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Encapsulating peritoneal sclerosis (EPS) is a rare but serious complication of peritoneal dialysis (PD). This review discusses the current understanding of the aetiology and pathogenesis of EPS, highlighting histological features which differentiate it from simple sclerosis of the peritoneal membrane which develops with time on PD. Diagnostic criteria are presented, including the role of imaging techniques. To date there are no randomised controlled trials to guide therapy; however, surgical techniques are an important treatment option. Collaborative research will be essential if this serious problem facing PD is to be solved.

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Composites comprised of calcium-deficient hydroxyapatite (HAp) and biodegradable polyphosphazenes were formed via cement-type reactions at physiologic temperature. The composite precursors were produced by blending particulate hydroxyapatite precursors with 10 wt% polymer using a solvent/non-solvent technique. HAp precursors having calcium-to-phosphate ratios of 1.5 (CDH) and 1.6 (CDS) were used. The polymeric constituents were poly[bis(ethyl alanato)phosphazene] (PNEA) and poly[(ethyl alanato)(1) (p-phenylphenoxy)(1) phosphazene] (PNEA(50)PhPh(50)). The effect of incorporating the phenyl phenoxy group was evaluated as a means of increasing the mechanical properties of the composites without retarding the rates of HAp formation. Reaction kinetics and mechanistic paths were characterized by pH determination, X-ray diffraction analyses, scanning electron microscopy, and infrared spectroscopy. The mechanical properties were analyzed by compression testing. These analyses indicated that the presence of the polymers slightly reduced the rate HAp formation. However, surface hydrolysis of polymer ester groups permitted the formation of calcium salt bridges that provide a mechanism for bonding with the HAp. The compressive strengths of the composites containing PNEA(50)PhPh(50) were superior to those containing PNEA, and were comparable to those of HAp produced in the absence of polymer. The current composites more closely match the structure of bone, and are thus strongly recommended to be used as bone cements where high loads are not expected.

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Aspects of the formation of bone analog composites at 37 degrees C are described. The composites are composed of hydroxyapatite (HAp) and the calcium salt of a biocompatible polymer and are capable of forming under in vivo conditions. Composite formation involves the formation of monolithic HAp from particulate calcium phosphate precursors while Ca ions liberated to the aqueous medium in which this reaction is occurring form crosslinks with the acidic polymer. The reactants are poly[bis(carboxylatophenoxy)phosphazene] (acid-PCPP), tetracalcium phosphate [Ca4(PO4)2O, TetCP], and anhydrous dicalcium phosphate (CaHPO4, DCPA). The effects of the proportion of polymer (5, 10, or 15 wt %) on the kinetics of HAp formation were studied. Compositional evolution of the solid calcium phosphates present was followed by X-ray diffraction and infrared spectroscopy analyses. HAp formation through a dissolution-precipitation process provided a mildly alkaline medium suitable for deprotonation of the acid-PCPP and for the formation of the calcium crosslinks, as monitored by infrared spectroscopy. Concurrence of crosslinking of the polymer and HAp formation was established, indicating true composite formation can be realized at physiologic temperature.

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There is increasing evidence that routine preoperative duplex scanning ultrasound cannot only increase the utilisation of native AVF for dialysis access but also allow proper selection of a target vessel with adequate luminal diameter to improve outcome. A minimum arterial diameter of 2mm is associated with successful fistula formation. A threshold for minimal venous diameter is difficult to establish. Most clinical studies use a value of 2.5mm for AVF and 4mm for prosthetic grafts. Traditional contrast venography is mandatory where there is suspicion of central vein stenosis. In predialysis patients where there is a risk of contrast nephropathy MR venography is emerging as a possible alternative.

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The low temperature synthesis of composites potentially suitable as bone substitutes which form in vivo, was investigated. The composites were comprised of stoichiometric hydroxyapatite (SHAp) and water-soluble poly phosphazenes. These constituents were selected because of their biocompatibility, and were mixed as powders with a phosphate buffer solution (PBS) to form the composites. The effects of poly[bis(sodium carboxylatophenoxy)phosphazene] (Na-PCPP) or poly[bis(potassium carboxylatophenoxy) phosphazene] (K-PCPP) on stoichiometric hydroxyapatite (SHAp) formation from tetracalcium phosphate and anhydrous dicalcium phosphate were assessed. The kinetics and reaction chemistries of composite formation were followed by isothermal calorimetry, X-ray diffraction, infrared spectroscopy and scanning electron microscopy. In the presence of 1% by weight of polyphosphazenes, composites comprised of SHAp and calcium cross-linked polymer salts were formed. Thus a mechanism for binding between polymer chains was established. Elevated proportions (5 and 10% by weight) of polyphosphazene, however, resulted in the inhibition of SHAp formation. This is attributed to the formation of viscous polymer solution coatings on the calcium phosphate precursors, retarding their reaction, and consequently inhibiting SHAp formation.

