Venous thromboembolism: Clinical

Our bodies are constantly maintaining a fine balance between making and breaking blood clots. In the late 1800s, doctor Rudolf Virchow identified three factors that contribute towards the formation of clots: hypercoagulability, stasis of the blood, and endothelial injury. If there’s any factor that tips the balance towards forming clots then a venous thromboembolism, or VTE can develop. VTE can cause two clinical presentations: deep vein thrombosis, or DVT, and pulmonary embolism, or PE. They are clumped together because they share the same pathophysiology, and often a DVT leads to a PE.

Risk factors for VTE revolve around Virchow’s triad, and can be remembered with the mnemonic “THROMBOSIS”: “T” is for trauma or history of travel. “H” is for hospitalization and hormones, meaning any form of exogenous estrogen such as hormone replacement therapy, tamoxifen or combined oral contraceptives, which promote the formation of clots in the venous circulation. “R” is for relatives, that is family history of inherited hypercoagulable disorders, like Factor V Leiden. “O” is for old age. “M” is for having any malignancy. “B” is for long bone fractures. “O” is for obesity and obstetrics; that is pregnancy and the early post-partum period. “S” is for any form of major surgery, especially orthopedic surgery as well as smoking. “I” is for immobilization, such as a paralyzed limb. And the final “S” is for other sickness, like antiphospholipid syndrome, nephrotic syndrome, and paroxysmal nocturnal hemoglobinuria.

Alright, now DVTs usually involve the deep veins of the lower extremity, such as the proximal iliac and femoral veins, or the distal popliteal veins. Upper extremity DVTs are very rare, and if they do happen, it’s usually because of an indwelling intravascular catheter. Now, individuals with DVT usually develop a swollen, red and painful unilateral limb. That sounds nonspecific, so it’s important to differentiate DVT from superficial thrombophlebitis, cellulitis, lymphedema, and Baker cysts. On physical exam, a great telltale sign of DVT is a large calf diameter relative to the unaffected leg. A commonly taught finding is the Homan’s sign; which is calf pain on passive dorsiflexion of the foot, but this finding is unreliable. The rare but severe presentations of DVT have latin names - phlegmasia cerulea dolens, which translates to a painful blue swelling, and phlegmasia alba dolens, which translates to painful white swelling. Painful blue swelling can occur due to massive iliofemoral thrombosis, which causes severe venous congestion in the affected limb. Painful white swelling can occur due to a massive thrombosis that gets so big that it compresses nearby arteries, causing the leg to become pale due to arterial insufficiency and ischemia.