Beyond the 10-year barrier: ultrastructural insights into long-term tunneled catheter function from calcified specimens-a report on 4 cases.

Tunneled-cuffed catheters (TCCs) remain a primary vascular access modality for patients requiring maintenance hemodialysis, yet catheter dysfunction is a frequent and challenging complication. Although the factors contributing to catheter dysfunction are well recognized, the ultrastructural changes of fibrin sheaths in long-term indwelling catheters have not been systematically documented in the literature. Herein, we present 4 cases of malfunctioning subcutaneous TCCs of varying dwelling durations. Catheter exchange was performed under digital subtraction angiography guidance, and fibrin sheath specimens were collected for analysis. Ultrastructural assessment was conducted via scanning electron microscopy, supplemented with energy-dispersive X-ray spectroscopy and hematoxylin-eosin staining. Fibrous tissue hyperplasia was observed in all 4 specimens. Specimens from the 2 catheters with longer dwelling durations exhibited myofiber degeneration within the fibrin sheaths, accompanied by tissue calcification. In contrast, fibrin sheaths from the 2 catheters with shorter dwelling durations were predominantly characterized by exudates and inflammatory cellular infiltration. Fibrin sheath hyperplasia is a consistent pathological feature in long-term hemodialysis catheters. These findings suggest that prolonged catheter dwelling time correlates with progressively more severe pathological changes in the fibrin sheath.