Edema

57 Edema



Astrid Nielssen



1. What is edema?

Edema refers to the excess accumulation of fluid within the tissues of the body. Edema can arise as a result of intracellular fluid accumulation. Most frequently, however, it arises as a result of fluid accumulation within the interstitial space.


2. What can cause edema resulting from intracellular fluid accumulation?

Intracellular fluid accumulation can arise when the normal transmembrane sodium gradient is not maintained. This is due to ionic pump dysfunction, a condition that can result from compromised blood flow to a tissue, or inflammation, a condition that can increase membrane permeability. The increased sodium concentration that arises in the cell draws water into the cell via osmosis and can result in marked cellular swelling.


The edema caused by intracellular swelling is typically nonpitting edema.


3. What can cause edema resulting from extracellular fluid accumulation?

There are two general causes of edema that result from extracellular fluid accumulation: increased capillary filtration and a failure of adequate lymphatic drainage. The most common causes fall into the increased capillary filtration category.


Increases in capillary permeability, hydrostatic pressure, or decreased osmotic pressure can all result in an increased capillary filtration rate. Causes of increased capillary permeability include immune reactions (e.g., histamine release), toxins, bacterial infections, ischemia, and burns. Causes of increased capillary hydrostatic pressure include high venous pressure (e.g., heart failure, venous blockage) or excessive fluid and sodium retention (e.g, acute renal failure). Decreased plasma colloid osmotic pressure results from a decreased plasma protein level, predominantly if albumin is decreased. This can be due to a failure of production (e.g., with hepatic failure) or an increased loss (e.g., with nephrotic syndrome, protein-losing enteropathy, vasculitis) of these proteins.


Edema associated with diminished lymphatic drainage (also called lymphedema) can be either primary or secondary in nature (see question 4). Edema associated with lymphatic obstruction can be especially severe because the proteins that are leaked into the extracellular space have no other means by which to be removed and provide an increased osmotic pull within the interstitium.


The edema caused by interstitial fluid accumulation is typically a pitting edema.

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Jul 31, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Edema

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