Peritoneal Ultrafiltration after Chronic Exposure to Dialysis Fluid

Eleven rats were given twice-daily intraperitoneal injections of 20 mL of dialysis fluid containing 4.5% glucose for 6 weeks. The peritoneal ultrafiltration capacity of this group was compared with that of a control group of 10 rats that had received no injections by measuring the volume and glucose concentration of the dialysate remaining in the peritoneal cavity 2 hours after injection. Animals that had received injections of dialysis fluid showed significant loss of peritoneal ultrafiltration: volume of dialysate remaining in the control group was 31 (13–35) mL, and in the experimental group was 25 (11–45) mL, with p<0.02 (Mann-Whitney). This was associated with enhanced glucose absorption: glucose absorbed by the control group was 382 (312–706) mg, and 595 (435–738) mg in the experimental group (p<0.002, Mann-Whitney).

Angiogenesis in peritoneal dialysis

Long-term exposure to peritoneal dialysis fluid induces morphological alterations, including angiogenesis, leading to a loss of ultrafiltration (UF) capacity. We discuss the effect of different factors in peritoneal dialysis (PD) on angiogenesis. In addition, we describe the process of angiogenesis and the possible role of different cell types in the peritoneum upon PD contributing to new blood vessel formation. Furthermore, we review several interventions used in our rat PD exposure model to decrease angiogenesis in PD. Moreover, we show new data on the use of sunitinib to inhibit angiogenesis in this rat model. Although various interventions seem to be promising, well-randomised clinical trials showing absolute prevention of angiogenesis and UF failure are, yet, still missing. To make real progress in PD treatment, the aim should be to prevent angiogenesis as well as peritoneal fibrosis and PD-induced inflammation.

Scanning and transmission electron microscopic study of visceral and parietal peritoneal regions in the rat

The visceral peritoneum of intraabdominal organs (spleen, stomach, liver, small intestine), omentum majus and the parietal peritoneum of the anterior abdominal wall and the diaphragm were studied in adult Wistar rats by combined scanning and transmission electron microscopy (SEM, TEM). In general, the peritoneal surface consisted of a mesothelium composed of cubic, flat or intermediate cell types delimited by a basal lamina. Cubic mesothelial cells predominated in parenchymal organs (spleen, liver) and were characterized by prominent and indentated nuclei, a cytoplasm richly supplied with organelles, a dense microvillous coat, basal invaginations and elaborate intercellular contacts. Flat mesothelial cells were observed in the intestinal, omental and parietal peritoneum (tendinous diaphragm, abdominal wall) and showed elongated nuclei, scant cytoplasm, a poorly developed organelle apparatus and sparsely distributed microvilli. An intermediate mesothelial cell type was described within the gastric peritoneum characterized by a central cytoplasmic protrusion at the nuclear region containing most of the cytoplasmic organelles and by thin finger-like cytoplasmic processes. The submesothelial connective tissue layer was composed of collagen fiber bundles, fibroblasts and free cells (macrophages, granulocytes, mast cells) and contained blood and lymphatic vessels. In the spleen, elastic fibers formed a membranous structure with intercalated smooth muscle cells. Mesothelial openings were observed as tunnel-like invaginations within the hepatic peritoneum and as clusters of peritoneal stomata within the parietal peritoneum of the anterior abdominal wall and the muscular diaphragm. The round or oval openings of the peritoneal stomata were frequently occluded by overlapping adjacent mesothelial cells and their microvillous coat or obstructed by cellular material. At the side of the peritoneal stomata the mesothelial cell layer was interrupted to allow a direct access to the underlying submesothelial lymphatic system. The mesothelium and lymphatic endothelium shared a common basal lamina. The endothelial cells were discontinuous and displayed valve-like plasmalemmatic interdigitations facilitating an intercellular transport of fluids and corpuscular elements from the peritoneal cavity to the submesothelial lymphatic lacunae. The findings underline the morphological heterogeneity of the peritoneum in visceral and parietal regions, suggesting different functional implications, and further support the presence of extra-diaphragmatic peritoneal stomata.

