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Edema

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   CAPTION: Name of Symptom/ Sign:
   Edema
   Classifications and external resources

    ICD- 10   R 60.9
     ICD- 9   782.3
   DiseasesDB 9148
   MeSH       C23.888.277

   Edema (American English) or oedema (British English), formerly known as
   dropsy or hydropsy, is swelling of any organ or tissue due to
   accumulation of excess lymph fluid, without an increase of the number
   of cells in the affected tissue. Edema can accumulate in almost any
   location in the body, but the most common sites are the feet and
   ankles.

Principles

   Edema is the increase of interstitial fluid in any organ. Generally,
   the amount of interstitial fluid is in the balance of homeostasis.
   Increased secretion of fluid into the interstitium or impaired removal
   of this fluid may cause edema.

   Generation of interstitial fluid is regulated by Starling equation of
   Tissue Fluid which states that it depends on the balance of osmotic
   pressure and of hydrostatic pressure across the capillary walls.
   Consequently, anything that increases oncotic pressure outside blood
   vessels (for example inflammation), or reduces oncotic pressure in the
   blood (states of low plasma osmolality, for example cirrhosis) will
   cause edema. Increased hydrostatic pressure inside the blood vessel
   (for example in heart failure) will have the same effect.

   Abnormal removal of interstitial fluid is caused by obstruction of the
   lymphatic system, for example due to pressure from a cancer or enlarged
   lymph nodes, destruction of lymph vessels by radiotherapy, or
   infiltration of the lymphatics by infection such as elephantiasis.

Peripheral edema

   Edema without a modifier usually refers to peripheral or dependent
   edema, the accumulation of fluid in the parts of the body that are most
   affected by gravity. In ambulatory people these are the legs, although
   in those who are bedbound the first manifestation may be sacral edema.
   If severe enough, peripheral edema may progress to involve the
   abdominal or even thoracic wall (this may be referred to as generalized
   edema or anasarca). In particular edema states (e.g. nephrotic
   syndrome, see below), periorbital edema (around the eyes) may be
   present.

   Some phenomena may distinguish different causes of peripheral edema.
   Most peripheral edema is pitting edema - pressing down will lead to a
   shift in the interstitial fluid and the formation of a small pit that
   resolves over seconds. Non-pitting edema may reflect lymphedema, a form
   of edema that develops when the lymph vessels are obstructed.

   Causes of peripheral edema are:
     * high hydrostatic pressure of the veins, leading to poor
       reabsorption of fluid
          + venous obstruction, e.g. deep vein thrombosis (typically
            one-sided)
          + congestive heart failure
          + varicose veins
          + asymmetric compression of thigh and leg (e.g., knee pads,
            tight jeans)
     * low oncotic pressure
          + cirrhosis
          + malnutrition
          + nephrotic syndrome (renal protein loss)
          + epidemic dropsy
     * obstruction of lymph drainage
          + infection
          + cancer
          + fibrosis after surgery
          + filariasis
     * inflammation (active secretion of fluid into the interstitial space
       due to increased membrane permeability by inflammatory mediators):
          + allergic conditions (e.g. angioedema)
          + any other form of inflammation (tumor - or swelling - is one
            of the main characteristics of inflammation)

Organ-specific edema

   Edema of specific organs ( cerebral edema, pulmonary edema, macular
   edema) may also occur, each with different specific causes to
   peripheral edema, but all based on the same principles. Ascites is
   effectively edema within the peritoneal cavity, as pleural effusions
   are effectively edema in the pleural cavity. Causes of edema which are
   generalised to the whole body can cause edema in multiple organs and
   peripherally. For example, severe heart failure can cause peripheral
   edema, pulmonary edema, pleural effusions and ascites.

   Common and usually harmless appearances of cuteneous edema are observed
   with mosquito bites and skin contact with certain plants ( urticaria).

Edema in plants

   Edema in plants is the extended swelling in plant organs caused
   primarily by an excessive accumulation of water.
   Retrieved from " http://en.wikipedia.org/wiki/Edema"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
