Devices and methods are provided for sealing a catheter insertion site to maintain sterility. In one embodiment, a catheter dressing is provided that includes an adhesive plate configured for attachment to the skin of a patient and a flexible sheath that extends proximally from the adhesive plate. The sheath can be capable of longitudinal extension from a compressed to an extended state and can be configured in its extended state to surround an external segment of a catheter implanted in the patient and circumferentially seal to a portion of the external segment at a distance from the adhesive plate. The dressing can also be configured to restrict longitudinal movement of the catheter while at the same time permitting non-longitudinal movement. One-piece rigid or semi-rigid dressing bodies are also disclosed, as are various methods and devices for facilitating removal and or replacement of a catheter dressing.