In various examples, a medical device is configured to be at least partially insertable within a patient. The medical device includes a first elongate member including a sidewall surrounding and defining a lumen extending through the first elongate member between a first proximal end and a first distal end. A second elongate member is sized and shaped to fit within the lumen of the first elongate member. A coil is disposed within the sidewall of the first elongate member, wherein the coil is configured to sense a position of the second elongate member with respect to the coil. In some examples, the first elongate member includes a catheter, and the second elongate member includes a guidewire.