Access & devices
Access needle
The device used to make the initial percutaneous entry into a vessel, duct or space under image guidance, before a guidewire is passed through it.
- Owner
- WIRS education committee
Overview
An access needle is a short, rigid or semi-rigid hollow needle used to puncture the skin and advance to a target vessel, duct or collection under ultrasound, fluoroscopic or CT guidance. Access needles are broadly single-wall or double-wall (Seldinger-type) in design: a single-wall needle is advanced until only the near wall of the target is crossed, while a double-wall needle is deliberately advanced through both walls and then withdrawn until flow is seen — a technique used less often now that direct, image-guided single-wall puncture is standard for most vascular access. Correct positioning is confirmed before a guidewire is ever passed — commonly by free flow or aspiration of blood, bile, urine or fluid, by image guidance, or by both.
Sizing and compatibility
- Needle size is described by gauge (a lower gauge number means a larger bore), not by the French scale used for sheaths and catheters.
- The needle's inner bore must accommodate the outer diameter of the guidewire chosen to pass through it — the first link in the sizing chain that continues through the sheath and catheter.