valsalva maneuver

1- the patient is asked to do valsalva maneuver while the common femoral vein is being imaged transversely.

2-a normal response results in complete retardation of flow within the vein and resultant venous dilatation , the diameter increasing by at least 50%.

3-absence of this normal response is seen in intra luminal venous thrombosis,or external pressure applied on the vein by a pelvic tumor .

4- it could be done also with congestive heart failure

respiratory variations of the spectral wave form

1- the external iliac artery and common femoral veins should have a phasic wave form.

2-if this is lost,and the wave form is flat,then this is suspicious of either external compression from a pelvic mass or a more proximal obstructing intra luminal thrombus.

calf vein imaging

1-this is not routinely performed at every centre.

2-essentially, each of the calf arteries is accompanied with pair of veins.

3-identify first the artery and then apply distal calf compression to visualise the paired veins.

4-spontaneous flow is generally absent below knee.

5-the posterior tibial vein can be visualised by placing the probe to the medial side of the tibia.these veins are more superficially placed than the deeper sets of peroneal veins.

6-the anterior tibial veins can be visualised along the lateral aspect of the tibia.as these veins lie superficially.deeper to it ,we can visualise peroneal veins.

7-peroneal veins could be seen posteriorly through the lower leg.

8-you can visualise the calf veins while the patient is in supine position,or the patient sit up and the legs is suspended over the edge of the table with the foot on a rest.this has the effect to improve visualisation.

9-diagnostic criteria for calf veins is the same as that of the veins above knee.

10-at present,the limitation of this technique as that it will only show global thrombosis either confined to one set of veins, or through out multiple calf veins.it will not reliably and routinely detect small focal segments of thrombosis.therefore,equivocal scans or persistent symptoms may require clarifying venogram.although this could be imperfect in detection of small focal calf thrombi due to poor or non filling of the affected segment.

calf vein imaging

1-this is not routinely performed at every centre.

2-essentially, each of the calf arteries is accompanied with pair of veins.

3-identify first the artery and then apply distal calf compression to visualise the paired veins.

4-spontaneous flow is generally abscent below knee.

lower limb veins thrombosis

a positive diagnosis of deep venous thrombosis using colour flow imaging depend upon a number of factors,which include:

1-lack of spontaneous flow.

2-presence of intra-luminal reflective material.

3-vein dilatation.

4-poor response to augmentation maneuver.

5-non compressibility of the vein.

color flow imaging

1-use linear array probe 5 - 7.5 mhz.
2-patient supine with slight abduction of the thigh 10-15 degree.
3-gel applied from groin to adductor canal.
4-first,imaging done in transverse plane to identify femoral vein(medial) and artery(lateral).
5-spectral doppler analysis of both vessels.
artery--->triphasic wave form.
vein --->monophasic wave form.
6-examine external iliac vein using spectral wave form by one or the two following
a - normally , it is monophasic wave form with increase with expiration and decrease with inspiration.
-absence of this variation means----->proximal thrombosis or
----->proximal compression of the vein.
b-by valsalva maneuver.
7-by this point,imaging will be done by longitudinal scan.
8-examination of--->common femoral vein.
--->superficial femoral vein.
--->profunda femoris vein.
we can increase doppler flow by--->compression technique
and by--->by power doppler imaging.
8-turn patient in lateral decubitus with knee flexed by 20-25 degrees.
9-popliteal vein is seen anterior to popliteal artery.
10-examine popliteal vein up to adductor canal and inferiorly to tibio-peroneal trunk.
11-diagnostic criteria
*sponteneous flow:
present in patent vessel
not present in thrombotic vessel.
*intraluminal reflective material:
not present in patent vessel.
present in thrombotic vessel.
*response to distal augmentation:
present in patent vessel.
not present in thrombotic vessel.
*response to probe compression:
present in patent vessel.
not present in thrombotic vessel.
*venous dilatation:
not present in patent vessel.
present in thrombotic vessel.
*spectral wave form:
present,phasic in patent vessel.
not present in thrombotic vessel.

