Edema

Is edema normally located in a specific area or generalized?

Usually localized Infrequently it affects most or all of the body. This is referred to as "generalized edema"

Which is more serious normally, the edema or the underlying cause of edema?

The underlying cause

How is edema fluid normally removed from the body?

Through the lymphatics

What can persistent edema cause?

Tissue fibrosis

Does decreased osmotic pressure create transudate or exudate fluid?

Transudate

Does increased hydrostatic pressure make transudate or exudate fluid?

Transudate

Does lymphatic obstruction create transudate or exudate fluid?

Transudate

What is transudate and how is it characterized?

Transudates occur when fluid accumulates without increased vascular permeability and are characterized by clear fluid and low protein concentration.

True or False: When hydrostatic pressures and intravascular colloid osmotic pressure become off balanced edema ensues

True!

What percentage of the body's total body weight is water?

Up to 2/3s

What are the four major causes of edema?

*Increased hydrostatic pressure *Increased vascular permeability *Decreased intravascular oncotic pressure *Lymphatic obstruction

What are the two major reasons for edema that cause transudate formation?

*Increased vascular pressure *Decreased colloid osmotic pressure

What are three reasons for increased vascular permeability?

*Vasculitis *Trauma *Anoxia

What drives fluid out of vessels (what force)?

Mostly hydrostatic pressure - Blood pressure within the vessel is the chief factor that tends to drive fluid out of the capillaries.

What holds fluid within the blood vessels?

Mostly intravascular colloidal osmotic pressure - Also known as oncotic pressure, it refers to protein content. If protein within the blood is high, it will hold fluid in the vessel, if protein is very low, fluid moves out into the interstitium, super duper easy-like.

Is edematous tissue normally red?

No! Not unless hyperemia is present

How do lymphatics present in edematous tissue?

Lymphatics are often distended

What are the characteristics of exudates?

1. High (>2.5 g/dL) protein content, including fibrinogen 2. Numerous cells, especially leukocytes

What are the four main causes of edema?

1. Increased hydrostatic pressure 2. Increased vascular permeability 3. Decreased colloidal osmotic pressure of plasma 4. Lymphatic obstruction

What are the main features of transudate (proteins, cells, etc.)

1. Low protein content <2.5 g/dL 2. Few cells- most of the cells present are mesothelial cells and not leukocytes 3. Low fibrinogen

What is the percentage breakdown of water in regards to intracellular, interstitial and intravascular?

67% intracellular 25% interstitial 8% intravascular

What is transudate?

Accumulation of fluid due to a hydrostatic imbalance between the intravascular and extravascular compartments despite normal vascular permeability

What is an exudate?

Accumulation of fluid due to increased vascular permeability

What is the effect of Angiotensin II on the kidneys?

Adrenal cortex releases aldosterone which increases salt and water retention --> elevates BP

What is anasarca?

Anasarca is a term that means general edema (like of the whole body!) but in common usage, this term is really only used for fetuses that have whole-body edema

How does edema present upon postmortem examination?

At postmortem examination, edema is recognized by the presence of clear or yellow-tinged fluid that distends loose connective tissues or accumulates in body cavities such as the peritoneal, pleural, or pericardial spaces. The fluid may flow upon cutting through the tissue or if the vessels were damaged sufficiently that clotting proteins accompanied the fluid, it may form a lemon jello-like clot.

Other than location, what other way can you classify edema and what are the two categories?

Based on the composition of the fluid- edema fluid consists primarily of water but also contains variable amounts of protein, leukocytes and erythrocytes Transudate Exudate

What is the effect of Angiotensin II on blood vessels?

Blood vessels vasoconstrict --> elevates BP

Does increased hydrostatic pressure create localized or general edema?

Can be either depending on the situation!

Does increased vascular permeability cause localized or general edema?

Can be either!

What can cause a decrease in serum albumin?

Capillary blood contains a decreased quantity of colloids (protein) due to either decreased hepatic synthesis of these proteins or increased protein loss through the kidney or gastrointestinal tract

What is the normal color of transudate and why?

Clear and colorless This is due to the relative absence of protein and cells

How does edematous tissue feel to the touch?

Cool to the touch when inflammation is not present If there is inflammation involved there will be some heat

How does trauma result in edema?

Damage to the endothelial cell walls allows proteins/cells to exit

Where does fluid normally accumulate in right sided heart failure?

Depending on the species of animal, the edema fluid tends to accumulate within the: *Peritoneal cavity (ascites; dog) *The pleural cavity (hydrothorax) *The subcutaneous tissues of the ventral body (e.g., "brisket edema"; cattle) *The intermandibular area ("bottle jaw"; sheep).

Describe the basic outline of the RAAS system.

Drop in blood pressure causes the kidneys to release renin --> Renin cleaves Angiotensinogen (produced in the liver) into Angiotensin I --> Angiotensin I is cleaved by ACE (found in the lungs) to form Angiotensin II

What is the effect of edema on the larynx?

Edema can cause upper airway occlusion and death from asphyxia.

What is hydropericardium?

Edema fluid in the pericardial sac

What is hydroperitoneum and what is another name for it?

Edema fluid in the peritoneal cavity Ascites

What is hydrothorax?

Edema fluid in the thoracic cavity

What is hydrocephalus?

Edema fluid in the ventricles of the brain

What is the fate of edema fluid?

Edema fluid is removed primarily by lymphatic vessels. Chronic edema may be organized by fibrous connective tissue.

How does edema appear grossly?

Edema is recognized as fluid within body cavities and/or by soft, doughy, usually cool and non-painful tissue distention that pits on pressure.

