dynamics, and appearance of peritoneal cytokines. Methods Thirteen adult prevalent patients on continuous ambulatory peritoneal dialysis were studied. Three different dialysate volumes (2.0, 2.5, and 3.0 L) were infused on consecutive days in a random order. Several measurements of peritoneal fluid dynamics (intraperitoneal pressure, net ultrafiltration, fluid absorption), solute clearances (urea, creatinine, β2-microglobulin, albumin, IgG, and transferrin), and appearance of interleukin-6 and tumor necrosis factor alpha (TNFα) were assessed. Results Increase in dialysate fill volume (from 2 to 2.5 to 3 L) was examined in relationship to body surface area (BSA). The dialysate volume/BSA (DV/BSA) ratio increased from 1262 to 1566 to 1871 mL/m2 on 2.0, 2.5, and 3.0 L dialysate volumes, respectively. In parallel, diastolic blood pressure increased from 82.7 ± 8.8 to 87.0 ± 9.5 to 92 ± 8.3 mmHg ( p < 0.05). Net ultrafiltration rate also increased, from 0.46 ± 0.48 to 0.72 ± 0.42 to 0.97 ± 0.49 mL/minute ( p < 0.01), despite a concomitant increase in fluid absorption, from 1.05 ± 0.34 to 1.21 ± 0.40 to 1.56 ± 0.22 mL/min ( p < 0.01). Urea peritoneal clearance increased from 8.27 ± 0.68 to 9.92 ± 1.6 to 12.98 ± 4.03 mL/min ( p < 0.01); creatinine peritoneal clearance increased from 6.69 ± 1.01 to 7.64 ± 1.12 to 8.69 ± 1.76 mL/min ( p < 0.01). Clearance of the other measured molecules did not change. Appearance of interleukin-6 increased 17% and 43% ( p < 0.01), and TNFα appearance increased 14% and 50% ( p < 0.01) when dialysate volumes of 2.5 and 3.0 L were used, compared with 2.0 L. Conclusions These results show that, with higher values of DV/BSA ratio, small solute peritoneal clearance is increased, but clearances of large molecules remain unchanged. With the use of higher volumes, fluid absorption rate and the appearance of proinflammatory cytokines in the dialysate are increased.

The Importance of the Interstitium in Peritoneal Transport

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 76-79 ◽  
Author(s):  
Michael F. Flessner
Keyword(s):  
Peritoneal Dialysis ◽  
Water Transport ◽  
Peritoneal Cavity ◽  
The Body ◽  
Fluid Loss ◽  
Blood Capillary ◽  
Dialysis Fluid ◽  
Peritoneal Dialysis Fluid ◽  
Capillary Exchange ◽  
Additional Barrier

The peritoneal capillary exchange vessels are located within all the tissues which surround the peritoneal cavity and are separated from the peritoneal dialysis fluid by the tissue interstitium. The interstitium adds an additional barrier to transcapillary transport resistance and slows the diffusion of solutes from the blood to the dialysis fluid. The interstitium also alters the pressure environment of the blood capillary and has profound effects on water transport, causing fluid loss from the cavity to the body during dialysis.

scholarly journals Neutral Solution Low in Glucose Degradation Products is Associated with Less Peritoneal Fibrosis and Vascular Sclerosis in Patients Receiving Peritoneal Dialysis

2013 ◽  
Vol 33 (3) ◽  
pp. 242-251 ◽  
Author(s):  
Kunio Kawanishi ◽  
Kazuho Honda ◽  
Misao Tsukada ◽  
Hideaki Oda ◽  
Kosaku Nitta
Keyword(s):  
Peritoneal Dialysis ◽  
Quantitative Methods ◽  
Degradation Products ◽  
Blood Capillary ◽  
Neutral Solution ◽  
Peritoneal Membrane ◽  
Peritoneal Fibrosis ◽  
Neutral Group ◽  
Blood Capillaries ◽  
Glucose Degradation Products