iliac assessment:
spectral variation is seen in patent vessel.
not seen in thrombotic vessel.
response to valsalva maneuver is seen in healthy vein
not present in thrombotic vessel.

real time compression ultrasound

1- put the probe perpendicular to the vascular flow.
2-start at groin.
3-identify common femoral vein(medial) and artery(lateral).
4-use linear array probe 5-7.5 mhz.
5-make a light pressure so the vein will not be closed.
6-then put further pressure on the vein
if it is collapsed completely(both walls opposed to each other)---> it is a healthy vein
if it is not collapsed at all or collapsed partially---> vein contains thrombus.
7-reflective thrombus could be seen within the lumen of the vein.
8-apply this technique from the groin to the adductor canal with 1 cm intervals.
9-to examine the popliteal vein turn the patient into lateral decubitus position with knee flexed.
10-then from posterior fossa , the vein will be anterior to the artery.
11-popliteal vein is followed upward to adductor canal and inferiorly to tibio-peroneal trunk.
12-at this point , examination was ended.

Lower Extremity DVT
DVT is a common clinical problem with significant associated mortality from pulmonary embolism. There are approximately 2 million cases per year and nearly 60,000 related deaths per year. DVT can be a difficult disease to diagnose because the signs and symptoms are non-specific and unreliable. Some of the signs and symptoms include calf tenderness, unilateral limb swelling, tachycardia, and tachypnea.


Diagram of the venous drainage of the lower extremity: A-Plantar venous arch; B-Posterior tibial veins; C-Peroneal veins; D-Anterior tibial veins; E-Popliteal vein; F-Femoral vein; G-Deep femoral vein; H-Common femoral vein.

Exam
1-Have the patient âs upper body elevated 10¡-20¡ and examine the leg in external rotation. Do both legs in high risk patients. In low risk symptomatic patients, do the symptomatic leg only. If the Doppler flow is continuous or dampened, sample the contralateral CFV for comparison.
2-In the transverse plane, compress each centimeter of the CFV, SFV and popliteal vein down to the trifurcation. Also identify and compress the central portions of the deep femoral and greater saphenous where these vessels join the CFV. In cases where portions of the deep venous system are poorly visualized in grey scale, longitudinal color images with color filling the vessel can be used to exclude acute DVT. Obtain representative Doppler tracings from the CFV, SFV and popliteal veins. Spontaneous and phasic flow is normal. If the flow is not phasic, assess response to augmentation. If acute thrombus is identified, determine the extent with gentle compression.
3-Calf veins should be examined in patients with anatomic calf pain and a negative femoral-popliteal exam. Follow paired posterior tibilal vein from the medial malleolus proximal. Assess peroneal veins if possible. Greater and lesser saphenous, perforators, calf muscle veins and varicosities may be evaluated if symptomatic. The region of the leg that is tender should be imaged.

Sonographic Findings of DVT:

1) Lack of complete compressibility of vein (beware: a normal femoral vein in adductor canal region may not compress).

2) Visualization of intraluminal thrombus with complete or partial obstruction of the vein lumen.

3) Distention of the vein compared to the adjacent artery

Figure A. Acute thrombus (red arrows) in lower extremity vein is hypoechoic and is commonly indistinguishable from flowing blood. The vein is distended at the site of the acute thrombus (red arrows). Figure B. Inability to compress the vein at the junction of the thrombusis (red arrows) is prime evidence of thrombus.

4) Abnormal venous Doppler signals, i.e. continuous nonphasic flow, reduced or absent flow with distal augmentation, or no obtainable signal.

A

B

A. Longitudinal color Doppler demonstrating normal blood flow in a peripheral vein. B. Longitudinal color Doppler image with transducer compression applied shows flow in the femoral artery (red arrow) and very minimal flow in the femoral vein (red arrowhead). The femoral vein does not compress with transducer pressure, indicating intraluminal thrombus.

