What are the causes of lower leg edema?

Causes of Lower Leg Edema

Lower leg edema can be caused by a wide range of conditions affecting cardiovascular, renal, hepatic, endocrine, and local vascular systems, with the most common causes being cardiac failure, venous insufficiency, medication side effects, and renal disorders. 1

Primary Categories of Lower Leg Edema

Cardiac Causes

• Right heart failure: Causes increased central venous hypertension leading to increased capillary permeability and plasma volume 1
• Biventricular failure: Similar mechanism as right heart failure 1
• Heart failure with preserved ejection fraction: Results in fluid retention and increased hydrostatic pressure 1

Hepatic Causes

• Liver cirrhosis/failure: Decreases protein synthesis leading to decreased plasma oncotic pressure, increased systemic venous hypertension, and increased capillary permeability 1

Renal Causes

• Kidney disease/nephrotic syndrome: Increases protein loss leading to decreased plasma oncotic pressure and increased plasma volume through sodium/water retention 1

Endocrine Disorders

• Thyroid and adrenal disorders: Cause abnormal water excretion and hyponatremia 1

Vascular Causes

• Venous insufficiency: Most common cause of bilateral edema in older patients 2
• Deep vein thrombosis: Usually presents as unilateral swelling 3
• Lymphedema: Can be primary or secondary, presents with brawny, non-pitting edema 4
• Nonthrombotic iliac vein lesions (NIVL): Typically leads to asymmetrical swelling 1

Other Systemic Causes

• Obstructive sleep apnea: Increases pulmonary vascular resistance, pulmonary hypertension, and resultant capillary hydrostatic pressure 1
• Allergic causes: Angioedema and urticaria increase capillary permeability 1
• Malabsorption and malnutrition: Decrease protein synthesis and plasma oncotic pressure 1
• Pregnancy-related: Increases plasma volume 1
• Premenstrual edema: Increases plasma volume 1
• Idiopathic edema: Unknown mechanism, often seen in females 5

Medication-Induced Edema

• Calcium channel blockers: Common cause of bilateral edema 1
• Vasodilators: Cause fluid retention 1
• NSAIDs: Promote sodium retention 1
• Other medications: Various mechanisms 2

Local/Anatomical Causes

• Peripheral arterial disease (PAD): Can present with edema, especially in advanced cases 1, 6
• Popliteal arterial entrapment syndrome (PAES): Most common cause of surgically correctable lower-extremity vascular insufficiency in young adults 1
• External iliac artery endofibrosis (EIAE): Rare cause seen primarily in endurance athletes 1
• Buerger disease: Nonatherosclerotic inflammatory vasculitis affecting small and medium-sized distal arteries 1

Diagnostic Approach Based on Presentation

Unilateral Edema

• More likely due to:
  • Deep vein thrombosis
  • Local infection or inflammation
  • Lymphatic obstruction
  • Pelvic mass compressing venous return
  • Post-thrombotic syndrome
  • Nonthrombotic iliac vein lesions 1

Bilateral Edema

• More likely due to:
  • Cardiac failure
  • Renal disease
  • Hepatic disease
  • Medication side effects (especially calcium channel blockers)
  • Lymphedema
  • Bilateral superficial venous reflux
  • Systemic conditions 1

Key Clinical Considerations

• The distribution of edema (unilateral vs. bilateral) provides important diagnostic clues 3
• Timing of onset (acute vs. chronic) helps narrow the differential diagnosis 3
• Associated symptoms such as dyspnea, pain, skin changes, or pigmentation guide diagnosis 3
• Pitting vs. non-pitting edema helps distinguish between different etiologies (non-pitting suggests lymphedema) 4
• Extent of edema (ankle only vs. extending to thigh) may indicate severity and underlying cause 1

Common Pitfalls in Diagnosis

• Assuming all bilateral edema is cardiac in origin
• Missing medication-induced causes
• Overlooking coexisting peripheral neuropathy in diabetic patients 6
• Premature use of diuretics without identifying underlying cause 2
• Failing to consider multiple contributing factors, especially in older patients 2

Understanding the diverse causes of lower leg edema is essential for appropriate management and preventing complications such as skin breakdown, venous ulcers, and decreased quality of life.