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The formation of biodegradable composites which may be suitable as bone analogs is described. Polyphosphazene-hydroxyapatite (HAp) composites were produced via an acid-base reaction of tetracalcium phosphate and anhydrous dicalcium phosphate in the presence of polyphosphazenes bearing alkyl ester containing side-groups. The polyphosphazenes used were poly(ethyl oxybenzoate)phosphazene (PN-EOB) and poly(propyl oxybenzoate) phosphazene (PN-POB). The effects of temperature and the proportions of polymers, PN-EOB and PN-POB on the kinetics, reaction chemistry and phase evolution during the formation of stoichiometric HAp were studied. Kinetics, phase evolution and microstructural development were evaluated using isothermal calorimetry, X-ray diffraction and scanning electron microscopy, respectively. Analysis of solution chemistry revealed that the increases in the pH during the formation of SHAp, resulted in partial hydrolysis of the polymer surfaces, which led in turn to the formation of a calcium cross-linked polymer surface. The calcium cross-linked polymer surface appeared to facilitate the nucleation and growth of apatite deposits on the polymer. The current study illustrates the in situ formation of HAp in the presence of polyphosphazenes, where HAp is chemically bonded to the polymer.

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AIM: To review the published literature comparing the diagnostic accuracy of magnetic resonance angiography (MRA) with and without gadolinium in diagnosing renal artery stenosis, using catheter angiography as reference. MATERIALS AND METHODS: A meta-analysis was performed of English language articles identified by computer search using PubMed/MEDLINE, followed by extensive bibliography review from 1985 to May 2001. Inclusion criteria were: (1) blinded comparison with catheter angiography; (2)indication for MRA stated; (3) clear descriptions of imaging techniques; and (4) interval between MRA and catheter angiography < 3 months and only the largest of all studies from one centre was selected in the analysis. RESULTS: A total of 39 studies were identified, of which 25 met the inclusion criteria. The number of patients included in the meta-analysis was 998: 499 with non-enhanced MRA and 499 with gadolinium-enhanced MRA. The sensitivity and specificity of non-enhanced MRA were 94% (95% CI: 90-97%) and 85% (95% CI: 82-87%), respectively. For gadolinium-enhanced MRA sensitivity was 97% (95% CI: 93-98%) and specificity was 93% (95% CI: 91-95%). Thus, specificity and positive predictive value were significantly better for gadolinium-enhanced MRA (P < 0.001). Accessory renal arteries were depicted better by gadolinium-enhanced MRA (82%; 95% CI: 75-87%) than non-gadolinium MRA (49%; 95% CI: 42-60%) (P < 0.001). CONCLUSIONS: Gadolinium-enhanced MRA may replace arteriography in most patients with suspected renal artery stenosis, and has major advantages in that it is non-invasive, avoids ionizing radiation and uses a non-nephrotoxic contrast agent.

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Sclerosing encapsulating peritonitis (SEP) is a serious complication of peritoneal dialysis (PD). Previous reports place the prevalence of SEP at 0.54%-7.3%. We estimated the prevalence of SEP in our unit to be 1.4% over the period 1989-1999. We here present the 6 identified cases. All of the patients presented with small-bowel obstruction; hemorrhagic ascites was identified in 3 cases. All 6 patients experienced ultrafiltration inadequacy, and 5 were treated with glucose polymer (icodextrin; duration of treatment: 1 month-2.5 years). Peritoneal dialysis was stopped at the time of diagnosis in 2 cases. In the other 4 cases, PD had been withdrawn some time prior to the SEP being diagnosed (2 weeks-5 years). Five of the patients have died; the 6th currently uses hemodialysis.

