Diagnostic Studies of Deep venous
thrombosis.
nClinical
examination alone is able to confirm only 20-30% of cases of DVT
nBlood
Tests
nthe
D-dimer
n
INR.
nCurrent
D-dimer assays have predictive value for DVT, and the
n
INR is useful for guiding the management of patients with known DVT who
are on warfarin (Coumadin)
D-dimer
nD-dimer
is a specific degradation product of cross-linked fibrin. Because
concurrent production and breakdown of clot characterize thrombosis,
patients with thromboembolic disease have elevated levels of D-dimer
nthree
major approaches for measuring D-dimer
nELISA
nlatex
agglutination
nblood
agglutination test (SimpliRED
nFalse-positive
D-dimers occur in patients with
n
recent (within 10 days) surgery or trauma,
n
recent myocardial infarction or stroke,
n
acute infection,
n
disseminated intravascular coagulation,
n
pregnancy or recent delivery,
nactive
collagen vascular disease, or metastatic cancer
Imaging Studies
nInvasive
Ø
venography,
Øradiolabeled
fibrinogen and.
n
noninvasive
Øultrasound,
Øplethysmography,
ØMRI
techniques
venography
ngold
standard” modality for the diagnosis of DVT
nAdvantages
nVenography
is also useful if the patient has a high clinical probability of
thrombosis and a negative ultrasound,
n
it is also valuable in symptomatic patients with a history of prior
thrombosis in whom the ultrasound is non-diagnostic.
side effects
nphlebitis
nanaphylaxis
Nuclear Medicine Studies
nBecause
the radioactive isotope incorporates into a growing thrombus, this test
can distinguish new clot from an old clot
Plethysmography
nPlethysmography
measures change in lower extremity volume in response to certain stimuli.
Ultrasonography
ncolor-flow
Duplex scanning is the imaging test of choice for patients with suspected
DVT
ninexpensive,
n
noninvasive,
nwidely
available
nUltrasound
can also distinguish other causes of leg swelling, such as tumor,
popliteal cyst, abscess, aneurysm, or hematoma.
clinical limitations
nexpensive
nreader
dependent
nDuplex
scans are less likely to detect non-occluding thrombi.
nDuring
the second half of pregnancy, ultrasound becomes less specific, because
the gravid uterus compresses the inferior vena cava, thereby changing
Doppler flow in the lower extremities
Magnetic Resonance Imaging
nIt
detects leg, pelvis, and pulmonary thrombi and is 97% sensitive and 95%
specific for DVT.
n
It distinguishes a mature from an immature clot.
n
MRI is safe in all stages of pregnancy.
Differential
diagnosis
|