Medical devices, medical device systems, and methods for using the same are disclosed. An example medical device system may include a guide catheter having a proximal end, a distal end, and a lumen extending therebetween. The guide catheter may be designed to guide a therapeutic catheter to a target site. A guidewire may be disposed within the lumen of the guide catheter. The system may also include a trap balloon catheter including a catheter shaft and a balloon coupled to the catheter shaft. The trap balloon catheter may be designed to extend through the lumen of the guide catheter to a position adjacent to the distal end of the guide catheter. A trap balloon retainer may be coupled to the catheter shaft. The trap balloon retainer may be designed to prevent a distal end of the trap balloon catheter from extending distally beyond the distal end of the guide catheter.