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.

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.

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.

Mass Transfer Area Coefficients in Children

1994 ◽  
Vol 14 (1) ◽  
pp. 30-33 ◽  
Author(s):  
Denis F. Geary ◽  
Elizabeth A. Harvey ◽  
J. Williamson Balfe
Keyword(s):  
Mass Transfer ◽  
Body Weight ◽  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Surface Area ◽  
Peritoneal Surface ◽  
Unit Body Weight ◽  
Rapid Transport ◽  
Sick Children

Objective Measurement of mass transfer area coefficients (MTAC) in children of different sizes to determine if solute transport varies with age and to compare with published adult values. Design Mass transfer area coefficients calculated from prospectively collected data in 28 selected patients. Participants All children starting maintenance peritoneal dialysis at the Hospital for Sick Children. Selected patients were also studied if hospitalized for unrelated reasons. Results Mean MTAC values for creatinine and glucose were 4.0 and 4.5 mL/min, respectively, both considerably lower than adult values. When scaled per 70 kg body weight, these results were greater, and when scaled per 1.73 m2 surface area, they were lower than reported adult values. The MTAC/kg body weight was inversely correlated to age. Conclusions Solute transport in children is directly related to age and does not approach adult values until later childhood. However, more rapid transport per unit body weight is observed in children and may reflect an increased effective peritoneal surface area.

Peritoneal Transport Characteristics of Water, Low-Molecular Weight Solutes and Proteins during Long Term Continuous Ambulatory Peritoneal Dialysis

1986 ◽  
Vol 6 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Raymond T. Krediet ◽  
Elisabeth W. Boeschoten ◽  
Floris M.J. Zuyderhoudt ◽  
Lambertus Arisz
Keyword(s):  
Mass Transfer ◽  
Molecular Weight ◽  
Peritoneal Dialysis ◽  
Surface Area ◽  
Low Molecular Weight ◽  
Glucose Kinetics ◽  
Peritoneal Surface ◽  
Peritoneal Transport ◽  
Peritoneal Permeability

Peritoneal transport of water, low-molecular-weight solutes and proteins was studied on 75 occasions in 38 CAPD patients. Maximal ultrafiltration capacity decreased with time on CAPD, while there was an increase in the number of hypertonic bags used and the peritoneal absorption of glucose. A relationship was found between maximal ultrafiltration capacity and glucose kinetics. The duration of CAPD was longer in the patients with poor ultrafiltration, while they had a faster transport of glucose and creatinine, but not of proteins. In the group as a whole, no obvious changes were found in the mass transfer area coefficients of urea, creatinine and glucose, nor in the clearances of albumin and IgG. In the five patients with severe ultrafiltration loss, we found evidence of either decreased or increased peritoneal solute transport. Contrasting findings in transport of small solutes and proteins may reflect increased effective peritoneal surface area combined with decreased peritoneal permeability.

Transport of tracer albumin from peritoneum to plasma: role of diaphragmatic, visceral, and parietal lymphatics

1996 ◽  
Vol 270 (5) ◽  
pp. H1549-H1556 ◽  
Author(s):  
E. R. Zakaria ◽  
O. Simonsen ◽  
A. Rippe ◽  
B. Rippe
Keyword(s):  
Peritoneal Dialysis ◽  
Steady State ◽  
Peritoneal Cavity ◽  
Anterior Abdominal Wall ◽  
Membrane Surface ◽  
Peritoneal Membrane ◽  
Lymphatic Absorption ◽  
Capillary Walls ◽  
Lymphatic Pathways

Using a technique to acutely seal off various parts of the peritoneal membrane surface, with or without evisceration, we investigated the role of diaphragmatic, visceral, and parietal peritoneal lymphatic pathways in the drainage of 125I-labeled albumin (RISA) from the peritoneal cavity to the plasma during acute peritoneal dialysis in artificially ventilated rats. The total RISA clearance out of the peritoneal cavity (Cl) as well as the portion of this Cl reaching the plasma per unit time (Cl⇢ P) were assessed. Under non-steady-state conditions, the Cl was fivefold higher than the Cl⇢ P. Evisceration caused a 25-30% reduction in both Cl⇢ P and Cl. Sealing of the diaphragm, however, reduced the Cl⇢ P by 55% without affecting the Cl. A further reduction in the Cl⇢ P was obtained by combining sealing of the diaphragm with evisceration, which again markedly reduced the Cl. However, the greatest reduction in the Cl was obtained when the peritoneal surfaces of the anterior abdominal wall were sealed off in eviscerated rats. The discrepancy between the Cl and the Cl⇢ P can be explained by the local entrance of fluid and macromolecules into periabdominal tissues, where fluid is rapidly absorbed through the capillary walls via the Starling forces, while macromolecules are accumulating due to their very slow uptake by tissue lymphatics under non-steady-state conditions. Of the portion of the total Cl that rapidly entered the plasma, conceivably by lymphatic absorption, 55% could be ascribed to diaphragmatic lymphatics 30% to visceral lymphatics, and only some 10-15% to parietal lymphatics.

