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Aina Meducci 2012


The following blog posts is not genuinely from my research but through readings and citation from trusted website. I do not own any of the copyright and therefore you may use it at your own risk


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What a day! Pathology seems to be the difficult subject to study, and it is a subject where you need to be extraordinary good in histology and physiology. Plus, when you forgot something what you learned during biology class, u be better say bye2 to pathology!


Ascites (swelling of peritoneal area)

Edema refers to the swelling of a tissue that results from excessive accumulation of fluid within the tissue. Edema can be highly localized as occurs in a small region of the skin subjected to a bee sting. Edema, however, can also comprise an entire limb, specific organs such as the lungs (e.g., pulmonary edema) or the whole body.

General principle of edema

There are two primary fluid compartments in the body between which fluid is exchanged - the intravascular and extravascular compartments.The intravascular compartment contains fluid (i.e., blood) within the cardiac chambers and vascular system of the body. The extravascular system is everything outside of the intravascular compartment. Fluid and electrolytes readily move between these two compartments. The extravascular compartment is made up of many subcompartments such as the cellular, interstitial, and lymphatic subcompartments, and a specialized system containing cerebrospinal fluid in the central nervous system.

The movement of fluid and accompanying solutes between compartments (mostly water, electrolytes, and small molecular weight solutes) is governed by physical factors such as hydrostatic and oncotic forces. These forces are normally balanced in such a manner that fluid volume remains relatively constant between the compartments. If the physical forces or barriers to fluid movement are altered, the volume of fluid may increase in one compartment and decrease in another. In some cases, total fluid volume increases in the body so that both intravascular and extravascular compartments increase in volume. This can occur, for example, when the kidneys fail to excrete sufficient amounts of sodium and water.

When the fluid volume within the interstitial compartment (space between the cells and blood vessels) increases, this compartment will increase in size leading to tissue swelling (i.e., edema). This is what happens when an ankle is sprained and swells. When excess fluid accumulates within the peritoneal space (space between the abdominal wall and organs), this is termed "ascites." Pulmonary congestion, which can occur in heart failure as the left atrial pressure increases and blood backs up in the pulmonary circuit, causes pulmonary edema.

Filtration is the movement of fluid out of the capillary and reabsorption is the movement of fluid back into the capillary. In most capillary systems of the body, there is a small net filtration(typically about 1% of plasma) of fluid from the intravascular to the extravascular compartment. In other words, capillary fluid filtration exceeds reabsorption. This would cause fluid to accumulate within the interstitium (i.e., cause edema) over time if it were not for the lymphatic system that removes excess fluid from the interstitium and returns it back to the intravascular compartment. Therefore, Fluid balance occurs when:

Filtration = Reabsorption + Lymphatic Flow

Circumstances, however, can arise in which net capillary filtration exceeds the capacity of the lymphatics to carry away the fluid (i.e., net filtration > lymph flow). When this occurs, the interstitium will swell with fluid, and thereby become edematous.

capillary fluid filtration and reabsorption

Factors contributed to edema:

  • Increased hydrostatic pressure
  • Reduced oncotic pressure (pressure of plasma protein) in blood
  • Increased tissue oncotic pressure
  • Increased blood vessel permeability (eg Inflammation)
  • Obstruction of lymphatic system
  • Retention of water and sodium in kidney

Classification of edema

1. Subcut edema

Cutaneous edema is referred to as "pitting" when, after pressure is applied to a small area, the indentation persists for some time after the release of the pressure. Peripheral pitting edema, as shown in the illustration, is the more common type, results from water retention. It can be caused by systemic diseases, pregnancy in some women, either directly or as a result of heart failure, or local conditions such as varicose veins, thrombophlebitis, insect bites, anddermatitis.

Non-pitting edema is observed when the indentation does not persist. It is associated with such conditions as lymphedema, Lipoedema and myxedema.

2. Generalize edema

Causes of edema which are generalized to the whole body can cause edema in multiple organs and peripherally. For example, severe heart failure can cause pulmonary edema, pleural effusions, ascites and peripheral edema.

3. Organ specific

Edema will occur in specific organs as part of inflammations, tendonitis or pancreatitis, for instance. Certain organs develop edema through tissue specific mechanisms.

Examples of edema in specific organs:

  • Cerebral edema is extracellular fluid accumulation in the brain. It can occur in toxic or abnormal metabolic states and conditions such as systemic lupus or reduced oxygen at high altitudes. It causes drowsiness or loss of consciousness.

  • Pulmonary edema occurs when the pressure in blood vessels in the lung is raised because of obstruction to remove blood via the pulmonary veins. This is usually due to failure of the left ventricle of the heart. It can also occur in altitude sickness or on inhalation of toxic chemicals. Pulmonary edema produces shortness of breath. Pleural effusions may occur when fluid also accumulates in the pleural cavity.

  • Edema may also be found in the cornea of the eye with glaucoma, severe conjunctivitis or keratitis or after surgery. It may produce coloured haloes around bright lights.

  • Edema surrounding the eyes is called periorbital edema or eye puffiness. The periorbital tissues are most noticeably swollen immediately after waking, perhaps due to the gravitational redistribution of fluid in the horizontal position.

  • Common appearances of cutaneous edema are observed with mosquito bites, spider bites, bee stings (wheal and flare), and skin contact with certain plants such as Poison Ivy orWestern Poison Oak,the latter of which are termed contact dermatitis.

  • Another cutaneous form of edema is myxedema, which is caused by increased deposition of connective tissue. In myxedema (and a variety of other rarer conditions) edema is due to an increased tendency of the tissue to hold water within its extracellular space. In myxedema this is because of an increase in hydrophilic carbohydrate-rich molecules (perhaps mostly hyaluronan) deposited in the tissue matrix. Edema forms more easily in dependent areas in the elderly (sitting in chairs at home or on aeroplanes) and this is not well understood. Estrogens alter body weight in part through changes in tissue water content. There may be a variety of poorly understood situations in which transfer of water from tissue matrix to lymphatics is impaired because of changes in the hydrophilicity of the tissue or failure of the 'wicking' function of terminal lymphatic capillaries.

  • In lymphedema abnormal removal of interstitial fluid is caused by failure of the lymphatic system. This may be due to obstruction from, for example, pressure from a cancer or enlarged lymph nodes, destruction of lymph vessels by radiotherapy, or infiltration of the lymphatics by infection (such as elephantiasis). It is most commonly due to a failure of the pumping action of muscles due to immobility, most strikingly in conditions such as multiple sclerosis, or paraplegia. Lymphatic return of fluid is also dependent on a pumping action of structures known as lymph hearts. It has been suggested that the 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 heart action.

  • Hydrops fetalis is a condition of the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments.

Treatment of edema

Reduce salt (sodium) in diet — Sodium, which is found in table salt, can worsen edema. Reducing the amount of salt consumed can help to reduce edema.

Diuretics — Diuretics are a type of medication that causes the kidneys to excrete more water and sodium, which can reduce edema. Diuretics must be used with care because removing to much fluid too quickly can lower the blood pressure and impair kidney function.

In heart failure patients, improving cardiac output by using cardiostimulatory or vasodilators drugs reduces venous and capillary pressures, thereby decreasing filtration and promoting reabsorption of fluid within tissues.

Sources: Edema: Wikipedia, CV Physiology: tissue edema, edema (swellling) www.uptodate.com

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