Home > Browse Emergency Issues
<< Deep Venous Thrombosis: Identifying The Killer Before It Strikes
Differential Diagnosis
It is critical to distinguish between DVT and its various mimics. Regrettably, several of these alternative diagnoses can actually coexist in the presence of DVT, making the correct diagnosis all the more critical. A long list of potential etiologies can lead to bilateral lower extremity swelling, including DVT, peripheral arterial disease, CHF, venous stasis, trauma, and cellulitis. However, Sheiman et al evaluated 500 patients (mostly inpatients) referred for duplex imaging, and of these, 50 were found to have bilateral lower extremity swelling. None of these 50 patients had DVT identified, and most had histories suggesting other reasons for leg swelling.39
Cellulitis
The difficulty distinguishing cellulitis from DVT stems from the tendency of a cellulitis patient’s leg or arm to appear swollen from the edema secondary to localized infection. This edema and swelling in turn causes discomfort when an examiner squeezes the leg or arm. Laboratory tests may not be specific enough to help differentiate the 2 disease entities adequately; in fact, there are no diagnostic lab tests for DVT. Furthermore, the white blood cell count may not be elevated in cellulitis and may be elevated with a DVT. It is of considerable help when the area of erythema is far removed from the path of any deep veins in the leg, such as the anterior lower leg. However, when this is not the case, there can be doubt distinguishing between DVT and cellulitis clinically. Hence, there is often little choice but to seek an imaging study for guidance toward a diagnosis.
Baker’s Cyst
An occasional finding on lower extremity duplex ultrasound is the presence of a Baker’s cyst. This cyst is a herniation of the synovial membrane of the knee joint through the posterior aspect of the joint capsule. Upon rupture, the pain from dissecting fluid can be intense, and these patients often present with calf pain and swelling. An ultrasound examination allows visualization of either the actual cyst or the fluid left behind after a cyst has ruptured. Once the cyst is located, the sonologist will still need to confirm the patency of the popliteal vein to exclude proximal DVT.
Superficial Thrombophlebitis
Thrombosis of a superficial vein, such as the great saphenous, can be quite uncomfortable for a patient. The course of the great saphenous vein is close enough to deep veins in several regions of the leg to make symptom locations overlap. It is important to remember that, while treatment in most cases may only require simple measures, like heat and aspirin, full anticoagulation may occasionally be indicated. In cases where the thrombus is seen in the proximal great saphenous vein and is at the point of inflow into the femoral vein, or for those patients with significant, known hypercoagulability, treatment is similar to proximal DVT. Use of duplex ultrasound is sometimes necessary to confirm the thrombosis of a superficial versus a deep vein. As previously noted, it may behoove the EP to confirm the location of the superficial thrombosis in high-risk patients, especially considering that nearly 25% of all patients with superficial phlebitis were found to have involvement of the deep system in one study.43 Older patients — particularly males over 60 — patients with systemic infections, and those subjected to bed rest run a higher risk for progression of superficial phlebitis to DVT.44 Intravenous drug users can also develop septic thrombophlebitis from skin penetration under nonsterile conditions.
Trousseau’s syndrome, also known as Nygaard- Brown syndrome, refers to the association sometimes seen between visceral cancer and DVT in both the lower and upper extremity. Classically, the association is seen with pancreatic tumors, but other cancers, such as adenocarcinomas, can cause it.45
Musculoskeletal Pain
Popliteus tendonitis, bursitis of the knee, rupture of the soleus, Achilles tendon rupture, osteoarthritis, bone fracture, and muscle strain can all mimic DVT pain. The Thompson squeeze test involves compression of the calf muscle half way down the lower leg in a patient who is lying prone, with the knee flexed and ankle relaxed. A positive test, when the foot fails to passively plantarflex, indicates a complete rupture of the Achilles tendon. However, it is important to note that, in many cases, enough fibers of a tendon will remain intact, despite severe injury, to give a false-negative test. When in doubt, ultrasound is a rapid and highly accurate diagnostic tool and can even be performed at the bedside. It is not uncommon for patients to present several days after trauma to the lower extremity. Patients with a history of “trauma” to a lower extremity and pain in a suggestive location should raise one’s suspicion for DVT. For patients who are on anticoagulants, as well as the occasional serious athlete, a hemorrhage into the calf musculature can present with calf pain and swelling of significant severity. Although history is usually helpful, ultimately many of these limbs will still require imaging.
