What is the purpose of advancing the dilator and sheath over the guidewire during the Seldinger technique?

• A. To enlarge the tract and introduce the sheath for catheterization
• B. To secure the guidewire
• C. To visualize the vessel with ultrasound
• D. To remove the guidewire

Answer: (A)

Advancing the dilator and sheath over the guidewire serves to enlarge the puncture tract and create a stable conduit into the vessel for catheterization. The dilator gently widens the tissue and the vessel opening, reducing friction and trauma as the sheath passes through. The sheath then remains in place to provide a protected channel through which the catheter or device can be delivered, preserving access and helping prevent bleeding or hematoma. The guidewire stays in place during this step to maintain the correct entry path; removing it would end access. While ultrasound guidance and securing the wire are important in other parts of the procedure, the main purpose here is to dilate the tract and establish the working channel for catheter insertion.