Introduction. Arteriovenous fistula is vital for patients with Stage 5 chronic kidney disease. Objective. To determine functional and morphological changes in the wall of an arterialized saphenous vein with a functioning arteriovenous fistula. Material and methods. A descriptive interventional study was conducted to identify anatomical changes occurring in the wall of the forearm saphenous vein with a functioning arteriovenous fistula. Results and discussion. The understanding of the remodeling processes that the vein undergoes, while being in the arterial circulation, is keying, as this knowledge will assist in improving the results and duration of arteriovenous fistula functioning. Even with the severely abnormal venous environment, the vein easily adapts to its new status, by changing the structure of the venous wall. Increasing the diameter is a key element in vein remodeling and makes it possible to predict whether the arteriovenous fistula will successfully function. There is an increase in the saphenous vein diameter in accord with the duration of hemodialysis through this arteriovenous fistula. Conclusion. The compensatory increase in the diameter of the saphenous vein during its arterialization is due to new hemodynamic conditions. The adaptive changes in the structure of the saphenous vein wall include compensatory plastic restructuring mainly due to the intima and partially the muscular layer; however, no complete compensation of the venous wall occurs; there is a process of collagenization of all venous wall layers.