Increased interstitial fluid volume.

Edema develops when there is net efflux of fluid from the intravascular space into the interstitial space.
There are of four common mechanisms with edema formation: Increased hydrostatic. pressure, increased membrane permeability, decreased oncotic pressure, and decreased in lymphatic drainage.
Edema may be caused by either increased hydrostatic pressure or reduced oncotic pressure in the blood vessels.
Edema due to increased hydrostatic pressure may be a result of serious cardiopulmonary disease, which reduces glomerular perfusion in the kidney, or to kidney injury or disease which may reduce glomerular excretion of salt and water by the kidney or due to relatively benign conditions such as menstrual-related fluid retention, or as an adverse effect of dihydropyridine calcium channel blockers, which commonly cause swelling of the feet and lower legs.
Edema due to decreased oncotic pressure may be a result of leaking of blood proteins through the glomeruli of an injured kidney or a result of decreased synthesis of blood proteins by the liver.
 The underlying cause of the above mechanisms determines the distribution of the edema.
Vascular or lymph vessel obstruction obstruction typically causes a focal edema, whereas a disorder of albumin production causes a decrease in osmolality due to kidney excretion, or lack of absorption in the gut results in symmetric diffuse edema.
Increased hydrostatic pressure due to heart failure typically  causes distal edema.
Increased plasma volume due to renal sodium retention, can occur in the presence of heart failure or liver disease, and results in symmetric dependent edema.

Fluid retention or swelling, is the build up of fluid in the body’s tissue.

It occurs most commonly in the legs or arms.

Symptoms may include: skin tightness, heaviness and affected joints may be hard to move.

Usually of gradual onset.

May be generalized, or localized.

Causes of edema:

Venous insufficiency,

heart failure,

kidney problems,

low protein levels,

liver problems,

deep vein thrombosis,




prolonged sitting or standing,



A clinical diagnosis.

Clinically more serious if it starts suddenly, or associated with pain or shortness of breath is present.

More common in elderly.

Treatment is based on cause of edema:

If process involves sodium retention, decreased salt intake and a diuretic may be used, elevating the legs and support stockings may be useful for edema of the legs.

Edema may specifically effect specific organs as part of inflammation: tendonitis or pancreatitis.

Pedal edema refers to dependent edema of the legs and is is extracellular fluid accumulation.

Pedal edema may occur in healthy individuals with hypervolemia or maintaining a standing or seated posture for an extended period of time.

Pedal edema can be due to diminished venous return of blood to the heart due to congestive heart failure or pulmonary hypertension, with increased hydrostatic venous pressure or decreased oncotic venous pressure, due to obstruction of lymphatic or venous vessels draining the lower extremity.

The principal cause of edema may be increased capillary filtration or failure of lymphatic drainage, which may be a result of lymphedema, venous hypertension, immobility, obesity, and heart failure.

Certain drugs can cause pedal edema:NSAIDs, amlodipine.

Cerebral edema in the brain involves accumulation of extra cellular fluid and can occur in toxic or abnormal metabolic states and conditions such as systemic lupus or reduced oxygen at high altitudes.

Cerebral edema causes drowsiness, loss of consciousness, and can lead to brain herniation and death.

Pulmonary edema occurs when the pressure in lung blood vessels is increased because of obstruction to the removal of blood via the pulmonary veins.

Pulmonary edema is usually due to failure of the left ventricle of the heart, but can also occur in altitude sickness or on inhalation of toxic chemicals.

Pulmonary edema is associated with shortness of breath and pleural effusions may occur if accumulates in the pleural cavity.

Edema may also be found in the cornea of the eye with glaucoma, conjunctivitis, keratitis or after eye surgery.

Edema that surrounds the eyes is called periorbital edema.

Cutaneous edema is observed with mosquito bites, spider bites, bee stings, and skin contact with certain plants such as poison ivy or western poison oak.

Myxedema is a cutaneous form of edema caused by increased deposition of water into connective tissue.

In myxedema the edema is caused by an increased tendency of the tissue to hold water within its extracellular space because of an increase in hydrophilic carbohydrate-rich molecules deposited in the tissue matrix.

Edema forms more easily in dependent areas.

Estrogens increase body weight in part through changes in tissue water content.

With estrogens the transfer of water from tissues to lymphatics is impaired because of changes in the hydrophilicity of the tissue or failure of the function of terminal lymphatic capillaries.

In lymphedema abnormal removal of interstitial fluid is caused by failure of the lymphatic system: due to obstruction or destruction of lymph vessels by radiotherapy, or infiltration of the lymphatics by infection.

Lymphedema is most commonly due to a failure of the pumping action of muscles.

Edema that occurs in some people following use of aspirin-like cyclo-oxygenase inhibitors such as ibuprofen or indomethacin may be due to inhibition of lymph action.

