Abnormal intimal-medial thickness measurements on B-mode imaging.

http://emedicine.medscape.com/article/1155193-overview

Abnormal intimal-medial thickness measurements on power Doppler imaging.

http://emedicine.medscape.com/article/1155193-overview

Normal intimal-medial thickness measurements on B-mode imaging.

http://emedicine.medscape.com/article/1155193-overview

Normal intimal-medial thickness measurements on power Doppler imaging.

http://emedicine.medscape.com/article/1155193-overview

High-grade stenosis as seen on spectral analysis. Note the high frequencies and velocities (532 cm/s systolic and 281 cm/s diastolic).

http://emedicine.medscape.com/article/1155193-overview

Power Doppler: Observation of flow is independent of velocity or direction.

http://emedicine.medscape.com/article/1155193-overview

Internal carotid artery as seen on spectral analysis. Note that flow is continuous through diastole.

http://emedicine.medscape.com/article/1155193-overview

External carotid artery as seen on spectral analysis. Note the absence of flow in diastole and the sharp upstroke in systole.

http://emedicine.medscape.com/article/1155193-overview

Typical carotid bifurcation seen on grayscale.

http://emedicine.medscape.com/article/1155193-overview

Definition

Deep venous thrombosis is a condition in which a blood clot forms in a vein that is deep inside the body.

Causes

Deep venous thrombosis (DVT) mainly affects the large veins in the lower leg and thigh. The clot can block blood flow. If the clot breaks off and moves through the bloodstream, it can get stuck in the brain, lungs, heart, or other area, leading to severe damage.

Risks for DVT include:

• Immobility which causes blood flow in the veins to be slow. Slow flowing blood is more likely to clot than normal flowing blood.
  • A surgical operation which lasts more than 30 minutes is the most common cause of a DVT. The legs become still when you are under anaesthetic. Blood flow in the leg veins can become very slow.
  • Any illness or injury that causes immobility increases the risk of a DVT.
  • Long journeys by plane, train, etc are thought to cause a slightly increased risk of DVT. This is probably due to sitting cramped for long periods.
• Faulty blood clotting is an uncommon cause. One example is an inherited condition that causes the blood to clot more easily than normal (factor V leiden).
• The contraceptive pill and hormone replacement therapy (HRT) which contain oestrogen can cause the blood to clot slightly more easily. Women taking ‘the pill’ or ‘HRT’ have a small increased risk of DVT.
• Damage to the inside lining of the vein increases the risk of a blood clot forming. For example, a DVT may damage the lining of the vein. So, if you have already had a DVT, then you have a higher than average risk of having another one sometime in the future.
• Older people are more likely to have a DVT, particularly if you have poor mobility or have a serious illness such as cancer.
• Pregnancy increases the risk. About 1 in 1000 pregnant women have a DVT.
• Obesity also increases the risk of having a DVT.
• Bedrest
• Cigarette smoking
• Fractures
• Giving birth within the last 6 months

You’re also more likely to develop DVT if you have any of the following conditions:

• Blood that is more likely to clot (hypercoagulability)
• Cancer
• Overproduction of red blood cells in bone marrow (polycythemia vera) or related conditions

DVTs are most common in adults over age 60, but can occur at any age.

Symptoms

• Changes in skin color (redness) in one leg
• Increased warmth in one leg
• Leg pain in one leg
• Leg tenderness in one leg
• Swelling (edema) of one leg

This picture shows a red and swollen thigh and leg caused by a blood clot (thrombus) in the deep veins in the groin (iliofemoral veins) which prevents normal return of blood from the leg to the heart.

Exams and Tests

Your health care provider will perform a physical exam. The exam may show a red, swollen, or tender leg.

The following tests may be done:

• Doppler ultrasound exam of a limb

Discussion:
- allows assessment of DVT from the external iliac vein down to the poplieal veins;
- visualization distal to the popliteal viens is usually not possible;
- may be able to detect patency of major vessels, but it is not effective for smaller vessels;
- will not diagnose pelvic thrombi;
- note that clots seen on ultrasound comprise a spectrum from clots in the calf (usually not seen), to clots on the femoral valve cusps (non occlusive), to occlusive deep venous thrombosis which extends from the popliteal vessels to the proximal vessels (the latter is associated with higher risk of PE);
- note that the reliability of the ultrasound study is very user dependent (more experienced technicians will give a more accurate study);

How to do DVT U/S?

