Difference between revisions of "Oedema"

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==[[Local Oedema|Local oedema]]==
 
==[[Local Oedema|Local oedema]]==
* Local oedema is the local accumulation of excess interstitial fluid.
 
* Caused by disturbance of the balance betwen fluid extravasation and resorption at the level of the capillaries.
 
** '''Outwards Forces''' - arteriolar
 
*** Vasuclar hydrostatic pressure - 35 mmHg
 
*** Interstitial osmotic pressure - 3 mmHg
 
** '''Inwards forces''' - venular
 
*** Plasma protein osmotic pressure - 25 mmHg
 
*** Interstitial hydrostatic pressure - 4 mmHg
 
* May be of inflammatory or non-inflammatory origin.
 
  
===Types of Local Oedema===
 
====Inflammatory oedema====
 
* Generated by one or more of the following:
 
*# Increased vascular permeability
 
*# Increased arteriolar blood pressure
 
*# Breakdown of tissue protein or transfer of plasma proteins into ECF.
 
*#* Results in raised osmotic pressure of tissue fluid.
 
*# Obstruction to lymphatic drainage.
 
*#* Usually by fibrin.
 
 
====Lymphatic oedema====
 
* Results in accumulation of high protein fluid.
 
* May provoke a [[Granulation Tissue|granulation]] or fibrous  tissue response.
 
* Due to:
 
*#  '''Lymphangitis/ lymphadenitis '''
 
*#* [[:Category:Acute Inflammation|Acute inflammation]] of lymphatics/ lymph nodes.  R
 
*#* Caused by stasis in lymphatics and/or bacterial infection.
 
*#* E.g.  “Monday Morning leg” in horses.
 
*# '''Chronic inflammation''' caused by persistent or granuloma-producing bacterial infection.
 
*#* E.g. [[Johne's Disease|Johne's disease]],  [[:Category:Actinobacillus species|actinobacillosis]].
 
*# '''Tumour spread'''.
 
*#* [[Neoplasia - Pathology#Dissemination of Malignant Neoplasia|Metastasis]] of tumour cell plugs lymphatics and nodes
 
*#*  e.g.  mammary carcinoma.
 
*# '''Parasitic migration'''
 
*#* Larvae may be following their normal pathway (e.g. Schistosomiasis), or may be aberrant.
 
 
====Local venous obstruction====
 
* Obstruction to venous drainage may be mechanical or inflammatory-mediated.
 
** Causes raised hydrostatic pressure.
 
** Endothelial permeability increases due to hypoxia.
 
** There may be inflammatory damage.
 
* '''Mechanical obstruction''', e.g.
 
** [[Torsion, Intestinal|Torsions of bowel]]
 
** Misplaced organs.
 
** Pressure from outside vein from adjacent structures.
 
*** [[Neoplasia - Pathology|Tumours]].
 
* '''Venous inflammation  (phlebitis)'''
 
**  May be associated with [[Thrombosis#Introduction|thrombosis]] (thrombophlebitis).
 
 
===="Allergic" oedema====
 
* Results from immediate  (Type I ) or delayed (Type IV) hypersensitivity. 
 
* Vasular permeability is increased due to release of histamine and vaso-dilating substances.
 
* E.g.
 
** Insect stings (immmediate).
 
** Vaccination (delayed).
 
** Food reaction (delayed).
 
 
 
[[Category:Circulatory Disorders - Pathology]]
 
 
 
====[[Pulmonary Oedema|Pulmonary oedema]]====
 
  
 
==[[General Oedema|General oedema]]==
 
==[[General Oedema|General oedema]]==

Revision as of 14:35, 14 February 2011

Introduction

Oedema is NOT a disease; it is the sign of a disease state.

  • Oedema is defined as :"The swelling of tissues resulting from accumulation of excess fluid in the intercellular tissue spaces and serous cavities."
  • Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
  • Excess fluid may accumulate in:
    • Subcutaneous tissue and between muscle.
    • Serous cavities.
      • Depending on the cavity, this has different terms.
        • Thorax - hydrothorax.
        • Pericardium - hydropericardium
        • Abdomen - hydroperitoneum (ascites).
      • Anasarca is when there is generalised body cavity accumulation plus subcutaneous involvement.
    • Lungs.

Local oedema

General oedema

Composition of oedema fluid

  • Inflammatory oedema which produces an exudate.
    • This is a protein rich fluid containing many inflammatory cells.
  • Non inflammatory oedema which produces a transudate.
    • This fluid is low in protein and cells.
  • Transudates and exudates are distinguished by the following criteria:
Criteria Transudate Exudate
Appearance Clear/ pale yellow ("straw coloured") Dark yellow, red or brown. Often cloudy or opaque.
Consistency Thin, serous Viscous
Protein content 0.05 - 0.5%, mainly albumin Usually 2 - 4%
Coagulability No fibrinogen, no coagulation Contains fibrinogen, coagulates
Specific gravity Low (< 1.012) High (1.012 - 1.020) +
Cell content Very low. mesothelial cells, some macropahges and lymphocytes/Monocytes. High. Often macrophages, neutrophils, lymphocyes etc. Depends on cause and chronicity


  • Examples of transudates:
    • Ascites
      • Excessive fluid in abdominal cavity.
    • Hydrothorax
      • Excessive fluid in the thorax.
    • Hydropericardium
      • Excessive fluid in the pericardium.
    • Anasarca
      • Generalised tissue oedema most noticeable in subcutaneous tissues.
    • Ventral subcutaneous oedema
  • Seen in heart failure in horses and cattle.