Types Of Edema

Types Of Edema

Describe important types of edema. Write in detail.
Answer:

Important Types of Edema

The following are the important types of edema:

• Renal edema
• Cardiac edema
• Pulmonary edema
• Cerebral edema.

Renal Edema

Generalized edema occurs in various diseases of renal origin, i.e. nephritic syndrome, glomerulonephritis, and in acute tubular injury.

Edema Pathogenesis

Edema in Nephrotic Syndrome

As there is persistent and heavy proteinuria occurs in nephrotic syndrome there is hypoalbuminemia which leads to decreased plasma oncotic pressure which causes severe generalized edema. Hypoalbuminemia leads to a fall in plasma volume which activates the rennin angiotensin–aldosterone mechanism which causes retention of sodium and water which persists till albuminuria continues.

Edema in Nephritic Syndrome

This occurs in glomerulonephritis. Nephritic edema occurs due to excessive reabsorption of sodium and water in renal tubules through the renin-angiotensin-aldosterone system.

Edema in Acute Tubular Injury

This occurs following the shock or toxic chemicals which results in gross edema of the body. Damaged tubules lost their capacity for selective reabsorption and concentration of glomerular filtrate which causes increased reabsorption of water and oliguria and edema to occur.

Types of edema

Cardiac Edema

Generalized edema is seen in right-sided heart failure and congestive cardiac failure.

Cardiac Pathogenesis

• Hypovolemia occurs due to reduced cardiac output which leads to stimulation of intrinsic renal and extra-renal hormonal mechanisms along with ADH secretion which causes sodium and water retention with edema.
• Heart failure causes an increase in central venous pressure which gets transmitted to the venous end of capillaries increasing capillary hydrostatic pressure and consequent transudation called as back pressure hypothesis.
• Chronic hypoxia injures the capillary wall leading to increased capillary permeability which causes edema and is known as the forward pressure hypothesis. This is not accepted.
• Cardiac edema depends solely on the edema. In an ambulatory patient, edema occurs in the lower extremities while in bedridden patients it occurs in the sacral and genital areas.

Pulmonary Edema

It occurs from left heart failure. Fluid accumulation occurs in tissue spaces and pulmonary emboli.

Pulmonary Pathogenesis

Pulmonary edema occurs either from elevation of pulmonary hydrostatic pressure or increased capillary permeability.

1. Elevation in Pulmonary Hydrostatic Pressure

In heart failure, there is an increase in the pressure of pulmonary veins which gets transmitted to pulmonary capillaries.

This causes an imbalance between the pulmonary hydrostatic pressure and plasma oncotic pressure so the excessive fluid moves out of pulmonary capillaries inside the interstitium of the lungs.

Collected interstitial fluid gets cleared by lymphatics present around the bronchioles. Since the draining capacity of lymphatics for draining the fluid gets exceeded the excess fluid accumulates in the interstitium.

Elevation of hydrostatic pressure due to high pressure of interstitial edema the alveolar lining cells to break and alveolar air spaces to get flooded with the flid. It is commonly seen in left heart failure, mitral stenosis, pulmonary vein obstruction, thyrotoxicosis, etc.

2. Increased Vascular Permeability

Vascular endothelium and alveolar epithelial cells become damaged leading to increased vascular permeability which causes excessive fluid and plasma proteins leakage inside the interstitium and then in the alveoli.

This is seen in fulminant pulmonary and extrapulmonary infections, shock, radiation injury, etc.

3. Acute High Altitude Edema

People climbing to a high altitude suddenly without halt and without waiting for acclimatization to set in suffer from serious circulatory and respiratory ill effects.

These changes lead to the appearance of edema in the lungs, congestion, and widespread minute hemorrhages. Here anoxia damages the pulmonary vessels.

Pulmonary edema causes

Cerebral Edema

Inside the brain, the blood-brain barrier causes fluid electrolyte exchange.

Cerebral edema is of three types viz:

• Vasogenic edema
• Cytotoxic edema
• Interstitial edema.

Vasogenic Edema

It results due to increased filtration pressure or increased capillary permeability. This edema is prominent at cerebral contusions, infarcts, brain abscesses, and in a few tumors.

Cytotoxic Edema

In this blood-brain barrier is intact and fluid accumulated intracellularly. It occurs due to disturbance in cellular osmoregulation as seen in some metabolic derangements, and acute hypoxia with some toxic chemicals.

Lymphatic edema treatment

Interstitial Edema

It occurs when an excessive fluid crosses the ependymal lining of the ventricles and accumulates in periventricular white matter. It is seen in non-communicating hydrocephalus.