A first catheter can include a first catheter body providing a longitudinal bore and can have flexible first seal at its distal portion. The first seal can at least partially occlude the bore at the distal portion of the catheter body in a first configuration. A second catheter can be slid into or through the bore of the first catheter body, such as to expand the first seal into a second configuration. Wicking or reflux can be inhibited. Other features, applications, and methods can be included.