Patient positioning when assessing the femoral vein.

Patient positioning when assessing the popliteal vein.

Probe positioning for assessment of the femoral vein.

Ultrasonographic image of femoral vessels without compression.

Ultrasonographic image of femoral vessels with compression. ( If veins are not fully compressible —> DVT )

Probe positioning for assessment of the popliteal vein.

Ultrasonographic image of popliteal vessels with clot.

Normal anatomy of lower limb veins.

BASIC IMAGING

An ankle series should include the following minimum images;

• CFV: pre/post compression
• Proffunda femoris
• SFV proximal TS: pre/post compression
• SFV proximal LS: with colour doppler
• SFV distalTS: pre/post compression
• SFV distal LS: with colour doppler
• POPV TS: pre/post compression
• POPV LS: with colour doppler
• Posterior tibial veins LS colour doppler
• Peroneal veins LS colour doppler
• Sapheno-femoral-junction
• Document the normal anatomy. Any pathology found in 2 planes, including measurements and any vascularity.

diagnostic criteria for DVT:
- visualization of an intraluminal thrombus in a deep vein
- lack of compressibility of the venous lumen;
- filling of the lumen w/ echoes;
- diminished Doppler waveforms;
- lack of augmentation of venous flow w/ compression of calf muscles;
- lack of effect of respiration on the Doppler wave form;

LIMITATIONS

Obese patients, or those with severe oedema will limit the scan quality resulting in only being able to exclude occlusive thrombus Acoustic windows and detail may be limited in patients with open wounds/sutures.

Treatment

For years, the standard treatment has been a medication called heparin, which stops blood clots from forming. This type of medicine is called an anticoagulant (also known as a blood thinner).

If heparin is given continuously through a vein (IV), you must stay in the hospital. However, newer forms of heparin that can be given by injection once or twice a day can sometimes be used. You may not need to stay in the hospital as long, or at all, if you are prescribed this newer form of heparin.

The drug warfarin is usually prescribed along with heparin. Warfarin is taken by mouth and is usually used for long-term therapy. It takes several days to fully work. Heparin is continued until the warfarin has been fully effective for at least 24 hours. People usually take warfarin for a minimum of 3 months, but sometimes they must take it for the rest of their lives, depending on their risk for another clot.

You will need frequent lab tests to check the thickness of your blood when you first start taking warfarin. This lets your health care provider properly adjust your dose.

In rare cases, surgery may be needed if medicines do not work. Surgery may involve:

• Placement of a filter in the body’s largest vein to prevent blood clots from traveling to the lungs
• Removal of a large blood clot from the vein or injection of clot-busting medicines

Possible Complications

A blood clot that breaks free in the leg and travels to the lungs (pulmonary embolus) can be life threatening. Rapid treatment of DVT helps prevent this problem.

When to Contact a Medical Professional

Call your health care provider if you have symptoms of DVT.

Go to the emergency room or call the local emergency number (such as 911) if you have DVT and you develop chest pain, difficulty breathing, coughing blood, fainting, loss of consciousness, or other severe symptoms.

Prevention

Doctors may prescribe blood thinners to help prevent DVT in people at high risk, or those who are undergoing high-risk surgery.

Sometimes patients in the hospital wear special soft boots that automatically (and gently) squeeze the calves periodically. This is called intermittent pneumatic compression. It helps keep blood moving and prevents blood clotting.

Moving your legs often during long plane trips, car trips, and other situations in which you are sitting or lying down for long periods of time can also help prevent DVT.

In summary

• The main cause of DVT is immobility – especially during surgery.
• The most serious complication of DVT is a pulmonary embolus where part of the blood clot breaks off and travels to the lung.
• Persistent calf symptoms may occur after a DVT.
• With treatment, the risk of the above two complications is much reduced.
• Treatment includes anticoagulation, compression stockings, leg elevation, and keeping active.
• Prevention is important if you have an increased risk of DVT. For example, during long operations or when you travel on long journeys.

