Embryology, anatomy, physiology and pathophysiology of the peritoneum and the peritoneal vasculature.

The peritoneum is a large serous membrane with both epithelial and mesenchymal features, and is essential for maintaining an intra-abdominal homeostatic equilibrium. The peritoneum plays a central role in the pathogenesis of a number of disorders. Pathological processes affecting the peritoneum such as inflammation and carcinomatosis can have serious clinical consequences, but the pathophysiology of these conditions is poorly understood. Understanding peritoneal embryology, anatomy and physiology is crucial to comprehend pathophysiological mechanisms and to devise a new focus for research. The vascular response to pathological processes appears to be of considerable importance, since the peritoneal vasculature plays a pivotal role in most associated diseases. Therefore, this review summarizes currently available literature with special emphasis on the development, anatomy and function of the peritoneal vasculature. Pathological processes are described to illustrate physiological and pathophysiological characteristics of the peritoneum.

Role of allograft inflammatory factor-1 in the regulation of inflammation and oxidative stress in primary peritoneal mesothelial cells.

Peritoneal dialysis (PD) is often used to treat patients with end stage renal disease, and its long-term complications include excessive inflammation and oxidative stress. Allograft inflammatory factor 1 (AIF-1), as a cytoplasmic protein, is originally identified from infiltrating macrophages, and it was associated with inflammation in the cells other than macrophages, such as endothelial cells and vascular smooth muscle cells. To clarify the molecular mechanisms of AIF-1-modulated pathological changes in the peritoneum during PD, we first detected the AIF-1 expression in peritoneal tissues from PD mice. Results revealed that the pro-fibrotic stimulation caused AIF-1 upregulation and triggered inflammation in peritoneal tissues, and that AIF-1 co-expressed with pan-cytokeratin (a marker of peritoneal mesothelial cells). We next treated primary mouse peritoneal mesothelial cells (pan-cytokeratin and intercellular adhesion molecule 1 positive cells) with 50 or 100 ng/mL recombinant AIF-1, and evaluated the direct effects of AIF-1 on these cells in vitro. We found that exogenous AIF-1 treatment induced inflammation and oxidative stress in mesothelial cells. Apart from the augmented IL-6 and TNF-α secretion, the level of ROS was upregulated and the activity of anti-oxidative SOD was reduced in cells exposed to AIF-1. Moreover, AIF-1 simulation triggered the activation of NF-κB pathway-enhanced the conversion of IκB to phosphorylated IκB and promoted the translocation of NF-κB p65 from cytoplasm into nucleus. Additionally, AIF-1-evoked inflammation in peritoneal mesothelial cells was attenuated by the addition of NF-κB inhibitor (BAY 11-7082). In brief, this study provides us novel information to understand the molecular regulation mechanisms of AIF-1 in peritoneal fibrosis.

The peritoneal "soil" for a cancerous "seed": a comprehensive review of the pathogenesis of intraperitoneal cancer metastases.

Various types of tumors, particularly those originating from the ovary and gastrointestinal tract, display a strong predilection for the peritoneal cavity as the site of metastasis. The intraperitoneal spread of a malignancy is orchestrated by a reciprocal interplay between invading cancer cells and resident normal peritoneal cells. In this review, we address the current state-of-art regarding colonization of the peritoneal cavity by ovarian, colorectal, pancreatic, and gastric tumors. Particular attention is paid to the pro-tumoral role of various kinds of peritoneal cells, including mesothelial cells, fibroblasts, adipocytes, macrophages, the vascular endothelium, and hospicells. Anatomo-histological considerations on the pro-metastatic environment of the peritoneal cavity are presented in the broader context of organ-specific development of distal metastases in accordance with Paget's "seed and soil" theory of tumorigenesis. The activity of normal peritoneal cells during pivotal elements of cancer progression, i.e., adhesion, migration, invasion, proliferation, EMT, and angiogenesis, is discussed from the perspective of well-defined general knowledge on a hospitable tumor microenvironment created by the cellular elements of reactive stroma, such as cancer-associated fibroblasts and macrophages. Finally, the paper addresses the unique features of the peritoneal cavity that predispose this body compartment to be a niche for cancer metastases, presents issues that are topics of an ongoing debate, and points to areas that still require further in-depth investigations.

The peritoneum: healing, immunity, and diseases.

