Evidence of calcium phosphate depositions in stenotic arteriovenous fistulas.

This study investigates vascular samples from patients with and without end-stage renal disease (ESRD) to determine the occurrence of calcium depositions. Findings in stenotic arteriovenous (AV)-fistula veins were compared with those of nonstenotic AV-fistula veins, non-AV-fistula veins, and atherosclerotic vessels. Calcium and phosphorus content was measured by means of scanning electron microscopy and its built-in method of energy-dispersive spectrometry (EDS) X-ray analysis. We found calcium and phosphorus in samples from AV fistulas with stenotic areas with a calcium/phosphorus molar ratio of 1. Based on EDS analysis and crystal shape comparison, we conclude that calcium phosphate precipitations in stenotic AV fistulas are brushites with the composition CaHPO(4)*2H(2)O. This specific calcium phosphate deposition was found solely in stenotic AV fistulas, not in nonstenotic AV-fistula veins or non-AV-fistula veins regardless of whether the patient had ESRD. Moreover, this calcium phosphate deposition was different from calcium compounds found in atherosclerotic samples. Whether the precipitation of brushite is primarily involved in the development of vascular-access stenosis or represents a secondary consequence cannot be determined from the present study.