MORPHOLOGICAL CHANGES IN THE ZONE OF ARTERIOVENOUS ANASTOMOSIS IN FORMATION OF PERMANENT VASCULAR ACCESS FOR HEMODIALYSIS

Background. Importance of the problem of long-functioning vascular access for program hemodialysis. Thrombosis of arteriovenous fistula leads to repeated operations and creates additional problems in hemodialysis procedure. Aim. To study peculiarities of morphological picture in patients with thrombosis of arteriovenous fistula. Materials and Methods. The study included 35 patients diagnosed with 5 degree chronic kidney disease (CKD-5) who were receiving replacement therapy for more than 1 year. All the patients underwent three and more reconstructions due to thrombosis or critical stenosis of arteriovenous anastomosis. Diseases that led to renal failure were: glomerulonephritis in 15 (43%) patients, essential hypertension in 10 (28%) patients, diabetes mellitus in 5 (14%) patients, and polycystic kidney in 1 (4%) patient. Fragments of thrombosed fistulae were sent to histologic examination. Fixation was done in 10% neutral formalin solution. The tissue material was subject to standard histological preparation. Specimens were stained with hematoxylin and eosin by Mallory method. Results. Most of the removed arteriovenous fistulae showed identical changes: desquamation of endothelial lining, hyperplasia of t.intima due to overgrowth of connective tissue with the structure corresponding to that of cribriform dense connective tissue. Because of this peculiarity, it was impossible in most cases to determine a distinct boundary between the internal layer of the vessel and t.media. Due to desquamation of the epithelium, the internal surface of the vessel became a starting point for formation of parietal thrombus. Most organized thrombi had channels with fragments of endothelial lining that evidenced recanalization processes in the fistula. However, the ‘throughput' capacity of these channels was insufficient to compensate for the blood flow through the vessel. The structure of t.media also changed. There were noted edema, dyscomplexation of the smooth muscle component due to growth of the elements of the cribriform connective tissue between the leiomyocytes. The external layer was represented by fibrous connective tissue with different extent of ordering. Vasa vasorum was noted. No special changes were found associated with the disease that led the patient to the CKD, with duration of thrombosis and with the number of previous operations. Conclusion. The main cause of thrombosis of arteriovenous fistula was overgrowth of connective tissue in intima. This morphological picture was characteristic of all the examined patients irrespective of the disease which provoked chronic renal failure.