Pre-existing venous structural remodeling and arteriovenous fistula maturation assessed by conventional histology and nonlinear optical microscopy

Arteriovenous fistula (AVF) nonmaturation remains a significant clinical challenge in hemodialysis patients. Pre-existing structural alterations of the venous wall, including fibrosis and extracellular matrix remodeling, may impair adaptive outward remodeling of the outflow vein after arterialization. Nonlinear optical microscopy techniques such as second-harmonic generation (SHG) enable collagen-sensitive visualization of tissue architecture and may provide additional structural information beyond conventional histology. This single-center observational study included two cohorts of patients undergoing vascular access surgery. Cohort A included patients undergoing AVF creation, with venous samples obtained before anastomosis to assess pre-existing structural features in relation to maturation outcome. Cohort B included patients undergoing revision or ligation of failed AVFs, providing specimens representing advanced remodeling. All samples were evaluated using hematoxylin and eosin staining and SHG microscopy. Fibrosis and SHG-derived parameters were assessed using semiquantitative scoring systems. A total of 76 patients were included. Histological fibrosis scores did not differ between matured and failed AVFs, whereas SHG microscopy revealed significant differences. Failed AVFs demonstrated higher collagen brightness, increased fibrillar disorganization, and reduced layer preservation compared with matured AVFs. These findings suggest that SHG-derived parameters may provide additional information on venous wall remodeling not detected by conventional histology.