BackgroundThe effects of novel biocompatible peritoneal dialysis (PD) solutions on human peritoneal membrane pathology have yet to be determined. Quantitative evaluation of human peritoneal biopsy specimens may reveal the effects of the new solutions on peritoneal membrane pathology.MethodsPeritoneal specimens from 24 PD patients being treated with either acidic solution containing high-glucose degradation products [GDPs ( n = 12)] or neutral solution with low GDPs ( n = 12) were investigated at the end of PD. As controls, pre-PD peritoneal specimens, obtained from 13 patients at PD catheter insertion, were also investigated. The extent of peritoneal fibrosis, vascular sclerosis, and advanced glycation end-product (AGE) accumulation were evaluated by quantitative or semi- quantitative methods. The average densities of CD31-positive vessels and podoplanin-positive lymphatic vessels were also determined.ResultsPeritoneal membrane fibrosis, vascular sclerosis, and AGE accumulation were significantly suppressed in the neutral group compared with the acidic group. The neutral group also showed lower peritoneal equilibration test scores and preserved ultrafiltration volume. The density of blood capillaries, but not of lymphatic capillaries, was significantly increased in the neutral group compared with the acidic and pre-PD groups.ConclusionsNeutral solutions with low GDPs are associated with less peritoneal membrane fibrosis and vascular sclerosis through suppression of AGE accumulation. However, contrary to expectation, blood capillary density was increased in the neutral group. The altered contents of the new PD solutions modified peritoneal membrane morphology and function in patients undergoing PD.

Computer simulations of osmotic ultrafiltration and small-solute transport in peritoneal dialysis: a spatially distributed approach

2012 ◽  
Vol 302 (10) ◽  
pp. F1331-F1341 ◽  
Author(s):  
Joanna Stachowska-Pietka ◽  
Jacek Waniewski ◽  
Michael F. Flessner ◽  
Bengt Lindholm
Keyword(s):  
Peritoneal Dialysis ◽  
Computer Simulations ◽  
Peritoneal Cavity ◽  
Sodium Concentration ◽  
Solute Concentration ◽  
Distributed Model ◽  
Peritoneal Surface ◽  
Distributed Approach ◽  
Peritoneal Tissue ◽  
Spatially Distributed

The aim of this study was to simulate clinically observed intraperitoneal kinetics of dialysis fluid volume and solute concentrations during peritoneal dialysis. We were also interested in analyzing relationships between processes in the peritoneal cavity and processes occurring in the peritoneal tissue and microcirculation. A spatially distributed model was formulated for the combined description of volume and solute mass balances in the peritoneal cavity and flows across the interstitium and the capillary wall. Tissue local parameters were assumed dependent on the interstitial hydration and vasodilatation induced by glucose. The model was fitted to the average volume and solute concentration profiles from dwell studies in 40 clinically stable patients on chronic ambulatory peritoneal dialysis using a 3.86% glucose dialysis solution. The model was able to describe the clinical data with high accuracy. An increase in the local interstitial pressure and tissue hydration within the distance of 2.5 mm from the peritoneal surface of the tissue was observed. The penetration of glucose into the tissue and removal of urea, creatinine, and sodium from the tissue were restricted to a layer located within 2 mm from the peritoneal surface. The initial decline of sodium concentration (sodium dip) was observed not only in intraperitoneal fluid but also in the tissue. The distributed model can provide a precise description of the relationship between changes in the peritoneal tissue and intraperitoneal dialysate volume and solute concentration kinetics. Computer simulations suggest that only a thin layer of the tissue within 2–3 mm from the peritoneal surface participates in the exchange of fluid and small solutes between the intraperitoneal dialysate and blood.

scholarly journals Solute Transport Across the Peritoneal Membrane

2002 ◽  
Vol 13 (suppl 1) ◽  
pp. S84-S91
Author(s):  
John K. Leypoldt
Keyword(s):  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Peritoneal Cavity ◽  
Molecular Size ◽  
Fluid Absorption ◽  
Peritoneal Membrane ◽  
Dialysis Dose ◽  
Transport Pathways ◽  
Stage Renal Disease ◽  
End Stage