A rise in hydrostatic pressure occurs in cardiac failure induced edema.

Edema with a fall in osmotic pressure occurs in nephrotic syndrome and liver failure.

Systemic edema is called anasarca.

In rare cases, a Parvovirus B19 infection may cause generalized edema.

Low plasma oncotic pressure is cited the edema of nephrotic syndrome.

Edema may occur before there is any significant proteinuria or fall in plasma protein level.

The nephrotic syndrome is due to biochemical and structural changes in the basement membrane of capillaries in the kidney glomeruli, and these changes occur, if to a lesser degree, in the vessels of most other tissues of the body.

These changes result in increase in permeability that leads to protein in the urine can explain the edema if all other vessels are more permeable as well.

Edema often occurs during the late stages of pregnancy, usually found in the lower part of the leg, usually from the calf down.

Hydrops fetalis is a condition in a baby characterized by an accumulation of fluid in at least two body compartments.

If the heart begins to fail, as in congestive heart failure. the pressure changes can cause very severe water retention: water retention is mostly visible in the legs, feet and ankles, but water also collects in the lungs, where it causes a chronic cough.

Another cause of severe water retention is kidney failure.

In cases of severe protein deficiency, the blood may not contain enough protein to attract water from the tissue spaces back into the capillaries, resulting in edema.

Late pregnancy is commonly associated with swollen legs, feet and ankles.

The edema is partly caused by the weight of the uterus on the major veins of the pelvis.

Water retention in the legs is related to inactivity, as exercise helps the leg veins work against gravity to return blood to the heart.

Extremity muscle activity is required to keep blood flowing through the veins, and it also stimulates the lymphatic draining system.

Fluid retention is seen in long-haul flights, bed-rest, and immobility due to decreased muscle activity.

Medications associated with water retention include: estrogens, non-steroidal anti-inflammatory drugs and beta-blockers.

Premenstrual edema that causes bloating and breast tenderness, is common.

Edema factors:

increased hydrostatic pressure;

reduced colloidal or oncotic pressure within blood vessels;

increased tissue colloidal or oncotic pressure;

increased blood vessel wall permeability

obstruction of lymphatic system;

changes in the water retaining properties of tissues.

Retention of water and sodium by the kidneys raises hydrostatic pressure.

Hydrostatic pressure within blood vessels causes water to filter out into the tissue, leading to a difference in protein concentration between blood plasma and tissue.

The colloidal or oncotic pressure of the higher level of protein in the plasma tends to draw water back into the blood vessels from the tissue.

The rate of leakage of fluid is determined by the difference between the two forces and also by the permeability of the vessel wall to water, which determines the rate of flow for a given force imbalance-Starlings equation.

Most of water leakage occurs in capillaries or post capillary venules, as they have a semi-permeable membrane walls that allows water to pass more freely than protein.

Contribution to the formation of edema is either by an increase in hydrostatic pressure within the blood vessel, a decrease in the oncotic pressure within the blood vessel or an increase in vessel wall permeability.

Grading of edema:

+ Mild: Both feet / ankles

++ Moderate: Both feet

plus lower legs,

hands or lower arms

+++ Severe: Generalized

bilateral pitting edema,

including both feet,

legs, arms and face

Pitting edema is referred to when, after pressure is applied to a small area, the indentation persists after the release of the pressure.

Non-pitting edema: the indentation does not persist,and isassociated with such conditions as lymphedema, and myxedema.

Kwashiorkor is edema associated with malnutrition, an acute form of childhood protein-energy malnutrition characterized by edema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates.

Treatment may also involve use of diuretics, and positioning the affected body parts to improve drainage.

Accumulation of excess fluid in the peritoneal cavity is referred to as ascites, and accumulation of fluid in the pleural cavity is called hydrothorax.

Gross generalized edema referred to as anasarca.

May be localized or generalized in nature.

Hydrostatic pressure in the vascular system and colloid oncotic pressure in interstitial fluid promote fluid movement from the vascular to the extravascular space.

The colloid oncotic pressure contributed by plasma proteins and the hydrostatic pressure in interstitial fluid promote the movement of fluid into the vascular space.

There is a movement of water and diffusible solutes from the vascular compartment at the arteriolar end of capillaries.

Fluid returns from the interstitial space to the vascular compartment at the venous end of the capillary and by lymphatic vessels.

A steady state exists within the intravascular and interstitial compartments with large exchanges between them, but when a an imbalance exists in one of the oncotic or hydrostatic forces a net movement of fluid occurs between the two components of the extracellular space.

Disrupted interstitial fluid homeostasis and typically associated with cardiac, renal, hepatic, venous or lymphatic abnormalities.

Compression therapy can be used to reduce and control chronic edema of the lower extremities.

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