The peritoneum defines a confined microenvironment, which is stable under normal conditions, but is exposed to the damaging effect of infections, surgical injuries, and other neoplastic and non-neoplastic events. Its response to damage includes the recruitment, proliferation, and activation of a variety of haematopoietic and stromal cells. In physiological conditions, effective responses to injuries are organized; inflammatory triggers are eliminated; inflammation quickly abates; and the normal tissue architecture is restored. However, if inflammatory triggers are not cleared, fibrosis or scarring occurs and impaired tissue function ultimately leads to organ failure. Autoimmune serositis is characterized by the persistence of self-antigens and a relapsing clinical pattern. Peritoneal carcinomatosis and endometriosis are characterized by the persistence of cancer cells or ectopic endometrial cells in the peritoneal cavity. Some of the molecular signals orchestrating the recruitment of inflammatory cells in the peritoneum have been identified in the last few years. Alternative activation of peritoneal macrophages was shown to guide angiogenesis and fibrosis, and could represent a novel target for molecular intervention. This review summarizes current knowledge of the alterations to the immune response in the peritoneal environment, highlighting the ambiguous role played by persistently activated reparative macrophages in the pathogenesis of common human diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A counterforce to diversion of cerebrospinal fluid during ventriculoperitoneal shunting: the intraperitoneal pressure. An observational study.

BACKGROUND: Intraperitoneal pressure (IPP) counteracts the diversion of cerebrospinal fluid (CSF) from the cranial to the peritoneal compartment during ventriculoperitoneal shunting. Animal studies suggest that the intrinsic IPP exceeds the intraperitoneal hydrostatic pressure. The intrinsic IPP in mobile patients is relevant for shunt therapy, but data about it is not available. METHODS: The IPP was measured indirectly in 25 mobile subjects (13 female) by applying a standard intravesical pressure measurement technique. Measurements were carried out in reference to the navel (supine position) and the xiphoid (upright position). Results were adjusted for the intraperitoneal hydrostatic pressure and correlated afterward with general body measures. RESULTS: The corrected mean (SD) IPP measured in the supine position was 4.4 (4.5) cm H2O, and the mean (SD) upright IPP was 1.6 (7.8) cm H2O (p = 0.02). A positive correlation was found between the body mass index (BMI) and the IPP in the upright (r = 0.51) and supine (r = 0.65) body positions, and between the abdominal circumference and the IPP in the supine position (r = 0.63). CONCLUSIONS: The intrinsic IPP in mobile subjects exceeds the intraperitoneal hydrostatic pressure. Thus, the intrinsic IPP counteracts the diversion of CSF into the peritoneal compartment. The intrinsic IPP is correlated with mobile patients' general body measures.

Impact of Diabetes on Extracellular Volume Status in Patients Initiating Peritoneal Dialysis.

BACKGROUND: Recent reports have highlighted that diabetic patients with kidney failure are at increased risk of technique failure and transfer to haemodialysis within 90 days of initiating peritoneal dialysis (PD). We wished to determine whether there were differences between diabetic and non-diabetic patients within the first 3 months of starting PD. METHODS: We reviewed results of corresponding bioimpedance and the 1st test of peritoneal membrane function (PET) in consecutive patients, 6-10 weeks after initiating PD electively. RESULTS: Adult patients numbering 386 - 230 males (59.6%), 152 (39.4%) diabetic, 188 (48.7%) white, mean age 57.3 ±16.9 years - were studied. Although weight, residual renal function and peritoneal clearances were not different, diabetic patients had greater extracellular water to total body water (ECW/TBW; 40.4 ± 1.1 vs. 39.2 ± 1.4) and % ECW excess (9.6 [6.3-12.3] vs. 4.9 [0.7-8.9]), lower serum albumin (35.2 ± 4.7 vs. 37.8 ± 4.9 g/L), greater fat mass index (9.5 ± 4.2 vs. 7.7 ± 4.2), and although mean arterial blood pressure was similar, arterial pulse pressure was greater (66.9 ± 10.8 vs. 54.3 ± 17.3 mm Hg, all p < 0.001). On multivariate analysis, glycated haemoglobin was associated with pulse pressure (standardised ß 0.24, p < 0.001), N terminal brain natriuretic peptide (ß 0.24, p < 0.001), ECW/TBW (ß 0.19, p = 0.012) and negatively with serum albumin (ß -0.14, p = 0.033) and creatinine (ß -0.18, p = 0.02). CONCLUSION: Diabetic patients electively starting PD were found to have greater ECW/TBW ratios and ECW excess 6-10 weeks after starting PD compared to non-diabetics, despite similar PET. Increased ECW could predispose diabetic patients to be at greater risk of volume overload.