How does edema appear microscopically?

Edema is recognized by separation of normal tissue elements by clear or pink material, and by dilation of lymphatics.

What is the clinical significance of edema?

Edema may cause clinical signs and death by exerting pressure on vital structures.

How does anoxia cause edema?

Endothelial cells, like all other cells, require oxygen to function normally. When adequate oxygen is not present, they fail to create a tight seal and colloids leak between endothelial cells and into and through the vessel wall.

Why does transudate have low fibrinogen?

Escape of significant quantities of fibrinogen from blood vessels requires vascular damage

Does increased vascular permeability create transudate or exudate fluid?

Exudate

What is the importance of knowing the difference between transudate and exudate?

Exudate is much worse, it means there is something harmful hitting the walls of the vessels and inflammation is occurring

What is exudate and how is it characterized?

Exudates occur when vessels are damaged and leaky and are characterized by turbid fluid, high protein concentrations, and high total nucleated cell counts (TNCC).

What is the effect of persistent edema?

Fibrosis of tissues

What is the result of hypoproteinemia?

Fluid and crystalloids fail to be reabsorbed at the venous end of the capillary and accumulate in the interstitium as edema.

Where does distended tissue tend to collect on the body and why?

Fluid tends to accumulate ventrally due to gravity

Does decreased osmotic pressure cause localized or general edema?

Generalized

How does edema look microscopically/histologically?

Histologically, in H&E sections, edema is seen as separation of tissue elements by spaces that are either clear (if the edema is protein-poor) or pink (if the edema fluid contains considerable protein) in H&E-stained sections. Lymphatics may be visibly dilated too

What causes lymphangiectasia?

Lymphangiectasia is usually due to lymphatic obstruction by tumor cells or lymphatic compression by a bandage wrapped too tightly around a leg

What is the result of left sided heart failure in regards to edema?

In left sided heart failure blood pools in the left atrium, impeding venous return from the lungs and causing pulmonary congestion. The increased hydrostatic pressure within the pulmonary vasculature causes pulmonary edema.

What is the pathogenesis of liver disease with regards to edema?

In liver disease, there is decreased production of albumin and so the plasma colloidal osmotic pressure decreases and edema occurs.

How does lymphatic obstruction cause edema?

In lymphatic obstruction, these tissue fluids don't get drained and they accumulate in the interstitium as edema.

What is the pathogenesis of renal/GI disease in regards to edema?

In these diseases, hypoproteinemia occurs due to loss of protein through urine (protein-losing nephropathy) or feces (protein-losing enteropathy).

Out of the four reasons for edema, which one contributes to exudate formation?

Increased vascular permeability (holes/insults to the blood vessels)

What is the effect of Angiotensin II on the brain

Increases thirst and drinking --> elevates BP

How is edema produced by increased vascular permeability?

Injury to vascular walls allows leakage of fluid, protein, and cells, and causes edema. Endothelial cell damage results in increased capillary permeability to fluid, crystalloids, and colloids. The increase in colloids within the interstitium reduces reabsorption of fluid at the venous end of the capillary. These colloids are eventually drained away by the lymphatics.

What is lymphangiectasia?

It means "lymph-vessel-dilation", and is the lymphatic equivalent of congestion

Why does transudate have low protein/cells?

Leakage of materials as large as proteins and cells from vessels requires some degree of vascular damage

How do you name edema of the body?

Localize where the edema is and use the prefix "hydro". Sometimes "hydrops" is used in a similar manner

Does lymphatic obstruction cause localized or general edema?

Localized (normally)

What is the effect of left sided heart failure in regards to the kidneys?

Reduced cardiac output due to left sided heart failure also decreases blood supplied to the kidneys, creating a situation that is critically involved in the progression of congestive heart failure. Reduced renal blood flow induces secretion of renin by cells within the juxtaglomerular complex. Then there is a whole cascade which leads to higher blood pressure.

What is the cause of decreased intravascular osmotic pressure?

Reduction in serum albumin decreases intravascular oncotic pressure and causes edema

What is the result of right sided heart failure in regards to edema?

Right sided heart failure results in pooling of blood in the right atrium and vena cava. The resultant impedance of venous return to the heart increases hydrostatic pressure within the general body vasculature and results in edema

What is the effect of edema on the lungs?

Severe pulmonary edema would have a similar detrimental influence on oxygen availability.

What is edema?

The accumulation of abnormal quantities of water in interstitial tissues and/or body cavities.

What are the causes of exudates?

Usually, exudates occur when infectious agents or toxins either directly damage vessels or cause tissues to produce chemical signals that alter vascular permeability (i.e., bigger holes in the vessels).

How does vascular inflammation cause edema?

Vascular inflammation causes increased vessel permeability so that proteins move into body cavities and/or the tissue interstitial space.

What causes increased intravascular hydrostatic pressure?

Venous obstruction results in increased hydrostatic pressure as blood backs up in the venous system, with leakage of fluid into the interstitial tissues. Capillary permeability is not altered, so significant leakage of colloids (proteins) does not occur unless the pressure increases significantly.

In what situations is edema considered life-threatening?

When edema is present in sites such as the brain, larynx or lungs

What is pitting edema?

When edematous tissue will "pit" (leave an indentation) when pressure is applied All edema is technically pitting edema though

What is the effect of edema on the brain?

When the brain swells there is little room for outward expansion of tissue because the brain is enclosed within the dura mater and the bony skull. Significant intracranial edema then creates enough pressure that nutrients and oxygen can't get through to the neurons