Dvt from harrissons

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Deep Vein Thrombosis (DVT)

Harrison's Principles of Internal Medicine, 22nd Edition (2025) - Chapter 290

Classification

Lower extremity DVT usually begins in the calf and can propagate proximally to the popliteal, femoral, and iliac veins. Leg DVT is approximately 10 times more common than upper extremity DVT.

Upper extremity DVT is often precipitated by placement of pacemakers, internal cardiac defibrillators, or indwelling central venous catheters. The likelihood increases with catheter diameter and number of lumens.

Superficial venous thrombosis presents with erythema, tenderness, and a "palpable cord." Superficial veins may be visible in the chest wall (Urschel's sign). Patients are at risk for extension into the deep venous system.

Clinical Evaluation

The most common symptom is a cramp or "charley horse" in the lower calf that persists and intensifies over several days.

Clinical Pearls (DVT mimics to know)

Ruptured Baker's cyst - sudden, severe calf discomfort
Cellulitis - fever and chills
Diffuse leg edema - DVT is unlikely in a diffusely edematous leg, except in phlegmasia cerulea dolens (the most serious form)
May-Thurner syndrome - recurrent left thigh edema in young women, due to right proximal iliac artery compressing the left proximal iliac vein
Massive DVT - marked thigh swelling, tenderness, erythema
Upper extremity DVT - asymmetry in the supraclavicular fossa or upper arm circumference

Wells Score for DVT (Table 290-2)

Clinical Variable	Points
Active cancer	+1
Paralysis, paresis, or recent cast	+1
Bedridden >3 days; major surgery <12 weeks	+1
Tenderness along distribution of deep veins	+1
Entire leg swelling	+1
Unilateral calf swelling >3 cm	+1
Pitting edema	+1
Collateral superficial nonvaricose veins	+1
Alternative diagnosis at least as likely as DVT	-2

Low likelihood: score 0 or less
Moderate likelihood: score 1-2
High likelihood: score 3 or greater

Patients with low likelihood should undergo D-dimer testing first. If normal, no imaging is needed. Patients with high clinical likelihood should skip D-dimer and proceed directly to imaging.

Differential Diagnosis of DVT

Condition
Ruptured Baker's cyst
Muscle strain/injury
Cellulitis
Acute postthrombotic syndrome/venous insufficiency

Diagnostic Tests

D-Dimer

Sensitivity >95% for PE; also elevated in DVT
A normal D-dimer rules out DVT/PE in patients with low pretest probability
Not specific - elevated in MI, pneumonia, sepsis, cancer, postoperative state, 2nd/3rd trimester pregnancy
Age-adjusted D-dimer (for patients >50 years): upper limit = age × 10 ng/mL (e.g., 700 ng/mL for a 70-year-old)
Note: Age-adjusted D-dimer does NOT apply to suspected acute DVT (only PE)
D-dimer has limited utility in hospitalized patients due to frequent elevations from systemic illness

Imaging

Compression Ultrasound - the principal diagnostic test for DVT. A non-compressible vein is diagnostic of DVT. Visualization of intraluminal clot is not required. DVTs commonly form at venous junctions (high turbulence), so compression is performed at major branch points.
MR Venography with gadolinium - used when pelvic or leg ultrasound is equivocal. Excellent for diagnosing DVT.
Contrast phlebography - now largely replaced by venous ultrasonography; reserved for when an interventional procedure is planned.

DVT in Special Contexts

Cancer-Associated DVT (Trousseau's Syndrome)

DVT and PE are the most common thrombotic conditions in cancer patients
Trousseau's syndrome: coexistence of migratory/recurrent thrombophlebitis with visceral carcinoma (especially pancreatic cancer)
~15% of patients with new DVT/PE have an underlying cancer diagnosis
Postoperative DVT is twice as common in cancer patients
~11% annual risk of VTE in patients receiving chemotherapy (6-fold higher than general population)
Chemotherapy agents associated with increased risk: bleomycin, L-asparaginase, nitrogen mustard, thalidomide analogues, cisplatin-based regimens, high-dose busulfan and carmustine
D-dimer is less predictive of DVT in cancer patients

DVT in Pregnancy

Aggressive diagnosis and management of suspected DVT optimizes outcomes
Anticoagulation with LMWH or unfractionated heparin is indicated (DOACs and warfarin are avoided)
Prophylactic LMWH: stop 12 hours before epidural catheter placement
Therapeutic LMWH: stop 24 hours before epidural placement
Transition to unfractionated heparin near delivery shortens the gap before epidural placement

Perioperative VTE Prophylaxis

Aspirin alone is not supported for thromboprophylaxis
Moderate-risk patients: low-dose UFH (≤5000 units SC bid), LMWH (enoxaparin 30 mg bid or 40 mg qd), or fondaparinux 2.5 mg qd
High-risk patients: UFH 5000 units SC tid
DOACs: Rivaroxaban 10 mg once daily after nonmajor orthopedic surgery reduced VTE events vs. enoxaparin without significantly increasing bleeding
Graduated compression stockings and pneumatic compression devices are useful adjuncts or alternatives when anticoagulants carry excessive bleeding risk

Key Points Summary

DVT typically starts in the calf and propagates proximally
Use Wells score to stratify clinical probability before ordering tests
Low probability + normal D-dimer = effectively rules out DVT
High probability = go straight to imaging, skip D-dimer
Compression ultrasound is the gold standard diagnostic test
A non-compressible vein segment = DVT (no need to see thrombus directly)
Diffuse leg edema argues against DVT (except phlegmasia cerulea dolens)
Consider May-Thurner syndrome in young women with recurrent left leg DVT
Cancer dramatically increases DVT risk; consider occult malignancy in unprovoked DVT
In pregnancy, use LMWH or UFH - never DOACs or warfarin

- Harrison's Principles of Internal Medicine, 22nd Edition (2025), Chapter 290

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