Upper right arm swelling

Possible Causes of Swelling in the Upper Right Arm:

• Venous Thrombosis: This includes upper-extremity deep venous thrombosis (DVT), central venous thrombosis, and catheter-associated thrombosis involving peripheral and central veins such as the axillary, subclavian, and brachiocephalic veins. Patients with malignancy, indwelling central venous catheters or ports, and prior catheter thrombosis are at higher risk for multifocal central venous thrombosis presenting as unilateral arm swelling, sometimes with central venous stenosis or obstruction Magee et al. 2026 NICE CKS.
• Paget-Schroetter Syndrome (PSS) / Venous Thoracic Outlet Syndrome: This is an effort-related thrombosis of the axillary/subclavian vein seen mostly in young, active individuals involving repetitive upper limb movements causing microtrauma and anatomical thoracic outlet narrowing. It presents as unilateral arm swelling with pain, erythema, and sometimes neurological symptoms. PSS requires high clinical suspicion even if D-dimer is negative Isaac A 2025 Isaac A. 2025.
• Non-infectious Subcutaneous Emphysema: Following minor trauma, air can track into subcutaneous tissue causing swelling and crepitus, mimicking more serious infections like necrotizing fasciitis Haddad et al. 2026 Haddad et al. 2026.
• Other Causes: Cellulitis or soft tissue infection, lymphedema, traumatic injury, hematoma, and rarer causes such as malignant venous compression should also be considered (NICE CKS Cellulitis and Angio-oedema) NICE CKS,NICE CKS.

Appropriate Management:

• Evaluation: Initial assessment should include detailed history focusing on risk factors (malignancy, central catheters, repetitive limb use), thorough physical exam noting swelling, erythema, warmth, crepitus, neurovascular status, and signs of systemic infection. Blood tests including full blood count, inflammatory markers, coagulation profile, and D-dimer can assist but should not be solely relied upon to exclude thrombosis or serious pathology Isaac A 2025 Isaac A. 2025.
• Imaging: Ultrasound is first-line for suspected upper limb DVT but has limitations in detecting central venous thrombosis—especially in subclavian, brachiocephalic veins, and superior vena cava segments. If suspicion remains high despite negative peripheral ultrasound, advanced imaging with CT venography, MR venography, or catheter venography with intravascular ultrasound should be pursued Magee et al. 2026 NICE CKS. Venogram is gold standard for PSS diagnosis Isaac A 2025 Isaac A. 2025.
• Treatment of Venous Thrombosis: Anticoagulation is indicated; in complex cases such as catheter-associated or central venous thrombosis, parenteral anticoagulants and specialist input are recommended. Interventional radiology treatments such as aspiration thrombectomy and venoplasty can relieve central venous obstruction Magee et al. 2026 NICE CKS.
• Management of PSS: Early thrombolysis ideally within 10 days from symptom onset improves clot resolution. Surgical decompression by thoracic outlet decompression (TOD), involving first rib resection and muscle release, addresses the underlying anatomical cause to prevent recurrence. Lifelong or extended anticoagulation may be advised Isaac A 2025 Isaac A. 2025.
• Subcutaneous Emphysema: Differentiate benign subcutaneous emphysema from necrotizing fasciitis using clinical assessment, Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score (with score <6 suggesting low risk), and imaging. Benign cases can be managed conservatively with wound care and antibiotics avoiding unnecessary surgery Haddad et al. 2026 Haddad et al. 2026.
• Other Considerations: Treat cellulitis according to NICE guidance with appropriate antibiotics if infection suspected. Consider other differential diagnoses as indicated clinically (NICE CKS Cellulitis) NICE CKS.

Summary: Swelling in the upper right arm can arise from thrombotic, infectious, traumatic, or anatomical causes. Thorough clinical evaluation and imaging tailored to suspected pathology guide timely management. In patients with risk factors such as malignancy or central venous catheters, consider central venous thrombosis despite negative peripheral ultrasound. In young active patients, suspect Paget-Schroetter syndrome and arrange prompt imaging and surgical referral. Non-infectious subcutaneous emphysema is a rare mimic requiring careful exclusion of necrotizing fasciitis. Early recognition and appropriate intervention improve outcomes.