ABSTRACT. The current understanding of the transport pathways that govern solute removal during peritoneal dialysis is reviewed. Diffusive transport rates across the peritoneal membrane for small solutes are slow. Even though the rate of diffusive solute transport decreases with increasing molecular size, large molecules (e.g., albumin) are nevertheless removed from the patient during routine peritoneal dialysis. Recent work has confirmed a previous suggestion that diffusive solute transport is limited by the small area of the peritoneal membrane that participates in the transport process. This small functional area is due to either poor contact of the peritoneal membrane with dialysis solution bathing the peritoneal cavity or to the limited surface area of capillaries that perfuse peritoneal tissues. Convective solute transport during peritoneal dialysis is proportional to the transperitoneal ultrafiltration rate but is less than that expected, because of low solute sieving by the peritoneal membrane and fluid absorption from the peritoneal cavity. Low solute sieving across the peritoneal membrane was first identified in 1966, a phenomenon that is now attributed to the presence of water-only transport pathways mediated by aquaporin-1. Fluid absorption from the peritoneal cavity occurs at the same time as transperitoneal ultrafiltration, but the pathways by which these two processes occur simultaneously remain speculative. This review proposes a novel hypothesis, whereby fluid absorption occurs in areas of the peritoneal membrane that are governed by different physical forces than those governing transperitoneal ultrafiltration. Further understanding of the pathways for fluid and solute transport during peritoneal dialysis will permit improvements in the adequacy of the dialysis dose and the more efficacious use of peritoneal dialysis to treat patients with end-stage renal disease.

Exchange of macromolecules between peritoneal cavity and plasma

1985 ◽  
Vol 248 (1) ◽  
pp. H15-H25 ◽  
Author(s):  
M. F. Flessner ◽  
R. L. Dedrick ◽  
J. S. Schultz
Keyword(s):  
Molecular Weight ◽  
Peritoneal Cavity ◽  
Intraperitoneal Injection ◽  
Transport Coefficients ◽  
Fluorescein Isothiocyanate ◽  
Ringer Solution ◽  
Blood Capillary ◽  
Dialysis Fluid ◽  
Sprague Dawley ◽  
Blood Capillaries

The exchange of fluorescein isothiocyanate-labeled dextrans ranging in weight-averaged molecular weight from 19,400 to 160,000 and 125I-bovine serum albumin (BSA) between dialysis fluid (5% BSA in Krebs-Ringer solution) in the peritoneal cavity and the plasma was studied in anesthetized female Sprague-Dawley rats. Plasma and peritoneal samples were collected for 3-4 h after either 1) an intraperitoneal injection of dialysis fluid with tracer or 2) an intravenous injection of tracer material simultaneously with an intraperitoneal injection of dialysis solution without tracer. Analysis of the data by means of a mathematical model of the transport process suggests a functional asymmetry in transport of large molecules across the blood capillary wall. Substances injected intravenously have a net transport from the blood capillaries to the peritoneal cavity. Substances of molecular weight greater than or equal to 39,000 transport from the cavity to the plasma via peritoneal lymphatics; 19,400 molecular-weight dextran transports from the cavity to the plasma primarily via lymphatics with some blood capillary uptake. Tissue diffusivities and capillary mass transport coefficients are derived for the substances tested.

scholarly journals Imaging and leaks in peritoneal dialysis

2021 ◽  
Vol 4 (2) ◽  
pp. 77-84
Author(s):  
Simon Duquennoy ◽  
Vincent Leduc ◽  
Emilie Podevin
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Surgical Intervention ◽  
Individual Risk ◽  
Intraperitoneal Pressure ◽  
Non Invasive ◽  
Clinical Events ◽  
Leakage Site ◽  
Magnetic Resonance Imaging Mri ◽  
Individual Risk Factors

Dialysate leaks are non-rare mechanical but dreaded complications in peritoneal dialysis (PD). They usually occur at the beginning of PD, with various clinical events depending on their location. Use of imaging tests such as computed tomography (CT) peritoneography, or magnetic resonance imaging (MRI) peritoneography, or scintigraphic peritoneography, can confirm the diagnosis and guide surgical intervention if needed. These simple, non-invasive, and accessible tests can be done in collaboration between the radiological et peritoneal teams. Depending on the leakage site, PD can be pursued with small volumes with a cycler. In other cases, it must be interrupted and the patient transferred to hemodialysis, in order to permit the peritoneal cavity to regain its integrity by cicatrization or with surgical intervention. Imaging can help to make sure peritoneal cavity has regained its integrity after this period of transition. Early leaks can be avoided by delaying PD start with by 14 days. Intraperitoneal pressure does not seem to contribute significantly. Prevention of PD leaks essentially depends on individual risk factors such as obesity or anterior abdominal surgeries. This article reviews the characteristics of dialysate leaks in PD and the imagery tests to limit transfer to hemodialysis.

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