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AIM: To determine whether an optimal site of injection exists for herniography. MATERIALS AND METHODS: This was a prospective, randomized study of 93 consecutive patients who were referred for herniography over a period of 9 months. Patients underwent either a left iliac fossa (LIF) or midline puncture. Parameters assessed included initial adequate needle placement, complications, pain scores and body mass index (BMI). The groups were compared using Chi-squared test for categorical data, Student's t-test for continuous data and the Mann-WhitneyU-test for skewed data, withP < 0.05 considered statistically significant RESULTS: Four complications were encountered (4%), and these were equally distributed between the two groups. Adequate initial positioning of the needle was similar in both groups. The volume of local anaesthetic used was correlated with discomfort using a pain scale: a volume of >6 ml resulted in significantly more pain. More frequent initial adequate needle placement was observed in thin patients (BMI < 45 kg/m(2)) with experienced operators. Conversely, increased body mass index resulted in more difficult needle placement. CONCLUSION: Herniography is a safe procedure with few complications. There was no significant difference comparing the midline and LIF approaches.Nadkarni, S.et al. (2001). Clinical Radiology56, 389-392.

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The effects of wollastonite on the mechanical properties and in vitro behavior of hydroxyapatite-Ca polyacrylate composites were studied. Powder mixtures of tetracalcium phosphate, poly(acrylic-co-itaconic), and wollastonite fibers (< or =75% by weight) were hot-pressed for 30 min at 300 degrees C and 60 kpsi. Tensile strengths, elastic moduli, and microstructures of the composites were investigated. The tensile strengths of these composites were improved by the addition of wollastonite fibers, whereas the elastic moduli decreased. The highest value of tensile strength (approximately 155 MPa) was achieved by the addition of 40% wollastonite. Composites were immersed in simulated body fluid (SBF) for up to 14 days and then in 1.5 SBF for a week. The changes in the concentrations of Ca, Si, and P ions and the pH of these solutions indicate bioactivity. An evaluation of the microstructures of the composites after SBF immersion indicated that apatite layers had formed on the surfaces of the composites.

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The formation of biocompatible organic-inorganic composites by reactions between tetracalcium phosphate (Ca4(PO4)2O, TetCP) and the biomedical polymer poly(vinyl phosphonic acid) (PVPA) is described. Composites were prepared by hot pressing mixtures of these powders at 80 kpsi and 300 degrees C for 30 min. Composite formation was investigated depending on the proportions of reactants and the processing route used. Two inorganic phases were produced as a result of the acid-base reaction between TetCP and PVPA: hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and anhydrous dicalcium phosphate (CaHPO4, DCPA). The later phase preferentially formed at lower TetCP/PVPA ratios while the amount of HAp increased with increasing TetCP/PVPA ratio. The reactions appear to start with the softening of the polymer when heated to T > Tg. The flowing polymer surrounds the TetCP grains permitting the TetCP to initially form DCPA crystallites in a matrix of the Ca salt of the polymer. When H2O is added prior to pressing, the DCPA produced reacts with the remaining TetCP forming HAp.

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Composites of calcium phosphates and the calcium salt of a biomedical polymer were prepared in situ by hot-pressing particulate mixtures of poly (vinyl phosphonic acid) (PVPA) and tetracalcium phosphate Ca4(PO4)2O, or TetCP) at different temperatures, pressures, and time periods. The objective was to establish whether PVPA could react with TetCP (Ca/P ratio of 2.0) to form a calcium salt, and thereby decrease the available Ca/P ratio 1.67 to facilitate hydroxyapatite (Ca10(PO4)6(OH)2 or HAp) formation. The effects of varying the bulk composition, temperature (to 300 degrees C), pressure (to 690 MPa) and time (to 60 min) on the reaction between TetCP and PVPA were studied using X-ray diffraction, infra-red spectroscopy and scanning electron microscopy techniques. Results showed that the conversion of TetCP into HAp increased with compaction time as temperature and/or pressure were increased. Formation of anhydrous dicalcium phosphate (CaHPO4, or DCPA) was also observed. Complete conversion of TetCP to HAp was achieved in composites pressed at 250 degrees C and 415 MPa for 30 min.

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The effect of bioactive glass on the mechanical properties of hydroxyapatite-Ca polyacrylate composites was studied. Powder mixtures of tetracalcium phosphate (TetCP), poly(acrylic-co-itaconic) and bioactive glass (up to 50% by weight) were hot pressed for 30 min at 300 degrees C and 40 kpsi. Tensile strengths, elastic moduli, and microstructures of the composites produced were investigated. Results showed the mechanical properties of these composites were enhanced by the addition of bioactive glass. The highest values of tensile strength and elastic modulus were achieved with the addition of 10% bioactive glass. Composites were immersed in SBF for up to 10 days, then in 1.5 simulated body fluid (SBF) for a week. The changes in the concentrations of Ca, P, and Si ions of these solutions were measured. The microstructures of these composites after SBF immersion were also evaluated. Concentrations of Ca, P, and Si increased with the time of immersion in SBF owing to the formation of an apatite layer on their surfaces as found by SEM with energy-dispersive spectroscopy attachment.

