Abstract: A catheter designed for improved patency characteristics under forces normally exerted upon the catheter during use. The catheter features an inner wall having one or more protuberances running lengthwise in a manner parallel with the central axis of the catheter. The protuberances include a tip, a root defined along the inner wall, and a pair of sidewalls extending between the tip and the root. The roots of adjacent protuberances are spaced from one another. A fluid path is established between the inner wall and the opposed sidewalls of adjacent protuberances. The opposed sidewalls can be straight. Alternately, at least one of the opposed sidewalls includes a non-linear portion along its length. In response to a force normally exerted upon the catheter during use, the spacing between adjacent roots and, if so provided, the non-linear portion of an opposed sidewall prevents the opposed sidewalls from entering into total contact with one another, thereby preventing occlusion of the fluid path.