Hemodialysis-Induced Renal Perfusion Decline: Unraveling the Pathophysiological Mechanisms Linking Intradialytic Circulatory Stress to Residual Renal Function Loss

Inclusion Criteria: * (1) adult patients with end-stage renal disease (ESRD) within 3 months of commencing HD; (2) preserved RRF defined as urinary output \>500 mL/24 h or eGFR ≥3 mL/min/1.73 m² Exclusion Criteria: * (1) known allergy to sulfur hexafluoride microbubbles (SonoVue®) microbubbles; (2) vascular access dysfunction; (3) combined peritoneal dialysis; (4)severe cardiopulmonary disease; (5) active infection or malignancy; (6) communicable diseases; (7) pregnancy or breastfeeding; (8) participation in other clinical trials.