Edema - Differential Diagnosis

Edema is the accumulation of excessive fluid in the subcutaneous tissue. When edema results from lymphatic stasis, the term lymphoedema is used.

Causes: 

Generalized Edema :

1. Increased plasma hydrostatic pressure: 

• Congestive heart failure
• Vasodilatory drugs: e.g nifedipine

2. Decreased plasma oncotic pressure: 

• Liver disease
• Renal disease e.g Nephrotic syndrome
• Malnutrition
• Malabsorption

3. Increased capillary permeability:

• Angioedema 
• Anaphylaxis.

Localized Edema:

1. Impairment of Lymphatic drainage:

• Milroy's disease
• Lymphoedema praecox
• Malignant infiltration
• Infection- Elephantiasis
• Radiation
• Surgical damage

2. Local infection

3. Trauma:

• Mechanical trauma
• Burns
• Animal bites/stings

Clinical History: 

1. Site and Distribution: Enquires should be made regarding the site of edema, as localized and demarcated sites are usually due to trauma or infection. Edema may be cinfined to both lower limbs for example with Inferior vena cava obstruction or pregnancy, or may affect a single limb in DVT.

2. Past Medical And Drug History : is important as edema can result from interruption to lymphatic drainage following an irradiation surgery or metastatic tumors. .Certain drugs may cause edema as side effect so detailed history for drug intake in necessary.

3. Associated Symptoms: may point towards a certain organ system as the cause of edema

• Cardiac failure: Lethargy, dyspnoea, orthopnea, cough, ankle edema
• Liver disease: Jaundice, pruritis,abdominal distension, hematemesis, confusion
• Renal disease: Severe generalized edema, frothy urine
• Malabsorption: weight loss, diarrhea, steatorrhoea
• Venous thrombosis: Unilateral leg swelling (DVT)

Physical Examination: 

1. Assess the distribution of edema which may help in narrowing the differential diagnosis. 

• Generalized causes tend to present with dependent pedal edema.

2. In cardiac failure there will be tachycardia and an elevated JVP. Bilateral coarse pulmonary crepitations can be auscultated. Hepatomegaly due to liver congestion may also be present.

3. Examine the abdomen and look for organomegaly and ascites.

4. Generalized wasting may be seen in malabsorption and malnutrition. 

5.  Clubbing, palmar erythema, DUpuytren's contracture, jaundice, spider naevi, gynecomastia are signs of liver disease.