venous incompetence
flow dynamics
normal venous flow and valve movement,
normal flow
in the normal cicumstance, the superficial system drains the subcutaneous tissues and periodically empties into the deep system via perforating veins.
flow direction should always be:
- cephalad.
- superficial to deep.
incompetent valve & perforator leading to venous reflux.
incompetent flow
with distal augmentation, flow initially goes cephalad. it then refluxes back down the leg through the malfunctioning valve.
an incompetent perforating vein also allows blood to flow from the deep veins to the surface veins.
this combination of back pressure causes dilation and tortuosity of the veins (ie varicosites).
normal vein valve
normal venous valve.
leg vein anatomy
nomenclature
ref: journal of vascular surgery, special communication, 2005. (215kb pdf file)
we recommend reviewing this thorough document.
importantly, to avoid confusion, the ‘long saphenous’ is now the ‘great saphenous’.
what are varicose veins
below is a basic outline of the anatomy and function of the veins and what constitutes venous incompetence. be aware however that there are numerous anatomical variations.
valves
the veins contain a series of valves along their course, preventing retrograde flow back down the leg. these valves operate like two plastic doors opening up the leg. if back pressure is applied, they swing closed, pushing against each other, blocking reverse flow down the leg.
if functioning normally, it is a competent valve. if blood is able to pass backwards though the valve, it is deemed incompetent.
depending on the extent of incompetence, this backflow will dilate the supple superficial veins making them tortuous and dilated(varicose veins).
causes include:
familial factors with ‘lax’ veins. these distend slightly allowing the valve leaflets to no longer oppose each other.
injury or thrombosis. both of these can lead to adherance of valve leaflets to the vein wall, rendering the valve useless.
the deep veins
are the primary route for returning blood to the heart. they collect the venous blood from all the draining muscular and superficial veins.
in the lower limb the deep veins are: (from groin to ankle)
- common femoral vein (cfv)
- superficial femoral vein (sfv)- also called just the femoral vein.
- popliteal vein (popv)
- anterior tibial (atv)
- posterior tibial (ptv
- peroneal veins (per v)
the latter 3 are calf veins that generally run in pairs (venous commantantes)
the superficial veins
there are 2 main superficial veins draining the subcutaneous tissue of the lower leg:
the great saphenous vein (gsv) runs from the medial malleolus, up the medial aspect of the leg, draining into the cfv at the groin as the sapheno-femoral junction (sfj).
the short saphenous vein (ssv) runs up the posterior midline of the calf. it may drain into the proximal popv above the knee crease as the sapheno-popliteal junction (spj). commonly however, it may continue up the posterior thigh as the giacomini vein. this will terminate either into the mid/distal sfv or ascend to drain into the proximal lsv.
incompetence of the sfj and spj are the two primary sources of varicose veins.
sapheno-femoral junction
- the termination of the great saphenous vein (gsv) into the common femoral vein (cfv) in the groin.
- is the primary source of venous incompetence and varices of the lower limb.
sapheno-femoral junction anatomy
sapheno-femoral junction anatomy
deep veins
- common femoral vein (cfv)
- superficial femoral vein (sfv)
- proffunda femoris vein (proffv)
superficial veins:
- long (great) saphenous vein (lsv)
- medial accessory saphenous vein (masv)
- lateral accessory saphenous vein (lasv)
sapheno-popliteal junction
- the termination of the short saphenous vein (ssv) into the popliteal vein (popv) in the popliteal fossa.
- the spj is absent in 25% of the population, continuing up the posterior thigh as the giacomini vein.
- only 15% of people have a midline spj. the remaining junctions are medial/lateral, often via a gastrocnemius vein.
(both ref: “the vein book” author: john j. bergan)
sapheno-popliteal (spj) anatomy diagram.
the sapheno-popliteal junction
determine competency and the relationship to the knee crease.
the junction is commonly into the lateral aspect of the popliteal vein.
common variations are:
- via muscular veins.
- no spj – giacomini vein variant up to the sfv or lsv in the thigh.
diagram of transverse calf showing the ‘eye-like’ fascia containing the ssv.
the short saphenous vein may terminate in the giacomini vein with no sapheno-popliteal junction.
alternatively it may divide, with a normal spj and a giacomini vein (as in this case).
scan protocol
role of ultrasound
note: a comprehensive thorough scan can take an hour to complete.
