Edema and-effusions

Edema and-effusions

1. Edema and Effusions Prof Rajendra Dhaka, MBBS DCP MD PhD.

2. Accumulation of fluid in tissues – edema. Accumulation of fluid in body cavities – effusion. Mostly due to disturbed cardiovascular, renal or hepatic function. Vascular hydrostatic pressure ⇄ colloid osmotic pressure of plasma = salt and water. Small net movement of fluid into interstitium drains into lymphatic vessels to return to the blood stream through thoracic duct. This helps the tissues remain dry.

3. Elevated hydrostatic pressure or diminished colloid osmotic pressure results in increased movement of fluid out of vessels. If this exceeds the rate of lymphatic drainage result is edema of tissues and effusion if adjacent body cavity is involved. Fluids may be inflammatory or non-inflammatory. Inflammatory (exudates) – due to increased vascular permeability due to inflammatory mediators. Usually localized and rich in proteins.

4. Generalized in systemic inflammation as in sepsis, which produce widespread endothelial injury. Non-inflammatory (transudates) – protein poor, are common in heart failure, liver failure, renal disease and nutritional disorders such as Marasmus and Kwashirkor .

5. Factors affecting fluid movement across capillary walls

6. Pathophysiologic categories of edema

7. INCREASED HYDROSTATIC PRESSURE – most commonly due to impaired venous return. Localized impairment is as seen in deep venous thrombosis (DVT) seen in lower extremity with resultant edema. Systemic increase in venous pressure is seen in congestive heart failure (CHF) with widespread edema.

8. REDUCED PLASMA OSMOTIC PRESSURE – albumin accounts for almost half of total plasma proteins. Inadequate synthesis/increased loss of albumin are common causes of reduced osmotic pressure. Reduced albumin synthesis occurs in severe liver disease as cirrhosis, and protein malnutrition. Loss of albumin is seen in nephrotic syndrome in which it leaks through permeable glomerular capillaries.

9. SODIUM AND WATER RETENTION – reduced volume and renal hypoperfusion cause hyperaldosteronism resulting in salt and water retention. This results in increased hydrostatic pressure due to intravascular volume expansion and diminished vascular colloid osmotic pressure due to dilution.

10. LYMPHATIC OBSTRUCTION – impaired clearance of interstitial fluid results in lymphedema of the affected part. Trauma, fibrosis, invasive tumors and infectious agents can disrupt lymphatic vessels. Filariasis due to parasite infection causes elephantiasis. Marked edema of upper extremity after surgical removal/irradiation of breast and axillary lymph nodes in patients with breast cancer.

11. Morphology Subcutaneous edema in high hydrostatic pressure. Also affected by gravity as dependent edema in recumbent position. It is also pitting on finger pressure which displaces interstitial pressure. Cardiac/renal. Renal edema – initially appears in loose connective tissue such as periorbital. Pulmonary edema – tissue becomes 2-3 times weighty due to fluid and lack of air. Brain edema – local/generalized, narrow sulci and distended gyri.

12. Effusion – pleural, peritoneal, chylous milky in lymphatic obstruction, infective effusions are cloudy doe to cellular and fibrinous elements.