Vascular Anatomy for Ultrasound-Guided Access: Upper Extremity and Neck

Successful ultrasound-guided vascular access depends on recognizing target vessels by their anatomic relationships, echographic characteristics, and response to probe compression. Clinicians who understand the anatomy before picking up the probe identify target vessels faster, avoid inadvertent arterial cannulation, and achieve higher first-attempt success rates.

Parent guide: Ultrasound-Guided Vascular Access: Complete Reference

Ultrasound Basics: Identifying Vessels

The Compressibility Test

The single most reliable bedside test for distinguishing vein from artery:

• Apply gentle downward pressure with the ultrasound probe
• Vein: Collapses completely with gentle pressure (venous walls are thin, low-pressure)
• Artery: Remains round and resists compression (arterial walls are thick, high-pressure)

Clinical application: Before advancing any needle toward a vessel, confirm compressibility. If the structure does not collapse with gentle pressure, it is an artery — do not advance the needle into it.

Additional Differentiating Features

Echogenicity of Structures

Anechoic (black): Fluid-filled structures — blood vessels, fluid collections. All vessels appear dark/black on B-mode ultrasound.

Hyperechoic (bright white): Dense structures — bone, calcifications, dense fascia.

Hyperechoic ring: Arteries often appear with a brighter outer wall (muscular media) compared to veins (thin intima-media complex).

Nerve fascicles: Nerves appear as round or oval structures with a “honeycomb” internal pattern of alternating bright and dark fascicles — distinct from the smooth dark appearance of vessel lumens.

Upper Extremity Venous Anatomy (PICC and PIV Territory)

Basilic Vein

Anatomy: Originates on the medial aspect of the dorsal hand venous network, travels up the medial forearm as the basilic vein, passes through the medial antecubital fossa, and continues as the medial upper arm basilic vein. At the mid-upper arm, it pierces the deep fascia and joins the brachial vein to form the axillary vein.

Relationship to brachial neurovascular bundle: In the upper arm, the basilic vein lies medially — typically just medial or slightly posterior to the brachial artery. The medial cutaneous nerve of the forearm and medial cutaneous nerve of the arm run in proximity.

Ultrasound identification: Typically found at a depth of 0.5–2.5 cm in the medial upper arm. Compresses easily. Larger than the brachial or cephalic veins in most patients.

Why preferred for PICC: The basilic vein is the largest vein in the upper arm, has the most direct path to the axillary vein and SVC (without the tortuous path of the cephalic vein), and is accessible in the mid-upper arm away from the antecubital flexion area.

Brachial Vein

Anatomy: Two brachial veins (venae comitantes) run alongside the brachial artery in the medial upper arm. They merge variably, sometimes appearing as a single vein or as two flanking the artery.

Ultrasound identification: The brachial veins appear as paired dark circles flanking the brachial artery on transverse US. The artery is identified by pulsatility and non-compressibility; the paired veins compress with probe pressure.

For PICC: Brachial veins are acceptable PICC insertion vessels, though their smaller caliber (relative to basilic) increases catheter-to-vein ratio risk. If basilic vein is unavailable or too small (<3 mm), brachial vein is the secondary choice.

Caution: The brachial artery (in direct proximity) and the median nerve (which runs between or anterior to the brachial veins) require careful needle-path planning to avoid inadvertent arterial puncture or nerve injury.

Cephalic Vein

Anatomy: Travels along the lateral forearm and lateral upper arm. Enters the deltopectoral groove between the deltoid and pectoralis major muscles. Ultimately joins the axillary vein via the deltopectoral groove.

Ultrasound identification: Found laterally in the upper arm; relatively superficial. Appears similar to basilic vein but in lateral position.

For PICC: Less preferred. The cephalic vein has a tortuous path at the deltopectoral groove — a sharp angle where it joins the axillary vein. PICC catheters frequently fail to navigate this angle, resulting in proximal malposition. The insertion success rate via the cephalic vein is lower than via the basilic vein.

When basilic and brachial are unavailable, the cephalic is the last-choice upper arm PICC site.

Antecubital Fossa Veins

Median cubital vein: Connects the cephalic and basilic veins across the antecubital fossa. Often the most visible peripheral IV site. Not preferred for PICC insertion (lies directly over the elbow flexion point; catheter movement risk with elbow flexion).