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Hydroxyapatite-biodegradable polymer composites have been formed by a low temperature chemical route. Precomposite structures were prepared by combining alpha-Ca(3)(PO(4))(2) (alpha-tricalcium phosphate or alpha-TCP) with poly(L-lactic) acid and poly(DL-lactide-co-glycolide) copolymers. The final composite structure was achieved by in situ hydrolysis of alpha-TCP to Ca(9)(HPO(4))(PO(4))(5)OH (calcium deficient hydroxyapatite or CDHAp) either in solvent cast or pressed precomposites. Hydrolysis was performed at 56 degrees C-a temperature slightly above the glass transition of the polymers. The effects of polymer chemistry, composite formation technique, and porosity on hydrolysis kinetics and degree of transformation were examined with isothermal calorimetry, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy. Calorimetric data and XRD analyses revealed that hydrolysis reactions were inhibited in the presence of the polymers. Isothermal calorimetry indicated the extent of the alpha-TCP to CDHAp transformation in 24 h to be 85% in the solvent cast composites containing PLGA (85:15) copolymer; however, XRD analyses suggested almost complete reaction. The CDHAp formation extent was 26% for the pressed composites containing the same polymer. In the presence of NaCl as a pore generator, 81% transformation was observed for the pressed composites. This transformation occurred without any chemical reaction between the polymer-inorganic components, as determined by Fourier transform infrared spectroscopy. Minimal transformation to CDHAp occurred in composites containing poly(L-lactic) acid.

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The microstructural and mechanical properties of composites composed of calcium deficient hydroxyapatite (CDHAp) and poly(lactide-co-glycolide) (PLGA) have been investigated. The composites were formed by hydrolysis of alpha-tricalcium phosphate (alpha-TCP) to CDHAp in pressed precomposite compacts of alpha-TCP-PLGA-NaCl. The differences in hydrolysis of alpha-TCP-PLGA-NaCl for two compositions of 80:10:10 wt % and 60:20:20 wt %. were monitored by isothermal calorimetry and X-ray diffraction. The microstructural evolution and variance in final composite microstructure after hydrolysis at 37 degrees C, 45 degrees C, and 56 degrees C were examined by scanning electron microscopy. HAp-PLGA composite formed from the alpha-TCP-PLGA-NaCl (80:10:10) precomposites at 37 degrees C developed a tensile strength of 13.3 +/- 0.9 MPa, a flexural strength of 24.8 +/- 1.7 MPa, and Young's modulus of 2.8 +/- 0.3 GPa. These values were 12.00 +/- 0.2 MPa, 36.1 +/- 2.1 MPa, and 5.5 +/- 0.8 GPa for the precomposite composition 60:20:20. All these mechanical properties showed a variation with hydrolysis temperature and composition. The differences in mechanical properties were related to the final microstructures of the composites, which are governed by the morphological changes in the polymer structure at its glass transition temperature and the extent of cement-type formation of CDHAp by hydrolysis of alpha-TCP.

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A hot-pressing technique was used to prepare composites anticipated to be biocompatible. Ca(4)(PO(4))(2)O (TetCP) was reacted with an acrylic-itaconic copolymer (CoP) in the absence of a solvent to form composites comprised of Ca(10)(PO(4))(6)(OH)(2') (hydroxyapatite, or HAp) and the Ca polyalkenoate salt. The effect of temperature, pressure, and hot-pressing time on the mechanical properties and microstructure of the composites were studied. Results showed that both tensile strength and elastic modulus increased when temperature and time were increased. When the compaction pressure was increased, these properties initially increased but decreased at high pressures. These variations in the mechanical properties were correlated with the microstructure of these composites. The mechanism of the reaction was also studied. Reaction starts when the copolymer is heated to above its T(g) permitting it to flow and react with the TetCP grains. The COOH groups on the polymer are neutralized by Ca(2+) ions liberated from the TetCP. At the end of reaction, a network of the Ca polyalkenoate salt is formed in which HAp crystals are embedded.

