Difference between revisions of "Oedema"

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{{review}}
 
 
{{toplink
 
|linkpage =General Pathology
 
|linktext =General Pathology
 
|maplink = General Pathology (Content Map)
 
|pagetype =Pathology
 
|sublink1=Circulatory Disorders - Pathology
 
|subtext1=CIRCULATORY DISORDERS
 
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<br>
 
 
==Introduction==
 
==Introduction==
 
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Oedema is NOT a disease; it is the sign of a disease state.   
* Oedema is NOT a disease.
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* Oedema is defined as :'''"The swelling of tissues resulting from accumulation of excess fluid in the intercellular tissue spaces and serous cavities."'''
**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.
 
* Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
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** '''Lungs'''.
 
** '''Lungs'''.
  
==Local oedema==
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==[[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).
 
 
 
====[[Lungs Circulatory - Pathology#Pulmonary oedema|Pulmonary oedema]]====
 
 
 
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
 
*# Normal "push-pull" mechanism at capillary level.
 
*# Efficient lymphatic drainage by rhythmic pumping action near airways.
 
*# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
 
*#* Unlike the capillary basement membrane, which is relatively permeable.
 
 
 
=====Pathogenesis=====
 
 
 
# The pumping efficiency of the lymphatics is exceeded.
 
# Fluid accumulates in connective tissue adjacent to airways.
 
# The alveolar walls fill with fluid.
 
# The alveoli abruptly and severely fill with fluid.
 
#* Associated with the disintegration of alveolar epithelial junctional complexes.
 
 
 
 
 
=====Haemodynamic type=====
 
 
 
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
 
** I.e. is due to elevated pulmonary venous pressure.
 
* Potentially reversible.
 
* Causes:
 
*# '''Cardiogenic'''
 
*#* Usually left ventricular failure.
 
*#* Also occurs with cardiac overload due to valvular disease.
 
*# '''Mechanical'''
 
*#* Large primary pulmonary tumours.
 
*#* Severe metastatic disease.
 
*#* Granulomatous infections may raise pulmonary venous pressure.
 
*# '''Neurogenic'''
 
*#* Seizures or CNS disorder.
 
*#* Rare in domestic species.
 
 
 
=====Permeability type=====
 
 
 
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
 
* Irreversible.
 
* Causes:
 
*# '''Toxins'''
 
*#* Bacterial
 
*#** [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']]
 
*#** [[:Category:Pasteurella and Mannheimia species|''Pasteurella'']]
 
*#** [[:Category:Staphylococcus species|''Staphylococcus'']]
 
*#* Chemical
 
*#** Paraquat.
 
*# '''Aspiration/inhalation'''
 
*#* Gastric contents (low pH)
 
*#* Smoke.
 
*#* Excess ozone.
 
*#* Oxygen.
 
 
 
* There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
 
** E.g. in Adult Respiratory Distress Syndrome (ARDS).
 
 
 
==General oedema==
 
 
 
* General oedema involves subcutaneous and tissue spaces/body cavities.
 
* Indicative of severe upset of overall body fluid balance.
 
** Usually one or more vital organ system is abnormal.
 
* Requires one or more of the following conditions:
 
*# General increase in arteriolar hydrostatic pressure.
 
*# Decrease in osmotic pressure of blood.
 
*# Increase in tissue fluid osmotic pressure.
 
*#* E.g. sodium retention in renal disease.
 
*# Increased capillary permeability.
 
*#* E.g. due to hypoxic damage.
 
  
===Types of General Oedema===
 
  
====Cardiac oedema====
+
==[[General Oedema|General oedema]]==
 
 
* Seen in heart failure.
 
** Shows that cardiac output fails to meet the demands of the tissues throughout the body.
 
** Left-side failure gives pulmonary congestion.
 
*** Leads to pulmonary oedema.
 
** Right-side failure gives systemic congestion.
 
*** Leads to generalised oedema.
 
* Chronic venous congestion develops when cardiac output fails to keep pace with venous return to the heart.
 
* Fluid balance is further complicated by secondary renal impairment.
 
** Sodium is retained, triggering the renin-aldosterone loop with further sodium retention.
 
 
 
====Renal oedema====
 
 
 
* Kidney malfunction induces oedema as a consequence of deranged sodium and water handling.
 
** There is often secondary cardiac involvement.
 
*** Due to via renin effect on heart and myocardial depressant factor.
 
* Causes:
 
*# '''Acute glomerulonephritis'''
 
*#*  Reduction in glomerular filtration rate results in systemic hypertension and retention of excess sodium and water.
 
*# '''Nephrotic syndrome'''
 
*#* A  glomerular filtration defect gives selective heavy loss of plasma proteins (especially albumin)
 
*#** Reduction of plasma osmotic potential results in oedema.
 
*# '''Acute renal tubular necrosis'''
 
*#*  Tubules can no longer selectively reabsorb sodium and other electrolytes. 
 
*#** Water retention with the sodium and urea produces oedema.
 
*# '''Fibrosing glomerulonephritis'''
 
*#* Causes systemic hypertension and secondary cardiac failure with oedema.
 
 
 
====Protein-losing enteropathies====
 
 
 
* Mucosal damage leads to loss of ability to absorb and retain proteins. 
 
** Plasma proteins, especially albumin are lost.
 
*** Circulating plasma proteins area therefore reduced, leading to oedema.
 
* E.g.
 
** Johne's disease in cattle and sheep.
 
** Ulcerative colitis or regional enteritis in dogs.
 
* For more on protein-losing enteropathies, see [[Protein Losing Enteropathy|Protein-Losing Diseases]].
 
 
 
====Hepatic oedema====
 
 
 
* Associated with severe [[Liver - Anatomy & Physiology|liver]] damage.
 
** Liver damage may be:
 
*** '''Actue'''
 
**** E.g. due to acute fascioliasis or canine viral hepatitis.
 
**** Lymphatics and blood vessels of the [[Liver - Anatomy & Physiology|liver]] and [[Peritoneal cavity - Anatomy & Physiology|peritoneal caivity]] are damaged.
 
***** Results in "overflow" of fluid into the [[Peritoneal cavity - Anatomy & Physiology|peritoneal cavity]]. 
 
**** Additionally, hepatocyte damage may result in inadequate inactivation of aldosterone.
 
***** Increases sodium retention giving further water accumulation in the abdomen
 
*** '''Chronic'''
 
**** E.g. metastatic neoplasia or  fibrosing hepatopathy (cirrhosis).
 
**** Failure to produce plasma proteins leads to osmotic imbalance in the peripheral circulation. 
 
**** This is seen as subcutaneous oedema.
 
***** E.g. "bottle jaw".
 
  
 
==Composition of oedema fluid==
 
==Composition of oedema fluid==
 
 
* Inflammatory oedema which produces an exudate.
 
* Inflammatory oedema which produces an exudate.
 
**  This is a protein rich fluid containing many inflammatory cells.
 
**  This is a protein rich fluid containing many inflammatory cells.
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** '''Ventral subcutaneous oedema'''
 
** '''Ventral subcutaneous oedema'''
 
* Seen in heart failure in horses and cattle.
 
* Seen in heart failure in horses and cattle.
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[[Pulmonary Oedema]]
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[[Category:Circulatory Disorders - Pathology]]
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[[Category:Cardiology Section]]

Latest revision as of 17:00, 15 October 2013

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.


Pulmonary Oedema