A catheter proximal section is preferably formed from a relatively soft part and a relatively rigid part, and includes a proximal terminal end that defines a perimeter of an opening into a lumen of the catheter. The proximal section may further include a feature for interlocking engagement with an accessory tool. An inner surface of each of the relatively soft and rigid parts may be located opposite one another, on either side of the catheter lumen. The relatively soft and rigid parts may be included in a sealing assembly that further includes an attachment feature for removable connection of the assembly to the proximal section catheter.