Any venous stasis can lead to lower extremity swelling and sometimes pain. This is especially likely for patients who have previously had a DVT and who present with an acute postthrombotic syndrome or a worsening of chronic symptoms. Differentiating either of these from acute DVT is difficult based on a physical examination alone, and typically ancillary testing is required.
Cellulitis
The difficulty distinguishing cellulitis from DVT stems from the tendency of a cellulitis patient’s leg or arm to appear swollen from the edema secondary to localized infection. This edema and swelling in turn causes discomfort when an examiner squeezes the leg or arm. Laboratory tests may not be specific enough to help differentiate the 2 disease entities adequately; in fact, there are no diagnostic lab tests for DVT. Furthermore, the white blood cell count may not be elevated in cellulitis and may be elevated with a DVT. It is of considerable help when the area of erythema is far removed from the path of any deep veins in the leg, such as the anterior lower leg. However, when this is not the case, there can be doubt distinguishing between DVT and cellulitis clinically. Hence, there is often little choice but to seek an imaging study for guidance toward a diagnosis.
Baker’s Cyst
An occasional finding on lower extremity duplex ultrasound is the presence of a Baker’s cyst. This cyst is a herniation of the synovial membrane of the knee joint through the posterior aspect of the joint capsule. Upon rupture, the pain from dissecting fluid can be intense, and these patients often present with calf pain and swelling. An ultrasound examination allows visualization of either the actual cyst or the fluid left behind after a cyst has ruptured. Once the cyst is located, the sonologist will still need to confirm the patency of the popliteal vein to exclude proximal DVT.
Superficial Thrombophlebitis
Thrombosis of a superficial vein, such as the great saphenous, can be quite uncomfortable for a patient. The course of the great saphenous vein is close enough to deep veins in several regions of the leg to make symptom locations overlap. It is important to remember that, while treatment in most cases may only require simple measures, like heat and aspirin, full anticoagulation may occasionally be indicated. In cases where the thrombus is seen in the proximal great saphenous vein and is at the point of inflow into the femoral vein, or for those patients with significant, known hypercoagulability, treatment is similar to proximal DVT. Use of duplex ultrasound is sometimes necessary to confirm the thrombosis of a superficial versus a deep vein. As previously noted, it may behoove the EP to confirm the location of the superficial thrombosis in high-risk patients, especially considering that nearly 25% of all patients with superficial phlebitis were found to have involvement of the deep system in one study.43 Older patients — particularly males over 60 — patients with systemic infections, and those subjected to bed rest run a higher risk for progression of superficial phlebitis to DVT.44 Intravenous drug users can also develop septic thrombophlebitis from skin penetration under nonsterile conditions.
Trousseau’s syndrome, also known as Nygaard- Brown syndrome, refers to the association sometimes seen between visceral cancer and DVT in both the lower and upper extremity. Classically, the association is seen with pancreatic tumors, but other cancers, such as adenocarcinomas, can cause it.45
Musculoskeletal Pain
Popliteus tendonitis, bursitis of the knee, rupture of the soleus, Achilles tendon rupture, osteoarthritis, bone fracture, and muscle strain can all mimic DVT pain. The Thompson squeeze test involves compression of the calf muscle half way down the lower leg in a patient who is lying prone, with the knee flexed and ankle relaxed. A positive test, when the foot fails to passively plantarflex, indicates a complete rupture of the Achilles tendon. However, it is important to note that, in many cases, enough fibers of a tendon will remain intact, despite severe injury, to give a false-negative test. When in doubt, ultrasound is a rapid and highly accurate diagnostic tool and can even be performed at the bedside. It is not uncommon for patients to present several days after trauma to the lower extremity. Patients with a history of “trauma” to a lower extremity and pain in a suggestive location should raise one’s suspicion for DVT. For patients who are on anticoagulants, as well as the occasional serious athlete, a hemorrhage into the calf musculature can present with calf pain and swelling of significant severity. Although history is usually helpful, ultimately many of these limbs will still require imaging.
Any venous stasis can lead to lower extremity swelling and sometimes pain. This is especially likely for patients who have previously had a DVT and who present with an acute postthrombotic syndrome or a worsening of chronic symptoms. Differentiating either of these from acute DVT is difficult based on a physical examination alone, and typically ancillary testing is required.
Sign up for free access