Edema is the accumulation of fluid in the interstitial spaces of tissues. It occurs when there is increased hydrostatic pressure forcing fluid out of blood vessels or decreased plasma oncotic pressure pulling fluid back into blood vessels. The two main types of edema fluid are transudate, which is low in protein, and exudate, which is high in protein due to increased vascular permeability. Common causes of edema include increased venous pressure from conditions like heart failure or DVT, reduced plasma proteins from liver or kidney disease, lymphatic obstruction, sodium and water retention by the kidneys, and increased vascular permeability during inflammation.

1. EDEMA
Ikram Ullah
M.Phil MLSc

3. FLUID DISTRIBUTION
 60% of lean body weight is water
 2/3 is intracellular
 1/3 is extracellular (mostly interstitial)
 5% of total body water is in blood plasma

4. EDEMA
 Edema is an accumulation of interstitial fluid within
tissues.
 Extravascular fluid can also collect in body cavities
such as
 the pleural cavity (hydrothorax),
 the pericardial cavity (hydropericardium),
 or the peritoneal cavity (hydroperitoneum, or ascites).
 Anasarca is severe, generalized edema marked by
profound swelling of subcutaneous tissues and
accumulation of fluid in body cavities.

5.  Fluid movement between the vascular and
interstitial spaces is governed mainly by two
opposing forces
 The vascular hydrostatic pressure and the colloid
osmotic pressure
 The outflow of fluid produced by hydrostatic
pressure at the arteriolar end is neatly balanced by
inflow due to the slightly elevated osmotic pressure
at the venular end
 Hence there is only a small net outflow of fluid into
the interstitial space, which is drained by lymphatic
vessels.

6.  Either increased hydrostatic pressure or diminished
colloid osmotic pressure causes increased movement of
water into the interstitium
 This in turn increases the tissue hydrostatic pressure,
and eventually a new equilibrium is achieved.
 Excess edema fluid is removed by lymphatic drainage
and returned to the bloodstream by way of the thoracic
duct

8. TRANSUDATE VS. EXUDATE
 The edema fluid that accumulates owing to increased
hydrostatic pressure or reduced intravascular colloid
typically is a protein-poor transudate
 By contrast, because of increased vascular permeability,
inflammatory edema fluid is a protein-rich exudate

10. CAUSES OF EDEMA
Increased Hydrostatic Pressure:
 Increased hydrostatic pressure leads to accumulation of fluid
in extravascular space (transudate)
 Local increases in intravascular pressure can result from
impaired venous return
 For example, a deep venous thrombosis in the lower
extremity can cause edema restricted to the distal portion of
the affected leg.
 Generalized increases in venous pressure, with resultant
systemic edema, occur most commonly in congestive heart
failure

12. REDUCED PLASMA OSMOTIC PRESSURE
 Condition which albumin is either lost from the circulation
or synthesized in inadequate amounts
 In nephrotic syndrome, damaged glomerular capillaries
become leaky, leading to the loss of plasma proteins
 Results the development of generalized edema
 Reduced albumin synthesis occurs in the setting of
severe liver disease (e.g., cirrhosis) and protein
malnutrition

13. LYMPHATIC OBSTRUCTION
 Impaired lymphatic drainage and consequent
lymphedema
 Usually result from a localized obstruction caused
by an inflammatory or neoplastic condition.
 For example, the parasitic infection filariasis can
cause massive edema of the lower extremity (so-
called elephantiasis)
 Engendering inguinal lymphatic and lymph node
fibrosis.

14. SODIUM AND WATER RETENTION
 Excessive retention of salt (and its obligate associated
water) can lead to edema
 Increasing hydrostatic pressure (due to expansion of the
intravascular volume) and reducing plasma osmotic
pressure

15. o Sodium is retained by the kidney in two conditions.
o Glomerular filtration rate is reduced in acute
glomerulonephritis and renal failure resulting in sodium
and water retention.
o Increased renin angiotensin aldosterone secretion
which causes sodium reabsorption in distal convoluted
tubules accompanied by water reabsorption
(generalized edema)

16. INCREASED VASCULAR PERMEABILITY
o Edema can also result from increased vascular
permeability due to inflammation
o Exudate is the protein rich fluid that is accumulated due to
increased vascular permeability
o Result in increased osmotic pressure in interstitial or
extravascular space due to free passage of plasma protein