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Development of a new program for diagnosis and treatment of spine-related problems provided a unique opportunity to design and implement a new model for delivery of health care incorporating outcomes measurement and improvement. Key features include: application of microsystem thinking and interdisciplinary practice; integration of a uniform outcomes measurement tool, the Dartmouth Clinical Value Compass; and touch pad technology for data collection. This, for the first time, provided clinically meaningful point-of-service data and aggregated information for improvement. A further advantage was the ability to integrate a clinical research program within this microsystem. A multisite clinical research trial, the Spine Patient Outcomes Research Trial (SPORT), modeled on the Spine Center microsystem and funded by The National Institute of Arthritis, Musculoskeletal and Skin Diseases and the Office of Research on Woman's Health, the National Institutes of Health, and the National Institute of Occupational Safety and Health, the Centers for Disease Control and Prevention, is currently underway. The significant problems we face today cannot be solved by the same level of thinking that created them.

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Changes in hematological and serum biochemistry parameters in female zinc (Zn)-dosed farm-raised mallards (Anas platyrhynchos) fed four different diets were examined. Sixty ducks received an average dose of 0.97 g of Zn in the form of eight, 3.30-mm diameter shot pellets containing 98% Zn and 2% tin, and another 60 ducks were sham-dosed as controls. Fifteen ducks from each of the two dosing groups were assigned to one of four dietary treatments: corn only, corn with soil, commercial duck ration only, or commercial duck ration with soil. Shot-pellet dissolution rates ranged from 7 mg/Zn/day to 27 mg/Zn/day. Regardless of diet, the Zn dose resulted in mortality; incoordination; paralysis and anorexia; decreased body, liver, pancreas, gonad, and gizzard weight; increased kidney weight; and macroscopic lesions. Zn-dosed ducks had a lower mean erythrocyte packed cell volume (PCV), higher mean reticulocyte count, and a greater number of individuals with immature and/or abnormal erythrocytes, than did control mallards. Mean total leucocyte counts were higher in Zn-dosed ducks than in controls. Zn-dosed ducks that had soil available had higher leucocyte counts than those without soil. Zn-dosed ducks were characterized by a marked heterophilia and relative lymphopenia. In Zn-dosed ducks, the mean lymphocyte count was highest in those provided a commercial duck ration, and lowest in those fed corn. In control ducks, the mean lymphocyte count was highest in ducks fed corn, and lowest in those provided soil along with a commercial duck ration. Zn-dosed mallards had higher serum aspartate aminotransferase and amylase levels, and lower alkaline phosphatase activities than control ducks. Serum phosphorus and uric acid concentrations were higher, and calcium, glucose, and total protein levels lower, in Zn-dosed ducks than in control ducks. Diet did affect serum calcium, phosphorus, total protein, and uric acid concentrations. Differences in erythrocyte and leucocyte parameters, serum enzyme activities, and metabolite concentrations were associated with dose and diet effects. Diets high in protein and other organic matter and calcium and phosphorus did not prevent or substantially alleviate Zn toxicosis in farm-raised mallard ducks.

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The kinetics of hydroxyapatite (HAp) formation by direct hydrolysis of alpha-tricalcium phosphate (alpha-TCP) [alpha-Ca(3)(PO(4))(2)] have been investigated. Transformation kinetics were examined for reactions at 37 degrees C, 45 degrees C and 56 degrees C by isothermal calorimetric analysis. Setting times and morphologies of the resultant HAp were found to be strongly dependent on reaction temperature. XRD analysis accompanied by FTIR confirmed that phase pure calcium-deficient hydroxyapatite (CDHAp) [Ca(10-x)(HPO(4))(x)(PO(4))(6-x)(OH)(2-x)] was formed. Complete reaction occurs within 18, 11, 6.5 h at 37, 45 and 56 degrees C, respectively. The extent of HAp formation differs for particulate slurries and pre-shaped forms of reactant alpha-TCP. Formation of hydroxyapatite in pre-formed pellets was hindered due to limited water penetration, but enhanced with the presence of NaCl as a pore generator. Regardless of the precursor characteristics and temperature, HAp formation is characterized by an initial period of wetting of the alpha-TCP precursor, an induction period and a growth period during which the bulk transformation to HAp occurs. The microstructures of the resultant HAp at all temperatures were generally similar and are characterized by the formation porous flake-like morphology. Microstructural coarsening was observed for the CDHAp formed above the physiological temperature. The hardening generated by the hydrolysis reaction was demonstrated using diametrical compression tests. The original tensile strength of 56% dense alpha-TCP increased from 0.70+/-0.1 MPa to 9.36+/-0.4 MPa after hydrolysis to CDHAp at 37 degrees C, corresponding to a density of 70%.