In some examples, an introducer apparatus includes an outer elongated member defining a lumen extending therethrough, the lumen having a lumen dimension in cross-section, and a dilator configured to be received within the lumen of the outer elongated member, the dilator may comprise a proximal section, a distal section comprising a distal end of the dilator, and an intermediate section disposed between the proximal section and the tapered distal section. In some examples, the intermediate section may define a through-opening that configures the intermediate section to be collapsible from an expanded configuration to a collapsed configuration. In the collapsed configuration, the intermediate section may have a first dilator dimension in cross-section that is less than a second dilator dimension in cross-section when the intermediate section is in the expanded configuration.