Deep vein thrombosis: Clinical sciences

Deep vein thrombosis, or DVT, is a blood clot that develops in the deep veins, most commonly of the lower limbs. Less commonly, DVT can form in the deep veins of the arms or mesenteric veins of the bowel.

The pathogenesis of DVT centers around the Virchow triad, which includes venous stasis, hypercoagulability, and endothelial injury.

If untreated, the thrombus can lead to limb ischemia, hemodynamic instability, pulmonary embolism, and even death.

Now, if your patient presents with signs and symptoms suggestive of DVT, first you should perform an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and start continuous vital sign monitoring, including pulse oximetry, blood pressure, and heart rate. If needed, provide supplemental oxygen to maintain the oxygen saturation above 92%.

Alright, now let’s go back to the ABCDE assessment and discuss how to manage stable individuals. First, obtain a focused history and physical examination. History usually reveals pain, swelling, and warmth in the affected limb as well as DVT risk factors,

such as age above 65, recent surgery, prolonged immobilization, and active cancer, as well as smoking and obesity.

Also keep in mind that estrogen increases the risk of venous thrombosis, so pregnancy and the use of oral contraceptives are also important risk factors.

Finally, a family history of DVT can indicate a familial inheritance of genetic conditions predisposing to DVT, such as Factor V Leiden mutation.

On the other hand, the physical examination usually reveals edema, erythema, warmth, and tenderness of the affected area.

In some individuals, you might even be able to palpate the thrombotic vein.

Another important test is to see if you can elicit the Homan sign.

To do this, lift the affected leg and slightly bend it in the knee. Next, abruptly and firmly perform dorsiflexion of the patient’s foot.

The Homan sign is positive if dorsiflexion of the foot results in deep calf pain. But, here’s the thing! Even though it’s associated with DVT, the Homan sign is not sufficiently specific or sensitive to confirm the diagnosis because it’s often positive in individuals without DVT.

At this point you can suspect DVT. So, at this point your next step is to order labs, including CBC, D-dimer, and coagulation profile, as well as renal and liver studies.

Now, while you are waiting for lab results, use a validated metric, such as the Wells criteria, to predict the likelihood of DVT.

The Wells criteria scores historical findings, physical findings, and alternative diagnoses.

Historical findings are worth 1 point and include: a history of prior DVT; active cancer; surgery or prolonged bed rest within 3 months; or any recent condition that has weakened or immobilized the suspect limb, like a splint.

Physical features are also worth 1 point and they include: localized pitting edema of the affected leg; swelling of the entire lower limb; calf circumference asymmetry of 3 cm or greater in the affected leg; tenderness over a deep leg vein; or collateral vein distention in the affected leg.

Finally, if you are considering alternative diagnoses, like cellulitis or a ruptured Baker cyst, then you’ll subtract 2 points from the score.