5) Continuous, nonphasic flow in CFV unilaterally, with phasic flow in contralateral CFV, suggesting iliac vein outflow obstruction, i.e. DVT of extrinsic compression.



A

B

A. Duplex Doppler demonstrating phasic flow in a normal peripheral vein. B. Duplex Doppler demonstrating non-phasic flow in a peripheral vein with thrombosis



http://www.med-ed.virginia.edu/courses/rad/edus/index18.html

Normal phasic changes in venous flow during respiration:

During respiration there are phasic changes seen in the venous flow of the lower limb veins. This is best studied using Triplex imaging, and especially by spectral pattern of venous flow. Upper left image shows changes in flow (in superficial femoral vein), with increase during inspiration, caused by lower intra-thoracic pressure and vise versa during expiration. The Doppler image on right side shows similar changes in the popliteal vein of the same limb. This suggest continuity of flow with transmission of pressure all the way upto the vena cava and the right atrium.

http://www.ultrasound-images.com/vascular.htm

Normal compressibility of the lower limb veins:

The above 2 Doppler images show the normal superficial femoral vein (Left) and the Normal popliteal vein (Right). Compression of the veins by the Doppler probe causes the normal veins to collapse COMPLETELY (compressibility). Presence of thrombus would cause poor or absent compression of the vessels. Note that the arterial flow is not hampered by the probe pressure. However, the veins disappear in the right half of each image.

http://www.ultrasound-images.com/vascular.htm

Flow augmentation:

On applying pressure to the lower limb, distal to the veins being assessed, there is increase in flow (spectral Doppler trace). Both the superficial femoral vein (image on Left) and popliteal vein (Right) show marked increase ( flow augmentation) on applying pressure below. This suggests absence of thrombosis in the intervening parts of both veins.

http://www.ultrasound-images.com/vascular.htm

Cessation of flow on Valsalva maneuver:

Another technique to assess the patency and absence of thrombus in the part of the venous system above the point of examination is to use the Valsalva maneuver. During deep inspiration and holding of breath, there is normal abrupt cessation of flow in the vein. In image above, the superficial femoral vein shows total cessation of flow. This is therefore, normal.


http://www.ultrasound-images.com/vascular.htm

Absence of flow Lt. femoral vein (transverse section)

(longitudinal section) Lt. femoral vein

http://sites.google.com/site/drjoea/vascular

Absent flow left politeal vein


http://sites.google.com/site/drjoea/vascular

Thrombosed Lt. iliac vein


http://sites.google.com/site/drjoea/vascular

non-compressible Lt. femoral vein

http://sites.google.com/site/drjoea/vascular

Normal spectral waveforms from lower limb veins. (a) Common femoral vein waveform obtained during breath holding in an 11-year-old boy shows a, S, v, and D waves. (b) Waveform from the popliteal vein in an 11-year-old boy shows a reduced flow velocity during inspiration and an increased velocity during expiration. (c) Posterior tibial vein waveform from an 11-year-old boy shows phasic variations from respiration with mild superimposed undulation from right atrial pressure changes.

The phasic pattern of flow in lower limb veins reflects a combination of both cardiac and respiratory movements (3). Normally, all four waves that represent right atrial changes can be seen in the spectral line (Fig 10). If the S, v, and D waves are completely above the baseline and the a wave is either completely above the baseline or descends less than 5 cm/sec below it, normal antegrade flow is considered to be present. A deeper descent of the a wave below the baseline is indicative of retrograde or pulsatile flow, a pattern suggestive of increased right atrial pressure (12).

During inspiration, increased intraabdominal pressure results in a reduction of venous return from the lower limbs, which in turn leads to a decrease in the velocity or amplitude of the waveform. During expiration, flow velocities in the lower limb veins increase (3). The maximum flow velocity in femoral veins in adults is 12–30 cm/sec (13).

http://radiographics.rsna.org/content/28/3/691.full