LIMB ULTRASOUND IMAGING


Used to help diagnose sprains, strains, tears, and other soft tissue conditions.

WHY IS THE PROCEDURE PERFORMED?

  • When a patient presents with leg pain and swelling, there are two main causes:

  • blood clot (thrombus) in a deep vain: deep vain trombosis DVT

  • Burst knee joint space with extravasation of synovial fluid into the surrounding soft tissue: Baker's Cyst.

  • Confusing masses such as abscesses, hepatomas, tumours in the knee joints or other parts of the limb.

  • Infections in the limb can be distinguished: if draining is needed, if it is cellulitis, if it acute osteomyelitis.

  • Examination of traumatic limb injuries: tendon problems, distinction between tendon breaks and bruises.

  • Detection of foreign bodies in the hands or feet.

  • Muscle tears and muscle injuries

LENGTH OF THE PROCEDURE

15 to 30 minutes.

BASICS

IDENTIFIYING MUSCLES

They can be individually visualised by the alignment of muscle fibres. Muscles are separated by an echogenic line resulting from connective tissue. When the limb moves, the muscles move and the individual muscle groups can be distinguished.

IDENTIFYING BONES

They reflect almost the entire ultrasound beam, so only their surface can be seen.

IDENTIFYING TENDONS

They have a distinct structure: two echogenic lines outline a series of strongly echogenic linear structures.

Deep vain thrombosis:

Extrinsic compression manoeuvres: compressing the vein with the transducer in a transverse position to see whether it changes.

During compression the normal vein walls will touch; this is called coaptation of the vessel walls. A vein is normal when both the anterior and posterior walls though. If there is a clot within the vein, it will not compress when pressure is applied. If the vein walls completely compress, this rules out the presence of a clot at that site.

Popliteal Fossa Cyst (Baker’s Cyst)

  • Anechoic cystic mass in popliteal fossa

  • May have linear echogenic septations or low-level

echoes

  • May extend into calf region

  • Should not be mistaken for popliteal artery

aneurysm

Popliteal Artery Aneurysm

  • Focal dilation of popliteal artery

  • Pulsatile on real-time imaging

  • May contain low-level echoes (clots)

  • Walls may be echogenic because of calcification

  • Flow seen within vessel on colour Doppler

Calf Hematomas and Abscesses

  • Cystic, solid, or complex mass within muscle

  • Localized anechoic fluid collection within muscle

  • Variable appearance

Cellulitis

  • Diffuse thickening of soft tissues

  • Tissue borders with increased echogenicity

  • Increased vascularity within tissue on colour Doppler

Pseudoaneurysms

  • May develop after penetrating trauma or arterial catheterization

  • Saccular anechoic mass adjacent to the femoral artery

  • Flow seen within mass

  • Compression with transducer pressure often used to promote clotting

Foreign Bodies

  • Glass, metal, and plastic are sometimes localized in extremities.

  • Foreign bodies are seen as echogenic foci with posterior shadowing.

  • Metal and glass are more echogenic than wood or plastic.

Sources:

Clinical sonography, Roger C. Sanders, Tom C. Winter

#ultrasound #imaging

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