Deep vein thrombosis is a blood clot that forms within the deep veins, usually in the legs. Ultrasound is the primary imaging tool used to diagnose DVT and distinguish between acute, subacute, and chronic clots based on characteristics like echogenicity, size, and adherence to vein walls. Doppler ultrasound can further evaluate venous blood flow and identify areas of obstruction. While ultrasound is very accurate, other modalities like CT, MRV, and conventional venography may be used in specific cases to identify clots in other veins or rule out other causes.

1. DEEP VEIN THROMBOSIS

2. 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

3. 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
collateral
veins, 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
thrombus
becomes attached to
vein wall
• Resumption of flow:
Luminal flow may be
restored; but vein may
remain occluded
• Collateralization:
Collateral continues to
develop
Chronicphase
(~ 6 months)
• Post-thrombotic scarring:
Thrombus becoming organized
as fibrous tissue
• Wall thickening: with
reduced luminal diameter
• Echogenic intraluminal
material: 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

4. Pulsed Doppler
o 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

5. 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

6. Imaging Recommendations
• Best imaging tool
o 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

7. 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

8. 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, pleuritic
chest pain, tachycardia, hypoxia, hypotension

9. Image Interpretation Pearls
• Thrombus is excluded if the vein is
completely compressed

10. Transverse ultrasound
shows acute DVT of
the popliteal vein,
filled with hypoechoic
thrombus (right) and
incompressible with
transducer pressure
(left).

11. Corresponding
longitudinal color
doppler ultrasound
shows vein with absent
intraluminal color
signal while the
artery posterior to it
demonstrates
complete color filling.

12. Transverse ultrasound
shows thrombosis of
the common femoral
vein (CFV)
The vessel is non-compressible
(right
side of image).

13. Corresponding
longitudinal
color Doppler
ultrasound
shows DVT of CFV with
partial color filling.

14. Longitudinal color
Doppler ultrasound
shows acute
thrombosis of the
superficial femoral vein
(SFV)

15. Longitudinal color
Doppler
ultrasound shows acute
thrombosis of the
popliteal vein

16. Longitudinal color
Doppler ultrasound
shows thrombosis of
one of the posterior
tibial veins (PTV)

17. 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.

18. Longitudinal color
Doppler ultrasound
shows acute
thrombosis of the
peroneal veins. Note
paired thrombosed
peroneal veins are
accompanied by small
peroneal artery .

19. Transverse
ultrasound shows
chronic DVT of the
SFV.
The thrombosed vein is
contracted and filled
with echogenic
thrombus.

20. Longitudinal
ultrasound shows a
soleal vein thrombosis
with intraluminal
incompressible,
hypoechoic thrombus.
Note sluggish flow in the
soleal vein may mimic
venous thrombosis.

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

22. Transverse ultrasound
shows chronic DVT with
a contracted
thrombus.

23. Longitudinal ultrasound
shows chronic DVT
within the CFV.
Note the thrombosed
vein contains
multiple calcifications
with acoustic
shadowing.

24. 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.

25. 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

26. 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.

27. 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

28. 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.

29. 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.