The Peritoneum: Health, Disease, and Perspectives regarding Tissue Engineering and Cell Therapies.

There are several pathologies associated with the peritoneum, such as mesothelioma and peritonitis. Moreover, the peritoneum is widely used in ultrafiltration procedures, i.e., peritoneal dialysis, presenting advantages over hemodialysis. On the other hand, ultrafiltration failure may lead to dialysis-induced fibrosis and hypervolemia. Therefore, the pathophysiological study of this tissue is of extreme biomedical importance. Studies investigating the biology of the cells dwelling in the peritoneum wall provide evidence of their plasticity and progenitor features. For instance, both mesothelial and submesothelial cells present characteristics similar to mesenchymal stem cells, including osteogenic and adipogenic differentiation potential, support of extramedullary hematopoiesis, modulation of inflammatory responses, and regulation of tumor progression. Indeed, the participation of each cell type in peritoneal pathological and physiological phenomena is still under debate, especially regarding a possible differentiation pathway connecting these peritoneal cells. The primary aim of this review is to raise this discussion. In order to do so, we will firstly provide an overview of the peritoneum anatomy, histology, and ontology, and finally we will address how a better understanding of peritoneal cell biology may contribute to future cell therapy and tissue engineering approaches.

The Current State of Peritoneal Dialysis.

Technical innovations in peritoneal dialysis (PD), now used widely for the long-term treatment of ESRD, have significantly reduced therapy-related complications, allowing patients to be maintained on PD for longer periods. Indeed, the survival rate for patients treated with PD is now equivalent to that with in-center hemodialysis. In parallel, changes in public policy have spurred an unprecedented expansion in the use of PD in many parts of the world. Meanwhile, our improved understanding of the molecular mechanisms involved in solute and water transport across the peritoneum and of the pathobiology of structural and functional changes in the peritoneum with long-term PD has provided new targets for improving efficiency and for intervention. As with hemodialysis, almost half of all deaths on PD occur because of cardiovascular events, and there is great interest in identifying modality-specific factors contributing to these events. Notably, tremendous progress has been made in developing interventions that substantially reduce the risk of PD-related peritonitis. Yet the gains have been unequal among individual centers, primarily because of unequal clinical application of knowledge gained from research. The work to date has further highlighted the areas in need of innovation as we continue to strive to improve the health and outcomes of patients treated with PD.

Regeneration of peritoneal mesothelial cells after placement of hyaluronate carboxymethyl-cellulose (Seprafilm®).

PURPOSE: To examine the regeneration of mesothelium under a bioresorbable membrane. METHODS: A 1 cm2 piece of peritoneum was resected from both sides of the abdominal wall of retired female mice. A piece of hyaluronate and carboxymethyl-cellulose (Seprafilm®) was placed over the wound on one side and the other side was left uncovered. We evaluated the degree of adhesion and regeneration of mesothelial cells macroscopically and histologically using immunohistochemistry at different times. RESULTS: Macroscopically, the degree of postoperative adhesion in the treated site was significantly less than that in the untreated site. The membrane was left in place for 7 postoperative days (PODs). By POD 5, the regenerated peritoneum mesothelial cells covered part of the area and by POD 7, they had regenerated over almost all of that area in the abdominal wall. CONCLUSION: The anti-adhesion membrane worked as a physical barrier to prevent postoperative adhesion until the mesothelial cells had regenerated completely. To our knowledge, this is the first study conducted to assess the regeneration of peritoneum mesothelial cells under a bioresorbable membrane using immunohistochemistry.

Subperitoneal extension of disease processes between the chest, abdomen, and the pelvis.

The subserous space is a large, anatomically continuous potential space that interconnects the chest, abdomen, and pelvis. The subserous space is formed from areolar and adipose tissue, and contains branches of the vascular, lymphatic, and nervous systems. As such, it provides one large continuous space in which many disease processes can spread between the chest, abdomen, and the pelvis.

Oral paricalcitol versus oral calcitriol in continuous ambulatory peritoneal dialysis patients with secondary hyperparathyroidism.