The Influence of Peritoneal Surface Area on Dialysis Adequacy

2005 ◽  
Vol 25 (3_suppl) ◽  
pp. 137-140 ◽  
Author(s):  
Michel Fischbach ◽  
Céline Dheu ◽  
Pauline Helms ◽  
Joëlle Terzic ◽  
Anne Cécile Michallat ◽  
...  
Keyword(s):  
Peritoneal Dialysis ◽  
Surface Area ◽  
Contact Area ◽  
Peritoneal Membrane ◽  
Dialysis Adequacy ◽  
Peritoneal Surface ◽  
Vascular Area ◽  
Fill Volume ◽  
Peritoneal Dialysis Fluid ◽  
Dialysis Fluids

In children, the prescription of peritoneal dialysis is based mainly on the choice of the peritoneal dialysis fluid, the intraperitoneal fill volume (mL/m2 body surface area (BSA)], and the contact time. The working mode of the peritoneal membrane as a dialysis membrane is more related to a dynamic complex structure than to a static hemodialyzer. Thus, the peritoneal surface area impacts on dialysis adequacy. In fact, the peritoneal surface area may be viewed as composed of three exchange entities: the anatomic area, the contact area, and the vascular area. First, in infants, the anatomic area appears to be twofold larger than in adults when expressed per kilogram body weight. On the other hand, the anatomic area becomes independent of age when expressed per square meter BSA. Therefore, scaling of the intraperitoneal fill volume by BSA (m2) is necessary to prevent a too low ratio of fill volume to exchange area, which would result in a functional “hyperpermeable” peritoneal exchange. Second, the contact area, also called the wetted membrane, is only a portion of the anatomic area, representing 30% to 60% of this area in humans, as measured by computed tomography. Both posture and fill volume may affect the extent of recruitment of contact area. Finally, the vascular area is influenced by the availability of both the anatomic area and the recruited contact area. This surface is governed essentially by both peritoneal vascular perfusion, represented by the mesenteric vascular flow and, hence, by the number of perfused capillaries available for exchange. This vascular area is dynamically affected by different factors, such as composition of the peritoneal fluid, the fill volume, and the production of inflammatory agents. Peritoneal dialysis fluids that will be developed in the future for children should allow an optimization of the fill volume owing to a better tolerance in terms of lower achieved intraperitoneal pressure for a given fill volume. Moreover, future peritoneal dialysis fluids should protect the peritoneal membrane from hyperperfusion (lower glucose degradation products).

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 peritoneal cavity lymphatic absorption in peritoneal dialysis

1987 ◽  
Vol 32 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Robert A. Mactier ◽  
Ramesh Khanna ◽  
Zbylut J. Twardowski ◽  
Karl D. Nolph
Keyword(s):  
Peritoneal Dialysis ◽  
Peritoneal Cavity ◽  
Lymphatic Absorption

scholarly journals Ultrafiltration Failure in Peritoneal Dialysis: A Pathophysiologic Approach

2015 ◽  
Vol 39 (1-3) ◽  
pp. 70-73 ◽  
Author(s):  
Isaac Teitelbaum
Keyword(s):  
Peritoneal Dialysis ◽  
Surface Area ◽  
Free Water ◽  
Fluid Loss ◽  
Free Water Clearance ◽  
Peritoneal Surface ◽  
Ultrafiltration Failure ◽  
Rapid Transport ◽  
Technique Failure ◽  
Sodium Sieving

Background: Ultrafiltration failure is a significant cause of technique failure for peritoneal dialysis and subsequent transfer to hemodialysis. Summary: Ultrafiltration failure is defined as failure to achieve at least 400 ml of net ultrafiltration during a 4 h dwell using 4.25% dextrose. Four major causes of ultrafiltration failure have been described. A highly effective peritoneal surface area is characterized by transition to a very rapid transport state with D/P creatinine >0.81. Low osmotic conductance to glucose is characterized by attenuation of sodium sieving and decreased peritoneal free water clearance to <26% of total ultrafiltration in the first hour of a dwell. Low effective peritoneal surface area manifests with decreases in the transport of both solute and water. A high total peritoneal fluid loss rate is the most difficult to diagnose clinically; failure to achieve ultrafiltration with an 8-10 h icodextrin dwell may provide a clue to diagnosis. Key Messages: Knowledge of the specific pathophysiology of the various causes of ultrafiltration failure will aid in the diagnosis thereof.

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