- to identify the source and course of varicosities in the lower limb.
- to assess these veins pre-operatively as a cause for:
- venous ulcers
- lower limb oedema
- venous ezcema
- self image
limitations
- ideally the scan should be performed with the patient erect or as upright as possible. some patient will have difficulty with this.
- markedly oedematous legs or open ulcers will impede scan quality.
patient preparation
- ideally the scan should be performed with the patient erect or as upright as possible. some patients will have difficulty with this, occasionally becoming faint or weary.
- use of a tilt table will make the scan easier for both you and the patient.
- position the patient on their back. gently flex their knee and externally rotate their leg with their unaffected leg kept straight to take the majority of their weight.
equipment setup
- use of a medium to high frequency(7-10mhz)linear array probe is preferrable to visualise the superficial veins.
- you may need to resort to a lower frequency probe to assess the deep veins, depending on the patient’s body habitus.
- doppler settings should be low prf and low wall filter with medium to high persistance.
- set the u/s machine to display triplex – usually, when spectral doppler is on, there is a ‘simultaneous’ option
common pathology
scanning technique
deep veins
post thromotic syndrome in patients with a past history of dvt can lead to deep venous incompetence. deep venous incompetence or current dvt is important to exclude as a cause for the patients symptoms.
- begining at the groin in transverse, identify the common femoral vein(cfv) at the point where it bifurcates into the superficial femoral vein(sfv) and proffunda femoris vein(pfv).check compresibility in transverse and image in longitudinally with colour flow.
- the external iliac vein (and often cfv) do not have valves so need not be checked for incompetence.
- check the competency of the sfv proximally:in longitudinal, using colour and spectral doppler. ask the patient to strain down and make a fat tummy. if incompetent, flow reversal will be evident throughout the strain. note: due to valve spacing you can get up to 0.5 seconds of reversed flow in deep veins.
- check the patency and competency of the sfv distally: if the sfv was incompetent proximally, valsalva can be used again, otherwise a short, firm squeeze of the proximal calf (called augmentation) should be used.
- check the patency and competency of the popliteal vein(popv). place the probe transversely in the popliteal fossa at the knee crease. the popv and artery will be easily seen (be cautious not to mistake the several muscular veins in the area for the popv). check it’s competency as per the distal sfv.
the great saphenous vein (gsv)
sometimes referred to as the long saphenous vein (lsv).
- follow from the sapheno-femoral junction (sfj) groin to the ankle using distal augmentation to assess for incompetence.
- if there are changes in competence, note the distance from landmarks such as the groin or knee crease.
the short saphenous vein
- similar to the gsv, in longitudinal, follow the ssv from the sapheno-popliteal junction (spj) in the knee crease, down the midline of the calf.
- use distal augmentation to assess for incompetence.
- if there are changes in competence, note the distance from landmarks such as the malleoli or knee crease.
- the sural nerve runs parallel to the ssv from mid calf down to the heel. if the ssv is incompetent, make note in the report if the sural nerve is in intimate contact with the vein. they can be confused one for the other in surgery.
perforating veins
a perforating vein joins the superficial veins to the deep veins. by definition a perforating vein must breech the fascia between the superficial fat and the muscle fascia.
in transverse, scan in a methodical patternup and down the medial calf. begin with the toe of the probe on the tibia and do vertical sweeps until you reach the ssv.
flow should always be superficial to deep (competent).
if flow is observed deep to superficial, the vein is incompetent. any incompetent perforating veins (ipvs) or competent perforators >3mm should be noted in the report.
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common perforators the most common perforating veins are shown. the ‘cocketts’ are by far the most common. these are medial, paratibial in the distal 2/3 of the lower leg. |
basic hardcopy imaging
a cvi study should include the following minimum images:
- cfv bifurcation
- sfv proximal and distal demonstrating patency and competency
- popv demonstrating patency and competency
- sfj demonstrating patency and competency
- spj (if present) demonstrating patency and competency
- any incompetent perforators noting their diameter, depth and position relative to a surface landmark
- any significant or atypical junctions of varices to the ‘normal’ system
- any incidental pathology such as thrombus, bakers cyst or popliteal aneurysm.