BACKGROUND: Secondary hyperparathyroidism (SHPT) is common in end-stage renal disease. Our primary objective was to evaluate the efficacy of oral paricalcitol versus oral calcitriol on serum intact parathyroid hormone (iPTH) and mineral bone parameters in continuous ambulatory peritoneal dialysis (CAPD) patients with SHPT. The secondary objective was to analyze highly sensitive C-reactive protein (hsCRP) and peritoneal membrane function in both groups. METHODS: This was a prospective randomized control trial. CAPD patients with SHPT were randomized to paricalcitol or calcitriol for 15 weeks. Serum intact iPTH, calcium, phosphate and alkaline phosphatase (ALP) were measured at baseline and every 3 weeks. Serum hsCRP and peritoneal membrane functions were measured at baseline and at week 15. RESULTS: A total of 26 patients were enrolled and randomized-12 to paricalcitol and 14 to calcitriol. Serum iPTH reduced significantly in both groups and there was no difference in the incidence of ≥50 % reduction of iPTH between both groups. There was a significant increase in serum calcium in both groups but there were no differences in serum phosphorus across the visits. The incidence of hypercalcemia was the same in both groups. Serum calcium-phosphorus (Ca × P) product increased in the paricalcitol group but decreased in the calcitriol group. Serum ALP decreased significantly in both groups. There were also no differences in pre- and post-treatment serum hsCRP and peritoneal function test (PFT) in both groups. CONCLUSION: Both oral paricalcitol and calcitriol were equally efficacious in reducing serum iPTH but were associated with significantly higher serum calcium. Serum Ca × P product increased in the paricalcitol group and decreased in the calcitriol group. Serum hsCRP level and PFT were not affected by either treatment. A larger randomized controlled trial is indicated to confirm these initial findings.

Astragalus membranaceus inhibits peritoneal fibrosis via monocyte chemoattractant protein (MCP)-1 and the transforming growth factor-ß1 (TGF-ß1) pathway in rats submitted to peritoneal dialysis.

Inflammation and transforming growth factor-ß1 (TGF-ß1) contribute to the development of peritoneal fibrosis (PF), which is associated with peritoneal dialysis (PD). Astragalus membranaceus (Astragalus) has anti-inflammatory and anti-fibrotic effects in many diseases. The goal of this study was to determine the anti-fibrotic effects of Astragalus on the PF response to PD. A rat model of PD was induced using standard PD fluid, and PF was verified by HE and Masson's staining, as well as through the expression of fibroblast surface protein (FSP) and collagen III. The expression levels of monocyte chemoattractant protein (MCP)-1, F4/80 (macrophage/monocyte marker in rat), TGF-ß1 and the downstream proteins phospho-SMAD 2/3 in dialyzed peritoneal tissue treated with or without Astragalus was evaluated using immunohistochemistry analysis. Overall correlations between MCP-1 and TGF-ß1 staining were analyzed using both the Spearman and Pearson methods. The results showed that Astragalus could inhibit the recruitment and activation of monocytes/macrophages, thereby reducing the production of TGF-ß1 in the dialyzed peritoneal membrane. PF was also significantly decreased following treatment with Astragalus. MCP-1 expression had a strong positive correlation with TGF-ß1 sensitivity, suggesting that the anti-fibrotic function of Astragalus was mediated by MCP-1 and the TGF-ß1 pathway. Our results indicate that Astragalus could be a useful agent against PD-induced PF.

Pelvic peritoneum in male armadillo and anteater (Xenarthra, Mammalia): a comparative survey.

The literature supports the hypothesis that the pelvic excavation is the bottom of the abdominal cavity, which is covered by the peritoneal serous membrane in order to promote visceral dynamics. We studied the peritoneum in eight specimens of Xenarthra (Euphractus sexcinctus, Myrmecophaga tridactyla and Tamandua tetradactyla). The animals were fixed in formaldehyde (10%). For description and analyzes of the pelvic peritoneum, dissection and photo documentation were performed. We saw that the parietal serous membrane reflected, involving the pelvic viscera. The urorectal septum is the floor of the higher pelvis as a serosa reflection between the bladder and the rectum. The bladder and gonads are completely peritonized in adult armadillo. In anteaters and young armadillos, the testicles are in a position analogous to the uterus, joined by the conjunctive septum at the midline and along with the bladder, they partially project to the higher and lower pelvis. In Myrmecophagidae, vesicogenital, rectogenital and sacrorectal recesses were observed. In Dasypodidae, the recesses are similar to those of other recent vertebrates.

Pilot study evaluating the efficacy of AlloMEM™ for prevention of intraperitoneal adhesions and peritoneal regeneration after loop ileostomy.

