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.
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.
They reflect almost the entire ultrasound beam, so only their surface can be seen.
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
May extend into calf region
Should not be mistaken for popliteal artery
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
Diffuse thickening of soft tissues
Tissue borders with increased echogenicity
Increased vascularity within tissue on colour Doppler
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
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.
Clinical sonography, Roger C. Sanders, Tom C. Winter