What is the differential diagnosis for a patient presenting with left arm swelling and pain for 1 week without a history of trauma or fever?

Differential Diagnosis for Left Arm Swelling and Pain Without Trauma or Fever

Immediate Life-Threatening Consideration

Upper extremity deep vein thrombosis (UEDVT) is the most critical diagnosis to exclude urgently, as it accounts for up to 10% of all DVTs and can lead to pulmonary embolism. 1, 2 Unilateral arm swelling indicates an obstructive process at the level of the brachiocephalic, subclavian, or axillary veins and requires urgent evaluation. 1, 2

Primary Differential Diagnoses

1. Upper Extremity Deep Vein Thrombosis (UEDVT)

• Clinical presentation: Ipsilateral upper-extremity edema (80% of cases), pain (75%), prominent superficial veins serving as collaterals around the obstruction, and heaviness distal to the thrombus 3, 1
• Key risk factors to assess:
  • Indwelling venous devices (catheters, pacemakers, defibrillators) - highest risk 1
  • Active malignancy creating hypercoagulable state 1
  • Recent surgery or trauma 1
  • History of dialysis access (AV fistula or graft) 1
• Distinguishing features: Bulging veins represent collateral circulation bypassing the obstructed deep venous system—a hallmark of venous thrombosis 1

2. Central Venous Stenosis/Obstruction

• Clinical presentation: Ipsilateral extremity swelling without other cause, particularly in patients with dialysis access 1
• Key feature: Swelling persisting beyond 2 weeks after dialysis access placement requires investigation 1
• Mechanism: Venous hypertension from downstream stenosis forces blood flow through venous collaterals, producing chronic venostasis 1

3. Soft Tissue Infection

• Clinical presentation: Swelling with effacement of fat planes, possible gas formation, or foreign bodies 3, 2
• Note: Absence of fever does NOT exclude infection—radiographic findings may show soft tissue swelling, joint effusion, or ulcers 3
• Differential includes: Cellulitis, myositis, tenosynovitis, or abscess formation 3

4. Venous Insufficiency/Thrombosis Complications

• Clinical presentation: Persistent hand edema following side-to-side anastomosis for arteriovenous fistula, invariably from downstream stenosis 1
• Associated findings: Hematoma formation with obvious discoloration and swelling, particularly in early stages of fistula use 1

5. Musculoskeletal Pathology

• Considerations: Tumors (benign or malignant), arthritides, metabolic conditions 3
• Key point: Radiographs help exclude fractures and tumors as causes of swelling or pain 3

Immediate Diagnostic Algorithm

Step 1: Urgent Duplex Ultrasound

• Perform immediately to exclude UEDVT—sensitivity and specificity above 80% 1, 2
• Grayscale imaging: Directly visualizes echogenic thrombus and assesses vein compressibility; lack of compression indicates acute or chronic thrombus 1
• Doppler assessment: Evaluates blood flow patterns, cardiac pulsatility, and respiratory variation; dampening indicates central venous obstruction 1
• Sniffing maneuver: Test for central vein collapse with rapid inspiration; impaired collapse suggests central obstructive process 1

Step 2: Plain Radiographs (Two Planes)

• Mandatory first investigation for any suspected musculoskeletal pathology with swelling 2
• Purpose: Excludes fractures, tumors, and provides anatomic overview 3
• Findings to assess: Soft tissue swelling, gas, foreign bodies, erosions, periosteal reaction, or bone sclerosis 3

Step 3: If UEDVT Confirmed

• Initiate therapeutic anticoagulation immediately following standard DVT treatment protocols 1, 2
• Investigate lower extremities if no local cause identified, as correlation between upper and lower extremity DVT exists 1

Step 4: If Ultrasound Negative but High Clinical Suspicion

• Proceed to CT venography (CTV) or MR venography (MRV) if central venous stenosis suspected and ultrasound cannot visualize thoracic vessels adequately 1
• CTV with IV contrast: Demonstrates venous thrombosis and collateral circulation in neutral and elevated arm positions 1

Step 5: If Infection Suspected

• Obtain image-guided aspiration for culture—imaging cannot distinguish infected from noninfected fluid collections 3, 2
• Advanced imaging: MRI or CT with IV contrast to assess soft tissue extent and guide aspiration or surgical debridement 3, 2

Step 6: If Tumor Suspected

• MRI of entire compartment with adjacent joints when malignancy cannot be excluded on radiographs 2
• Critical: Refer to bone sarcoma center before biopsy; all biopsies must be performed by surgeon who will perform definitive resection 2

Critical Pitfalls to Avoid

• Do NOT dismiss unilateral swelling as benign—it indicates obstruction requiring urgent evaluation, unlike bilateral swelling which suggests systemic causes 1, 2
• Do NOT wait for fever to develop before considering infection—radiographic findings may be present without systemic signs 3
• Recognize catheter-associated UEDVT may be asymptomatic initially, manifesting only as catheter dysfunction before progressing to overt swelling 1
• Do NOT attribute unilateral swelling with bulging veins to neurogenic thoracic outlet syndrome—this presentation demands urgent evaluation for venous obstruction 1

Follow-Up Protocol

• Reassess within 48-72 hours to evaluate response to initial management and ensure no progression 1, 2
• Schedule formal evaluation at 6 weeks if edema persists to detect delayed complications or underlying pathology maturation 1, 2