Veins contain bicuspid valves, which are pocket shaped folds of the intima extending into the lumen of the vein. 1-3 pockets will form the valve.The opening of the pocket will point in the direction of blood flow ... towards the heart. Blood flowing toward the heart will flow through the pockets. If the flow reverses, blood will fill the pockets and occlude the vein ... thus preventing flow down the veins.Competent valves allow unidirectional flow ........ towards the heart . . or from superficial to deep veins.Incompetent valves .. Bidirectional flow .. Called reflux. … varicose veinsThe no. of valves in the veins increases as the veins become more distal ( calf every 2cm ) and are more common in the superficial system.
Normal unidirectional flow .. towards the heart ... in the superficial femoral vein.Note the SFA – flow away (towards the foot)FV – flow red, towards the heart
3 types of veinsPerf .. Sup to deep
include……..SFV called femoralThe deep veins of the calf include….
The lower extremity superficial system consists of the GSV (used to be called LSV), which courses down the medial aspect of the thigh and calf from the SFJ at the groin, to the ankle, and the SSV, which courses down the posterior aspect of the calf.
Connecting the two systems are perforating veins, which allow flow from the superficial venous system to the deep.Valves within the perforating veins, however, may be incompetent, allowing bidirectional flow, which we can see here with this large perforator, with a diameter of 8mm as it crosses the fascia.With augmentation, we Have flow going from the sup. System to the deep, and with release there is flow back to the superficial system.CROSSING THE deep FASCIA
.. To look for any possible reflux ( ie the valves are no longer working) …. Which may lead to the patient’s varicose veins ..
Tranducer in transverse angled upwards
Most patients can be adequately imaged with a medium frequency transducer, such as those in the 7-4MHz range.The higher frequency 10-12MHz transducers are good for thin patients, and for examining the superficial system.Some patients may require a low frequency transducer to examine the thigh in particular.Low stool to sit on - patient standing for scan .. saves back. A water soluble crayon is useful for marking over the gel at sites of importance, and a tape measure to measure distances from reproducible landmarks is essential. Can buy from any art store.
The machine set-up is optimised for a low flow state:The colour scale and filters are reduced to detect low velocity venous flow.Wall filter removes low frequencies ie from movement of vessel wall … reduce this so can pick up lower frequencies (low velocity flow in veins)The colour gain is adjusted to ensure adequate venous fillingThe sample volume is increased to ensure adequate Doppler sampling of the veinThe Doppler sweep speed is decreased to enable easier visualisation of venous flow patternsEvery machine is different .. So set up 4 ur machine. Our machines Phillips HDI 5000 .. Wall filter low, medium, high settingsIf can not augment flow, check scale , wall filter etc….. Venous pre-sets should usually be ok.
Begin with .. The patient should be standing on the floor with the leg to be examined rotated outwards, foot flat on the ground, and weight on the other leg.Depending on which veins are being examined, the patient either stands facing the examiner, or away.To examine the calf perforators and deep veins of calf, the patient sits on the edge of the bed, with the legs relaxed over the side.
Begin the examination by obtaining a patient history with regards to previous venous surgery or DVT.Helps to have an idea where the VVs are in the legHaving done this you can dim the lights and start the scan ………Before the lights go out it is also important to examine the patients legs and note the location of visible varicose veins and skin changes.
Follow gSV into calf checking 4 reflux.Find SFJ .. Check 4 reflux .. Augment calf .. Flow should be into CFV.. Reflux if flow up into GSV. If reflux into GSV check GSV down to ankle?other source of reflux?reflux into other veinsPudendal .. Drains the scrtum (male) and the labium (female) .. genatalia
In long
Identify the SSV in the posterior calf. .. ?reflux?SPJ present ?reflux. If reflux measure diameter, med/lat insertion, distance above kc.In cases where the SSV ascends into the thigh the vein is referred to as the thigh extension of the SSV or vein of Giacomini(when it connects to the GSV in the thigh). It may have variable termination sites, and it is important to document where the vein goes, particularly if the vein is incompetent. Reflux may be up or down this vein. May have reflux at SPJ, up giacomini and into GSV or down.Perforators ... check 2 c if any contributing 2 reflux.... investigate in full with patient sitting on edge of bed
If reflux in SPJ, must check for reflux in distal PopV . . . will have prox popv reflux but all going into spj
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At the completion of the study a detailed worksheet provides important information tot eh referring clinician, so it’s important it is legible and accurate, as surgeons operate off the worksheet.
A number of limitations can make the CVI scan difficult.As with any ultrasound examination, a patient’s body habitus may prevent an optimal examination. This not only applies to imaging, but large calves can be difficult to adequately augment.Extensive oedema can make visualisation of the veins difficult.Some patients may have tender legs that cannot bare the pressure needed to provide an adequate augment, making the test difficult to interpret.
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