Brief Communication Histologic Development of the Sheath That Forms Around Long-Term Implanted Central Venous Catheters

ABSTRACT. Background: Chronically implanted catheters often become covered with a thin, white adherent covering of tissue that has been referred to as a fibrin sheath. This tissue often in-terferes with catheter function. Methods: To chronicle the devel-opment of this sheath, rats were implanted with silicone rubber central venous catheters. Five rats were euthanized at 3, 7, and 60 days postimplantation so that gross necropsy and histology could be performed on the catheterized vessels. Results: The coat-ing that developed around the external portion of the catheter started as a dark red thrombus containing fibrin and progressed into vascularized, fibrous connective tissue. Conclusions: The translucent to white sheath that forms around chronically im-planted catheters is not composed of fibrin and is therefore not likely to be dissolved by fibrinolytic agents such as urokinase, streptokinase, or tissue plasminogen activator. (Journal of Parenteral and Enteral Nutrition 20:156-158, 1996) Chronically implanted central venous catheters (CVCs) often develop a layer of thin, adherent tissue. When it cov-ers the tip, this material can cause withdrawal occlusion and sometimes interferes with infusion through the cath-eter. This covering has been widely referred to as a fibrin sheath. 1-7 However, during histologic examination of veins from rats with occluded CVCs, we noted that this cover-ing was not composed of fibrin. The present study was undertaken to investigate and describe the development of this tissue covering during the course of 8 weeks in rats with CVCs inserted through the right external jugular vein