Case 9 - That’s how it flows, or not...
Author: Nish Cherian Reviewer: Nick Mani
A 60-year old female presents to a small rural ED with shortness of breath and mild chest pain. She has a small O2 requirement and tachycardic at 108bpm. She denies any calf pain, though her left calf is mildly tender on examination. CXR appears normal and ECG shows no obvious ischaemia.
Her echo windows are a bit tricky to obtain. You also elect to perform a 3-point DVT scan to aid your clinical diagnosis.
PLAX - no gross LV impairment
A4C (off axis) - slightly dilated RV with abnormal septal movement into the LV
Subcostal view
Common femoral vein (CFV) at saphenofemoral junctioni (SFJ)
(Superficial) Femoral vein distal to SFJ (at level of bifurcation of superficial and deep branches)
(Superficial) Femoral vein at mid-thigh level
Popliteal vein (PV) at trifurcation - dilated and non-compressible with hyperechoic occlusive thrombus within
Popliteal vein at trifurcation with Colour Doppler - showing lack of flow within occluded PV and pulsatile flow in PA below
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Dilated RV - normal RV/LV ratio is about 0.6-0.7, however a ratio of 1 or more is more sensitive to suggest RV strain (tip: the RV occupies more of the apex as it enlarges)
Bowing of the septum into the LV (on A4C) and flattening of septum on PSAX (“D-sign”)
Dilated IVC (in conjunction with the above) - suggests upstream obstruction
Reduced TAPSE (tricuspid annular plane systolic excursion) <16mm - suggestive of reduced RV longitudinal function
McConnell’s sign - RV free wall hypokinesis/dyskinesis with sparing of apical wall
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Common femoral vein - proximal, at the level of and distal to SFJ
(Superficial) Femoral vein - good practice to scan up to mid-thigh level at least
Popliteal vein - proximal and at level of trifurcation
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Collapse of the venous walls against each other on compression with the transducer - normally there should be complete coaptation
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Lack of compressibility - this is the primary mode of diagnosing a DVT in compression ultrasonography and has high sensitivity and specificity.
Direct visualisation of the clot, whilst specific, is not always possible (depending on the age of clot) - acute thrombi are usually hyperechoic but may sometimes be iso- or anechoic.
Colour Doppler is also helpful in determining if a clot is occlusive or not - this is usually used with “augmentation” of venous flow by squeezing the leg distal to where you are scanning and looking for a homogenous increase in venous flow.
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Positioning:
Frog’s leg positioning (externally rotate and bend knee - sometimes helpful to place a pillow under the thigh for support/comfort.
Slight head elevation to 30 degrees can help with visualisation of vein
Machine:
Linear transducer - venous preset if available
If larger patients, can use curvilinear transducer (may need to use the higher frequency bandwidth eg. Res mode)
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Lymph nodes - can appear similar as hypoechoic oval structure with hyperechoic centre (tip: rotate into long axis, lymph nodes will look the same as oval shaped)
Baker’s cyst - may be mistaken for popliteal thrombus (usually anechoic with defined borders in both transverse and longitudinal)
Superficial thrombophlebitis - superficial veins do not accompany arteries whilst the deep veins do
Groin haematomas - also well-circumscribed in long and short-axis
Case resolution
The patient had some equivocal findings on echo but POCUS of the deep veins helped to facilitate a diagnosis. She was treated with low-molecular weight heparin and subsequently underwent a CTPA which confirmed a saddle PE (unfortunately the pulmonary trunk in the parasternal window was not clearly visualised on ultrasound). She remained haemodynamically stable and was transferred to the local referral hospital for ongoing management and monitoring.