Median antebrachial vein: Variable anatomy; runs in the central forearm. May be used for PIV access; rarely for PICC.

Neck Anatomy (IJ CVC Territory)

Internal Jugular Vein (IJ)

Anatomy: The IJ vein exits the skull at the jugular foramen, runs within the carotid sheath adjacent to the internal carotid artery (proximally) and the common carotid artery (distally), and descends in the neck to merge with the subclavian vein at the sternoclavicular junction, forming the brachiocephalic vein.

Relationships:

• Lateral to the carotid artery (in most patients) at mid-neck level
• Covered by the sternocleidomastoid (SCM) muscle at the lateral border of the SCM
• Runs posterior to the SCM at the medial border
• The vagus nerve runs between the IJ and carotid artery within the carotid sheath

Ultrasound identification:

• Transverse view: IJ appears as a large oval or round structure lateral to the round carotid artery
• IJ collapses with probe pressure; carotid does not
• Valsalva maneuver distends the IJ, making it more visible
• Patient head turned 30–45° contralateral

Anatomic variations: In approximately 5% of patients, the IJ runs medial to the carotid. Always confirm compressibility before cannulation.

Why preferred for US-guided CVC: The IJ is the most reliably accessible vessel for ultrasound-guided central access — it is superficial (2–3 cm deep), large, and easily identified and distinguished from the adjacent carotid artery.

Common Carotid Artery

Anatomy: Medial to the IJ in the lower neck; bifurcates into internal and external carotid arteries at the level of C4 (thyroid cartilage). Pulsatile on ultrasound; non-compressible.

Recognition: The carotid pulse is visible on the US screen as a pulsatile round structure that does not compress. Color Doppler shows high-velocity pulsatile arterial flow.

Relevance: Accidental carotid cannulation during IJ CVC insertion is the most serious IJ complication — especially if the dilator or catheter is advanced into the artery before recognition. US guidance reduces carotid cannulation rates from ~5% with landmark technique to <0.5%.

Femoral Anatomy (Femoral CVC Territory)

Femoral Vein

Location: Below the inguinal ligament in the femoral triangle; medial to the femoral artery.

Ultrasound identification (femoral triangle): Femoral artery and vein visible in the groin with patient in supine position. The vein is medial to the artery; the two vessels lie within the femoral sheath. The femoral nerve lies lateral to the artery.

NAVEL mnemonic (medial to lateral): Nerve, Artery, Vein, Empty space, Lymphatics.

For femoral CVC: Patient supine with leg slightly abducted and externally rotated. US identifies femoral vein medial to femoral artery; compressibility confirms venous nature.

Practical Scanning Tips

Vein augmentation (making veins more visible):

• Tourniquet application (for upper extremity) — increases venous filling
• Trendelenburg position — increases CVP and venous diameter
• Warming the extremity — increases venous caliber by vasodilation
• Fist pump (patient opens and closes hand) — increases basilic/brachial filling

Depth and gain settings:

• Set depth to 2–4 cm for upper arm veins (most are within 2 cm of skin surface)
• Adjust gain until vessels appear clearly dark against gray tissue background
• Too high gain: vessels may not appear dark (clutter from gain artifacts)
• Too low gain: vessels may be difficult to distinguish from surrounding tissue

Identifying the target before needling:

• Identify and confirm the target vessel in short-axis (transverse plane)
• Locate the vessel at the planned insertion site
• Plan the needle path: where will the needle enter, at what angle, to reach the center of the vessel

Related Resources

Related guides:

• Ultrasound Technique for Vascular Access
• Ultrasound for Peripheral IV Difficult Access

Related policies:

• Vascular Visualization Technology
• Vascular Access Site Preparation and Skin Antisepsis

References

1. Gorski LA, et al. (2021). INS Infusion Therapy Standards of Practice (Standards 22–25). J Infus Nurs, 44(Suppl 1).
2. Troianos CA, et al. (2011). Special articles: guidelines for performing ultrasound guided vascular cannulation. Anesth Analg, 114(1):46–72.
3. Brass P, et al. (2015). Ultrasound guidance versus anatomical landmarks for subclavian or femoral vein catheterization. Cochrane Database Syst Rev, (1):CD011447.
4. Egan G, et al. (2012). Sonographic assessment of the basilic vein for PICC. J Ultrasound Med, 31(11):1713–1718.