DEEP VEIN THROMBOSIS

Definition

Deep vein thrombosis is a condition by which blood changes from liquid to solid state and produces a blood clot (thrombus) within the deep venous system typically in the lower limbs

Grayscale Ultrasound

Acute thrombosis (- 14 days)

• Low echogenicity• Venous distension: Recently larger than accompanying artery• Loss of compressibility:• Free floating thrombus:• Collateralization: Tortuous and braided collateralveins, usually smaller than the normal vein

Subacute thrombosis (- 2 weeks to 6 months)

• more echogenic, variable• Decrease thrombus and vein sizel• Adherence of thrombus: Free floating thrombusbecomes attached to vein wall• Resumption of flow: Luminal flow may berestored; but vein may remain occluded• Collateralization: Collateral continues to develop

Chronic phase

(~ 6 months)• Post-thrombotic scarring:

Thrombus becoming organized as fibrous tissue

• Wall thickening: with reduced luminal diameter

• Echogenic intraluminalmaterial: may occasionally calcify

• Synechiae: Formed from un lysed thrombus that is attached to one side of the vein wall and gradually transformed into a fibrous band

• Fibrous cord: In veins which fail to recanalize,

• Valve abnormalities: thickening of valve cusps and restricted cusp motion may result leading to reflux and venous stasis

Pulsed Dopplero Spontaneous flow (any waveform present)• Expected in medium to large veins, but flow is often not spontaneous in smaller calf veins

o Phasic flow (variation in flow velocity with respiration)

• When phasic pattern is absent, flow is described as continuous, indicating the presence of obstruction closer to the heart

o Valsalva maneuver• Causes abrupt cessation of blood flow in large and medium size veins documenting patency of venous system from point of examination to thorax

o Augmentation (increase in flow velocity with distal compression)

• Absence of this response indicates presence of obstruction further away from the heart to the site of examination

Color Doppler

- Useful to detect low echo or anechoic thrombus which may be missed on grayscale US

- Demonstration of recanalized lumen in the thrombus and collateralization

- Demonstration of reflux in valvular incompetence

• Power Doppler: Particularly useful in the

demonstration of slow flow through recanalized

lumen and collaterals

Imaging Recommendations

• Best imaging toolo Duplex Doppler ultrasound is first line imaging investigation with sensitivity and specificity for acute symptomatic DVT between 90-100%

o CECT and MR/MR venography are good non-invasive imaging tools for assessment of pelvic veins and IVC and for exclusion of pelvic and abdominal causes of DVT

o Conventional venography has a false negative rate of 11% and should be reserved for use as problem solving aid

DIFFERENTIAL DIAGNOSIS

Interpretation Errors

• Baker cyst, artifactual "echocontrast" from slow flow,

thickened valve mistaken for thrombus in chronic

venous obstruction, failure to identify duplicated vein

Technical Errors

• Inadequate compression, improper use of color flow

image, poor venous distension, misidentification of

deep vs. superficial veins

CLINICAL ISSUES• Most common signs/symptoms

o Acute DVT: Swollen and tender lower limb (extent of swelling depends on site of DVT), increased temperature

o Post thrombotic syndrome: Sequelae of DVT resulting from chronic venous obstruction and/or acquired incompetence of valves

o Chronic leg swelling, ankle pigmentation, and ulceration in the lower calf and ankle (gaiter zone)

• Other signs/symptoms: Signs and symptoms from pulmonary embolism: Shortness of breath, pleuriticchest pain, tachycardia, hypoxia, hypotension

Image Interpretation Pearls

• Thrombus is excluded if the vein is completely compressed

Transverse ultrasound shows acute DVT of the popliteal vein,

filled with hypoechoicthrombus (right) and

incompressible with transducer pressure

(left).

Corresponding longitudinal color doppler ultrasound

shows vein with absent intraluminal color signal while the artery posterior to it demonstrates complete color filling.

Transverse ultrasound

shows thrombosis of the common femoral vein (CFV)

The vessel is non-compressible (right side of image).

Corresponding longitudinal

color Doppler ultrasound

shows DVT of CFV with

partial color filling.

Longitudinal color

Doppler ultrasound shows acute thrombosis of the

superficial femoral vein

(SFV)

Longitudinal color Doppler

ultrasound shows acute

thrombosis of the popliteal vein

Longitudinal color

Doppler ultrasound shows thrombosis of one of the posterior tibial veins (PTV)

Longitudinal

color Doppler ultrasound

shows a normal posterior

tibial artery accompanied

by a pair of normal,patent,

posterior tibial veins .

Note that calf veins are

usually paired.

Longitudinal color

Doppler ultrasound shows acute thrombosis of the

peroneal veins. Note

paired thrombosedperoneal veins are accompanied by small peroneal artery .

Transverse

ultrasound shows chronic DVT of the SFV.

The thrombosed vein is

contracted and filled with echogenicthrombus.

Longitudinal

ultrasound shows a soleal vein thrombosis with intraluminalincompressible, hypoechoic thrombus.

Note sluggish flow in the

soleal vein may mimic

venous thrombosis.

Longitudinal color Doppler ultrasound shows chronic DVT with partial recanalization of thrombus

Transverse ultrasound

shows chronic DVT with a contracted thrombus.

Longitudinal ultrasound shows chronic DVT within the CFV.

Note the thrombosedvein contains multiple calcifications with acoustic shadowing.

Longitudinal pulsed

Doppler ultrasound shows

the normal variation in

Phasic flow in the SFV Note

phasic variation is absent

and becomes continuous if

an obstructing lesion is

present between the site of

examination and heart.

Longitudinal pulsed

Doppler ultrasound shows

normal augmentation in the

SFV when the calf is

compressed. This indicates

there are no obstructing

lesions between the site of

examination and calf

MR venogram of the

common femoral veins

external iliac veins common iliac veins and

inferior vena cava.

Contrast was injected

simultaneously via pedal

veins in both feet.

MRV shows obstruction to flow of contrast at the origin of the left external iliac vein (f/V) =indicating

thrombosis of the left f/V

Oblique CECT shows

Non enhancing thrombus

within the infra renallVC.

Distance between the left

renal vein BI and the top of

the IVC thrombus was

measured (26.3 mm) for

assessment of suitability for

IVC filter deployment.

IVC cavogram with pigtail catheter positioned above the common iliac vein confluence. An IVC filter is seen within the

Infrarenal lVC with thrombus (filling defects) trapped within it.