Membrane longevity in peritoneal dialysis: impact of infection and bio-incompatible solutions

As experience with peritoneal dialysis (PD) has improved and peritonitis rates have decreased, more patients are surviving for long periods on PD. Associated with this has been the recognition that there are unique complications of PD, specifically sclerosing syndromes and membrane failure that are most common in the long-term patient. Although anecdotal data would suggest that the long-term exposure to "bio-incompatable" fluids and or the occurrence of severe episodes of peritonitis are contributory in the pathogenesis of these diseases, cause and effect have not been proven. Normal peritoneal structure, changes that occur over time, and how the normal resident immune defense systems are altered with PD are reviewed. It is known that the continued loss of macrophages in the PD fluid results in an ever increasing percentage of immature cells in the peritoneum, which paradoxically are more reactive in terms of cytokine generation and less effective in host defense. The potential harmful effects of glucose and advanced glycosylation end products are also explored. The review concludes stating that further research is needed to better link the clinical syndromes with alterations in membrane structure/function.

Influence of intraperitoneal vancomycin on peritoneal dialysis efficiency. A clinical study

Peritonitis is a major complication of intermittent peritoneal dialysis (IPD); over 70% of the infections are caused by Gram-positive bacteria. Vancomycin (V) is the antibiotic of choice in the treatment of peritonitis caused by G(+). The influence of vancomycin on peritoneal transport in IPD patients has not been described before. We have investigated the effect of intraperitoneal vancomycin on dialysis efficiency in 8 IPD patients using dialysis solutions containing either lactate or acetate. The following parameters were measured: net ultrafiltration (UF), concentration ratios (D/P) of urea, creatinine, potassium, peritoneal clearances (ml/min) of urea, creatinine, potassium, mass transfer of sodium (MTNa), sodium sieving index (SCNa). It has been found that vancomycin significantly decreases D/P urea (p < 0.05) and creatinine (p < 0.05). We found also a significant decrease of mean clearance of urea (p < 0.05) and creatinine (p < 0.05). The mean clearance of potassium did not change significantly. There was no significant change in UF, MTNa, and SCNa. Our preliminary data suggest that vancomycin decreases the permeability of peritoneum for certain low molecules in IPD patients which may have a negative impact on dialysis efficiency.

The serous membranes in the cat. Electron microscopic observations

Visceral and parietal pleura, peritoneum and pericardium of 26 adult cats were studied by means of transmission electron microscopy. The main components of the three serous membranes follow a general plan: mesothelium, basal lamina (BL) and submesothelial connective tissue layer. They show significant diversities in both sheets of the three serous membranes in the different organs and regions. The elastic membrane under the BL is an obligatory component of the visceral pleura. Two basic cell types - high and flat, as well as intermediate and degenerative cell forms are described in the mesothelial layer. The high cells are especially characteristic of the visceral sheets, while the flat cells predominate in the parietal sheets. The involvement of the mesothelium in the homeostasis in the cavities is discussed. A detailed characteristic of the BL of both sheets and its variation in individual organs is presented. Varieties of cells, collagen and elastic fibers, blood and lymph capillaries of the connective tissue layers of the visceral and parietal sheets are described with special reference to their relation to different underlying tissues. An attempt to find a structure-functional correlation of these observations is made. The transport capability of the pleura and peritoneum is investigated by the intrapleural and intraperitoneal application of horseradish peroxidase (HRP).

Influence of intraperitoneal gentamicin on peritoneal transport in IPD patients

We have investigated the effect of intraperitoneal gentamicin on dialysis efficiency in 10 intermittent peritoneal dialysis (IPD) patients. The following parameters were measured: net ultrafiltration (UF); concentration ratios (D/P) of urea, creatinine, potassium; peritoneal clearances (ml/min) of urea, creatinine, potassium; mass transfer of sodium (MTNa); sodium sieving index (SCNa). It has been found that gentamicin significantly decreased D/P urea (p < 0.056) and D/P creatinine (p < 0.05). We found also a significant decrease of mean clearances of urea (p < 0.05) and creatinine (p < 0.05). The mean clearance of potassium did not significantly change. There was no significant change in UF, MTNa and SCNa. Our preliminary data suggest that gentamicin decreases the permeability of the peritoneum for certain low molecules in IPD patients, which may have a negative impact on dialysis efficiency.

Antibacterial activity of the dialysates and sera during treatment with chemotherapeutic combinations in continuous ambulatory peritoneal dialysis (CAPD)

In everyday clinical practice, different chemotherapeutics are mostly applied intraperitoneally in treating continuous ambulatory peritoneal dialysis (CAPD) peritonitis. Antibacterial activity of the dialysates and sera were studied, according to their bacteriostatic effect after the intraperitoneal and/or peroral administration of chemotherapy. All samples were tested by the two-fold dilution method. We found that the best therapeutical effect is obtained by applying the combination of two compatible chemotherapeutics, in which the first acts in the peritoneal cavity, and the other represents the "pool" of chemotherapeutics forming a barrier to the spreading of bacteria into other distant parts of the body.