EDEMA

Edema is a clinical term to denote excess accumulation of fluids in interstitial fluid compartment, which normally contributes to ~15% of TBW.

Etiology: Edema is caused by any factor that: (a) reduces plasma oncotic pressure, (b) increases hydrostatic pressure, (c) increases capillary permeability, and (d) prevents lymphatic return (Table 7.2).

Diagnostic approach: Although the edema per se is a clinical diagnosis, etiological diagnosis requires detailed history, clinical examination and relevant investigations. Important differentiating features of edema include:

• Onset: Allergic or toxic edema due to increased capillary permeability develops rapidly within a

TABLE 7.2: Causes of edema

a. Reduced oncotic pressure (hypoproteinemia)

- Nutritional kwashiorkor (4 intake)

- Malabsoprtion syndrome (4 absorption)

- Chronic liver disease (4 synthesis)

- Nephrotic syndrome (#8593; renal loss)

- Protein-losing enteropathies ( GIT loss)

- Burns (#8593; skin loss)

- Pleural effusion/peritonitis ( third space loss)

b. Increased hydrostatic pressure

- Cardiac: CCF, pericarditis, hypertension

- Extra-cardiac: Budd-Chiari syndrome, mediastinal mass

- Water retention: Renal failure, steroids, fluid overload

c. Increased capillary permeability

- Allergic: Urticaria, angioneurotic edema

- Toxic: Septicemia, epidemic dropsy

- Inhammatory: Infections, burns

d. Lymphatic obstruction

- Congenital anomalies: Lymphangioma

- Acquired: Filariasis, traumatic, surgical few hours, while other causes lead to gradual and progressive edema.

• Distribution: Generalized edema is usually nutritional, renal or cardiac in origin. Renal edema typically begins from face as periorbital puffiness, while cardiac or nutritional edema is most prominent over dependent parts, e.g. legs in older children and sacrum in infants.

Localized edema is seen in: (a) lymphatic obstruction, (b) allergic conditions, e.g. angioneurotic edema, (c) localized vascular compressions, and (d) early stages of generalized edema.

• Diurnal variation: Renal edema is maximum in morning due to overnight fluid retention, while cardiac edema is more prominent in evening due to gradual decompensation after physical activity.

• Pitting vs. non-pitting edema: While severe edema is grossly visible, presence of mild/moderate edema may be confirmed by compressing on a bony part,

e. g. shin of the tibia for gt;10 sec. Pitting subcutaneous edema indicates interstitial fluid accumulation.

Non-pitting edema is rare in children, seen in: (a) hypothyroidism or myxedema, (b) obesity, and (c) long-standing edema with secondary changes, e.g. lymphatic filariasis.

• Co-existing features of primary disease also help in differential diagnosis, e.g. itching (allergic causes), jaundice (hepatic disease), anuria/oliguria (renal disease), cardiac signs, etc.

7.1.3