This prospective, multicenter study demonstrates that access inflow stenosis occurs in one third of the cases referred to interventional facilities with clinical evidence of venous stenosis or thrombosis. This is much higher than has been traditionally reported.

These results demonstrate that an organized approach based upon a comprehensive program utilizing VA counseling, VM, application of full range of surgical techniques, and salvage procedures can be very successful in providing optimum vascular access to the catheter-dependent patient.

Surgical creation of new anastomosis has been proposed as the preferred treatment for perianastomotic stenoses of fistulae. However, disadvantages of surgical approach have included (1) frequent conversion of fistula to a graft by using synthetic graft material to create a new anastomosis, (2) shortening the length of the cannulation segment by proximal autologous arteriovenous neoanastomosis, and (3) abandoning the fistula altogether in favor of a synthetic graft. We report the results of a prospective study using percutaneous balloon angioplasty (PTA) to treat fistulae with perianastomotic lesions. Seventy-three consecutive patients undergoing 112 PTA procedures for the treatment of perianastomotic lesions were studied. Primary and secondary patency rates were calculated. Procedure success, procedure-related complications, and conversion of fistulae to grafts were recorded. The initial success rate was 97%. The degree of stenosis before and after PTA was 81 +/- 9 and 11+/-11%, respectively. Primary patency rates at 6, 12, and 18 months were 75, 51, and 41%, respectively. Secondary patency rates at 6, 12, and 18 months were 94, 90, and 90%, respectively. Grade I hematoma occurred in three and vein rupture in two cases. No grafts were inserted. These outcomes are superior to those that have been reported for surgery. The outpatient PTA is safe and effective for the management of perianastomotic stenosis. Because of its advantage of fistula preservation, the percutaneous approach should be considered as the preferred first-line therapy for the management of perianastomotic fistula lesions.

Venous mapping using venography has been considered to be the gold standard for identifying veins suitable for arteriovenous fistula (AVF) creation. By utilizing a radiocontrast medium, however, venography introduces the risk of radiocontrast-induced nephropathy. The risk of this complication in the chronic kidney disease (CKD) population has not been previously studied. Twenty-five consecutive patients (CKD stage 4 and 5) undergoing venography were enrolled in this study. Patients were advised not to fast for the procedure and were encouraged to take oral fluids. Radiocontrast-induced nephropathy was defined as a 20% decrease in the estimated glomerular filtration rate (GFR) from the baseline value at 48 hours after contrast administration. Weekly telephone calls were made for a total of 4 weeks to assess the need for dialysis. Venography was performed by interventional nephrology using 10-20 cc of low osmolarity contrast medium. Data were collected prospectively. Median age was 48.9 +/- 7.8 years and 52% of the patients had diabetes. Complete sets of pre- and postprocedure GFRs were available in 21 patients. At 48 hours, there were no differences between the pre- and postprocedure GFRs. At the third week, one patient developed flu-like symptoms with severe gastroenteritis and was hospitalized for volume depletion. This patient initiated dialysis during the hospital stay. We conclude that at 48 hours, our cohort did not develop radiocontrast-induced nephropathy. During the 4-week phone call follow-up, only one patient needed dialysis. Large-scale studies with a longer follow-up using GFR estimation are needed to confirm these preliminary findings.

Mesangial cells, a combined smooth muscle- and fibroblast-like phenotype, are important regulators of renal function. These cells exist in a region of variable osmolarity and may require Cl^– channels for volume regulation. Additionally, Ca²⁺-activated Cl^– channels in these cells may participate in Ca²⁺-dependent contractile responses to vasoactive agonists. Relatively little, however, is known about mesangial cell Cl^– currents (I_Cl); including the biophysical description and pharmacological characterization. We used whole-cell patch clamp to study I_Cl in cultured human and SV40-transformed murine mesangial cells. I_Cl was measured in cells dialyzed and bathed with symmetrical N-methyl-D-glucamine chloride solutions to minimize cation currents. Dialysis with buffers to control intracellular Ca²⁺ ([Ca²⁺]_i), extracellular solutions of varied osmolarity, and manipulation of the transmembrane Cl^– gradient were used to separate two currents: I_Cl.vol (volume-sensitive), and I_Cl.Ca (Ca²⁺-activated). In symmetrical Cl^– with low [Ca²⁺]_i, I_Cl.vol was outwardly rectifying and modulated by osmolarity. I_Cl.vol demonstrated slight time- and voltage-dependent inactivation. In symmetrical Cl^– with elevated [Ca²⁺]_i and hypertonic bath, I_Cl.Ca was linear, but in asymmetrical Cl^– (low [Cl^–]_i) was outwardly rectifying and demonstrated time- and voltage-dependent activation. Permeability sequences for both I_Cl.vol and I_Cl.Ca were I^– > Br^– > Cl^– > F^–; however, there were differences in the relative magnitudes. Tamoxifen inhibited I_Cl.vol more potently than I_Cl.Ca, whereas niflumic acid inhibited I_Cl.Ca more potently than I_Cl.vol. We have separated and characterized two types of I_Cl in cultured human and murine mesangial cells. I_Cl.Ca and I_Cl.vol have different biophysical and pharmacological characteristics. These observations on I_Cl.Ca and I_Cl.vol may provide insight into mesangial cell reactivity and volume regulation.