View source for Ultrasonography of deep vein thrombosis of the lower extremity

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|author1=[[User:Mikael Häggström|Mikael Häggström]]
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==Planning==
===Indication===
''Wells score or criteria'' help categorize patients into low risk versus high risk:

#Active cancer (treatment within last 6 months or palliative): +1 point
#Calf swelling ≥ 3&nbsp;cm compared to asymptomatic calf (measured 10&nbsp;cm below tibial tuberosity): +1 point
#Swollen unilateral superficial veins (non-varicose, in symptomatic leg): +1 point
#Unilateral pitting edema (in symptomatic leg): +1 point
#Previous documented DVT: +1 point
#Swelling of entire leg: +1 point
#Localized tenderness along the deep venous system: +1 point
#Paralysis, paresis, or recent cast immobilization of lower extremities: +1 point
#Recently bedridden ≥ 3&nbsp;days, or major surgery requiring regional or general anesthetic in the past 12 weeks: +1 point
#Alternative diagnosis at least as likely: −2 points<ref name="Hargett"/>

:'''Less than 1: Low risk'''<ref name="Diagnosis"/><ref name="Hargett"/>
:'''Greater than 2: High risk'''<ref name="Diagnosis">{{cite journal |vauthors=Bates SM, Jaeschke R, Stevens SM | title=Diagnosis of DVT: Antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines | journal=Chest | year= 2012 | volume= 141 | issue= suppl 2 | pages= e351S–e418S | pmid=22315267 | doi=10.1378/chest.11-2299 |pmc=3278048|display-authors=etal}}</ref><ref name="Hargett">{{cite journal |vauthors=Hargett CW, Tapson VF| title=Clinical probability and D-dimer testing: How should we use them in clinical practice? | journal=Semin Respir Crit Care Med | year= 2008 | volume= 29 | issue= 1 | pages= 15–24 | pmid=18302083 | doi=10.1055/s-2008-1047559}}</ref>

[[File:Swedish algorithm of deep vein thrombosis.png|thumb|center|Swedish algorithm.<ref>{{cite web|title=Djup ventrombos, DVT|website=Internetmedicin|author=Docent Henry Eriksson, Med dr, överläkare Fariba Baghaei, Specialistläkare Valerie Bockisch, Professor emerita Margareta Hellgren, Docent Leif Lapidus, Överläkare Per-Åke Moström, Med dr, Överläkare Vladimir Radulovic, Överläkare Lennart Stigendal|url=https://www.internetmedicin.se/page.aspx?id=1206}} Updated 2017-06-11</ref>]]

The threshold for normal versus high D-dimer is generally 500 ng/mL or 0.5 mg/L.<ref>{{cite journal  |vauthors=Ageno W, Finazzi S, Steidl L, etal |title=Plasma measurement of D-dimer levels for the early diagnosis of ischemic stroke subtypes |journal=Archives of Internal Medicine |volume=162 |issue=22 |pages=2589–93 |year=2002 |pmid=12456231 |url=http://archinte.jamanetwork.com/article.aspx?volume=162&page=2589 |doi=10.1001/archinte.162.22.2589}}</ref> In pregnant or elderly patients, corresponding D-dimer ranges need to be used.<ref group="notes">
;Pregnant patients
Upper limit of reference range for D-dimer:
{|class="wikitable"
! Units !! Nonpregnant <br>adult !! First trimester !! Second trimester !! Third trimester
|-
| mg/L or µg/mL	|| < 0.5 || < 0.95 || < 1.29 || < 1.7
|-
| µg/L or ng/mL	|| < 500 || < 950 || < 1290 || < 1700
|-
| nmol/L || < 2.7 || < 5.2 || < 7.1 || < 9.3
|}
<font size=1>Reference: [http://www.perinatology.com/Reference/Reference%20Ranges/D-Dimer.htm Reference Values During Pregnancy] at perinatology.com. Retrieved October 2014.</font>

;Elderly patients:
Patient’s age in years × 10 µg/L (or x 0.056 nmol/L) for patients aged over 50 years for the suspicion of venous thromboembolism (VTE).
<br><font size=1>References: 
*{{cite journal |vauthors=Urban K, Kirley K, Stevermer JJ |title=PURLs: It's time to use an age-based approach to D-dimer |journal=J Fam Pract |volume=63 |issue=3 |pages=155–8 |date=March 2014 |pmid=24701602 |pmc=4042909 |doi= |url=}}
*{{cite journal |last1=Raja |first1=Ali S. |last2=Greenberg |first2=Jeffrey O. |last3=Qaseem |first3=Amir |last4=Denberg |first4=Thomas D. |last5=Fitterman |first5=Nick |last6=Schuur |first6=Jeremiah D. |title=Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians |journal=Annals of Internal Medicine |date=29 September 2015 |volume=163 |issue=9 |pages=701 |doi=10.7326/M14-1772 |pmid=26414967}}</font></ref>

In certain circumstances, it may also be indicated in suspected pulmonary embolism, see '''[[pulmonary embolism]]'''.

==Evaluation==
[[File:Ultrasonography of deep vein thrombosis of the femoral vein -annotated.jpg|thumb|[[Doppler ultrasonography]] showing absence of flow and hyperechogenic content in thrombosed femoral vein.]]
Start as high as possible in the inguinal region where you can clearly see the external iliac vein, and then follow the femoral vein and popliteal vein with the probe. Compress the vein at regular distances, such as totaling at least 7 locations. Look for:
*Hyperechoic content.
*Absence of compressibility. However, adequate compression is usually not possible by the area where the vein passes through the adductor hiatus.
A decrease in Doppler flow raises the suspicion, but has less sensitivity and specificity.

===Lower leg===
If a lower ultrasound of the lower leg is indicated in the algorithm above, also evaluate the posterior tibial veins (at least distally near the ankle), the fibular veins (either beneath the posterior tibial vein, better seen when going about half way up the lower leg) as well as the anterior tibial vein (at least proximally).
<gallery widths=250 heights=180>
File:Ultrasonography of thrombosis of the fibular veins, coronal plane, annotated.jpg|Coronal plane, seen from medial side of lower leg, showing thrombosis of the fibular veins, with hyperechoic content and only marginal blood flow.
</gallery>
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