OBJECTIVE: This study was designed to evaluate the feasibility of AlloMEM™, a novel lyophililzed human peritoneal membrane, at peritoneal reconstitution, and decreasing adhesion formation after temporary loop ileostomy. METHODS: In a pilot study, ten patients had AlloMEM™ used during elective formation of a temporary diverting loop ileostomy for benign or malignant colorectal disease. A blinded investigator and the operating surgeon analyzed the change in adhesion formation and peritoneal remodelling using ileostomy mobilization time and a 5-point adhesion scale grading intra-abdominally and at the subcutaneous and fascial levels. RESULTS: The mean body mass index was 31 [standard deviation (SD) 5.6], and 40 % of patients had previous abdominal surgery. Ileostomies were reversed after a mean 14 weeks (SD 6.0). The mean ileostomy mobilization time was 27.2 min (SD 12.0). From baseline to ileostomy reversal, there were significant increases in adhesions at the subcutaneous (p = 0.0002) and fascial levels (p = 0.0024). The increased subcutaneous adhesions were associated with improved peritoneal remodeling. There was no significant increase in adhesions from baseline to ileostomy reversal at the intra-abdominal points (p = 0.9393) or around the ileostomy site (p = 0.6128). The median hospital length of stay was 2.6 days (range, 2-3). A single adverse event related to product packaging led to redesign of the packaging process. CONCLUSIONS: Use of AlloMEM™ in ileostomy closures suggested improvement in adhesions around the fascia and promotion of peritoneal remodeling. AlloMEM™ was safe, feasible, and easy to use in this pilot study. Comparative research is needed to assess the outcomes with this novel product.

Intraperitoneal administration of local anesthetics in laparoscopic surgery: pharmacological, anatomical, physiological and pathophysiological considerations.

Local anesthetics, because of their ability to cause a reversible blockade in transmission of impulses along the central and peripheral neural pathways are used to induce analgesia. In laparoscopic surgery procedures, the reduction of postoperative pain is one of the biggest benefits compared with open surgery. However, the pain is not completely absent after laparoscopic surgery. The intraperitoneal administration of local anesthetic intraoperatively in laparoscopic surgery can reduce the intensity of postoperative pain. This method has been in use since the early nineties and seems to be effective. The purpose of this review is to assess the pharmacology of local anesthetics, the anatomy and physiology of the peritoneum, the physiology of preemptive analgesia, and the pathophysiology of pain and review the data from the use of this method so as to make it more effective. For the safest and longest intraperitoneal administration of local anesthetics the following significant points must be taken into consideration: administration of local anesthetic should be done at the beginning, in short-term intervention and both at the beginning and end of surgery for longer-term intervention, administration of local anesthetic should be combined with a vasoconstrictor, usage of solutions of small volume and high concentration of local anesthetic, coverage of the greatest possible surface of the parietal peritoneum (by using a nebulizer), adherence to a waiting period of 10-15 minutes after administration of local anesthetic and usage of a safe and longer duration local anesthetic like levobupivacaine.

Impact of intraperitoneal pressure of a CO2 pneumoperitoneum on the surgical peritoneal environment.

BACKGROUND: Animal experiments have suggested that a high intraperitoneal pressure (IPP) might adversely affect the surgical peritoneal environment. The present experimental study investigates the impact of IPP of a CO(2) pneumoperitoneum on human peritoneum. METHODS: Patients undergoing laparoscopic surgery were subjected to either low (8 mmHg) or standard (12 mmHg) IPP. Normal peritoneum was collected from the parietal wall at the beginning of surgery and every 60 min thereafter. Expression levels of 168 genes that encode extracellular matrix proteins, adhesion molecules or inflammatory cytokine signaling molecules were measured in peritoneal tissues using real-time polymerase chain reaction (PCR)-based assay panels. Human peritoneal mesothelial cells (HPMCs) and human peritoneal fibroblasts (HPFBs) were incubated in a CO(2) insufflation chamber for 1 h at 12 or 8 mmHg. Hyaluronan (HA) synthesis and mRNA expression levels of hyaluronic acid synthases (HAS) and hyaluronidases (Hyal) in HPMCs and HPFBs were measured at 0, 4, 8, 12, 24 and 48 h after CO(2) gas exposure by ELISA and real-time PCR, respectively. RESULTS: Expression levels of connective tissue growth factor (CTGF), matrix metalloproteinase-9, E-selectin, chemokine (C-X-C motif) ligand 2 (CXCL-2), Hyal-1 and Hyal-2 were significantly higher and those of HAS-1, HAS-3, thrombospondin-2 (TSP-2) and interleukin-10 were significantly lower in the 12 mmHg group compared with the 8 mmHg group. HA synthesis was significantly lower in the 12 mmHg group compared with the 8 mmHg group in HPMCs and HPFBs throughout the time course. CONCLUSIONS: A low IPP (8 mmHg) may be better than the standard IPP (12 mmHg) to minimize the adverse impact on the surgical peritoneal environment during a CO(2) pneumoperitoneum.