References :

1. http://www.wheelessonline.com/ortho/site_index
2. http://www.e-radiography.net/radpath/d/dvt.htm
3. http://www.nlm.nih.gov/medlineplus/ency/imagepages/2549.htm
4. http://www.vascularweb.org/patients/NorthPoint/Deep_Vein_Thrombosis.html

pearls for diagnosis

1-• Be sure the veins fully compress.
2-Be sure to apply pressure evenly along the transducer face (perpendicular to skin surface). 3-Avoid pressing at an angle, as this may result in uneven compression and a false positive finding. 3-In patients who are obese, decreasing the transducer frequency to 3.5-5 MHz increases the depth of penetration and can assist the examiner. Overall image quality, however, is reduced.
4- If no vein is visible at the appropriate anatomic sight, the transducer may already be compressing the vein. Reduce the amount of pressure being applied and reexamine the area of interest.
5-Care must be taken to not over-interpret vessel echogenicity as clot. Both normal blood flow and vessel artifact can appear hyperechoic. Cysts, especially Baker cysts, are commonly encountered in the popliteal region.
6-These can be readily distinguished by their confluence with the joint space and their lack of flow on color flow Doppler ultrasonography.
7-Lymph nodes are particularly common in the femoral region and can be identified by their superficial location, their characteristic appearance (hyperechoic center with hypoechoic rim), and their high vascularity on color flow Doppler ultrasonography
8- Duplicate popliteal and femoral veins are not uncommon. Special attention must be paid to rule out a DVT in patients with a duplicate vessel because the potential decrease in flow velocity may increase the risk for clot development.
9- Utilizing the dual-image picture or split-screen option before and after compression may make comparison easier. In addition, the split-screen option may be useful in hospitals that use still images for documentation. If the examination site is wounded, the ultrasound transducer may be covered with a sterile probe cover with gel applied to both the inside and the outside of the cover.If an adequate examination cannot be obtained secondary to patient body habitus, patient compliance, or skill limitation, the patient requires a formal ultrasonographic study. In addition, if the study results are indeterminate, then a formal ultrasonographic study should be obtained.


http://www.google.com.eg/imgres?imgurl=http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-104340-1362989-1383583.jpg&imgrefurl=http://emedicine.medscape.com/article/1362989-treatment&usg=__ZZqorDtsU0B_SDuAwNfox0jcGUE=&h=306&w=311&sz=40&hl=ar&start=7&zoom=1&itbs=1&tbnid=OvfkZRH5cvC8mM:&tbnh=115&tbnw=117&prev=/images%3Fq%3Dposterior%2Btibial%2Bvein%2Bthrombosis%26hl%3Dar%26sa%3DG%26gbv%3D2%26tbs%3Disch:1

Posterior tibial vein
-This longitudinal view reveals that more than half of the venous lumen is occluded by thrombus (black area). Areas of blood flow within the vein appear red. This imaging technique renders a thrombus as black, while areas of blood flow are colorised.


http://www.thrombosisadviser.com/scripts/pages/en/resources/image-library/index.php

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.

Deep vein thrombosis: scintigraphic diagnosis with In-111-labeled monoclonal antifibrin antibodies.

1-Fifty-two patients suspected of having deep vein thrombosis under-went scintigraphy with an indium-111-labeled monoclonal antifibrin antibody.
2- Venography disclosed deep vein thrombosis in 31 patients.
3-With the whole limb considered an anatomic entity, antifibrin antibody scintigrams obtained 2 hours after injection had a specificity and sensitivity of 81% and 84%, respectively.
4-A higher sensitivity (92%) was found for a subgroup of patients (n = 44) with symptoms for less than 10 days.
5-Regional sensitivities for all patients and for the subgroup, respectively, were 92% and 100% in the calf, 82% and 94% in the popliteal region, 63% and 71% in the thigh, and only 18% and 13% in the pelvis. Additional imaging performed 6 hours and 21 hours after injection in 12 patients and quantitative analysis done from scintigrams with and without blood-pool (technetium-99m human serum albumin) correction did not improve sensitivity. In-111-antifibrin antibody scintigraphy is an accurate method for diagnosis of acute established deep vein thrombosis of the calf and popliteal region; its sensitivity in the thigh is lower, and it is not feasible for diagnosis in the pelvic area.


http://www.ncbi.nlm.nih.gov/pubmed/2678259