Biocompatible peritoneal dialysis solution preserves residual renal function.

BACKGROUND/AIMS: The long-term effects of biocompatible peritoneal dialysis (PD) solution on residual renal function (RRF), inflammation, adipokines and metabolic acidosis are controversial. We evaluated the effects of biocompatible PD solution in continuous ambulatory PD (CAPD) patients for an additional 12-month period. METHOD: Among 91 incident patients who started CAPD with either biocompatible PD solution (Balance®, Fresenius; LS, n = 48) or conventional PD solution (CAPD/DPCA®, Fresenius; CS, n = 43), 63 patients, who were followed for 12 months, were enrolled and followed for an additional 12 months. RESULTS: After 24 months of treatment, the glomerular filtration rate (GFR) of the LS group was twofold higher compared to the CS group (33.5 ± 30.7 vs. 16.3 ± 17.9 l/week/1.73 m(2), respectively, p = 0.021). In a subgroup of patients with an initial GFR >2 ml/min/1.73 m(2), the GFR of the LS group was significantly higher than the rate of the CS group after 24 months (43.7 ± 30.5 vs. 18.6 ± 19.0 l/week/1.73 m(2), respectively, p = 0.042). Over a 24-month period, effluent cancer antigen-125 levels were significantly increased in the LS group compared to the CS group, while effluent interleukin-6 levels did not differ between the two groups. The serum tCO(2) levels were consistently higher in the LS group compared to the CS group. CONCLUSIONS: We found that the effect of LS on preserving RRF may be maintained over a 24-month treatment period in CAPD patients, and LS use may have other benefits, such as the correction of metabolic acidosis.

[The presence and localization of heat shock protein 70 in rat mast cells].

Heat shock protein 70 (Hsp70) is considered not only as a cytosolic stress protein, but also as an extracellular molecule with immunomodulatory and signaling functions that play a role in adaptation to stress on cellular and systemic levels. The active involvement of mast cells in adaptation to stress may be associated with the presence of Hsp70 in secretory granules. Using immunoelectron microscopy, we showed that Hsp70 localized in secretory granules of rat pericardial and peritoneal mast cells. Localization of Hsp70 in rat perinoneal mast cells isolated by centrifugation on Percoll was confirmed by immunoblotting. The proposed involvement of mast cells in production of extracellular Hsp70 and possible functions of Hsp70 inside the mast cells granules are discussed.

Use of icodextrin solution to evaluate peritoneal transport capacity.

Peritoneal equilibration test (PET) is the gold standard for evaluating peritoneal transport, and measurement of the drain volume after 4-h dwell time with glucose 4.25% is a simple means of evaluating failure of ultrafiltration. The study objective was to verify if the measurement of the volume drained after 4 h dwell of icodextrin at 7.5% (ICO), has a better correlation with the parameters of PET. Patients in a peritoneal dialysis program (N = 35) underwent three procedures: PET; determination of the drain volume after a 4-h dwell with glucose 4.25%; and determination of the drain volume after a 4-h dwell with ICO. Among patients who were classified as high transporters, the ultrafiltration volume was greater after ICO use. The ICO ultrafiltration volume correlated negatively with the ratio between the 4- and 0-h dialysate glucose concentrations (D4/D0 ratio, r = -0.579; P = 0.002), correlating positively with the dialysate-to-plasma ratio for creatinine (D/PCr ratio, r = 0.474; P = 0.002). For ICO, the area under the receiver operating characteristic curve was 0.867 and 0.792 for the D/PCr and D4/D0 ratios (P < 0.0001 and P = 0.004, respectively), compared with 0.738 and 0.710 for glucose 4.25% (P = 0.020 and P = 0.041, respectively). A cut-off volume of 141 mL discriminated high/high-average transporters from low/low-average transporters. Volume drained after ICO use better predicts peritoneal transport patterns than does that drained after the use of glucose 4.25%.