Oedema Flashcards
Define edema
- Excessive accumulation of extracellular fluid in the interstitial tissue or body cavity
- Maybe localized or generalized (anasarca
Give types of pericardial effusion
Pleural effusion : Accumulation of fluid in pleural cavity
Pericardial effusion :
Accumulation of fluid in the pericardial cavity ,compromise the ability of the heart to beat
Ascites ; Accumulation of fluid in the peritoneal cavity
Distribution of fluid between vascular compartment and interstitial space depends on :
- Colloid osmotic pressure : proteins draw water into the intravascular space
- Capillary hydrostatic pressure : forces water out of the vessel
- Interstitial hydrostatic pressure : pushes water into the capillary
- interstitial osmotic pressure : it is too insignificant to cause a change ,in ideal situation s
Normal homeostatic depends on
- Intact vessel wall
- Intravascular pressure (hydrostatic pressure) and osmolarity (oncotic pressure ) within physiological ranges
- Changes in vascular volume ,pressure ,protein content or changes in endothelial function affect net movement of water across net movement
Classification of edema : 4 pathogenic mechanisms
- Venous - due to increased intravenous pressure
* Congestive cardiac failure
* Constrictive pericarditis
* Venous obstruction : thrombosis ? compression
*Any cause of fluid retention
+Excessive salt intake with renal insufficiency
+ Cushing syndrome - cortisol causes sodium and fluid retention
1.Cardiac edema mechanism
first mechanism of edema
*Congestion from heart failure > increased hydrostatic pressure in the vein
> Decreased renal blood flow from the lest heart failure causes Na+ retention which water back into intravascular space and increase ECF volume
> Heart failure is associated with pulmonary edema and congestion of the liver
How to test cardiac edema
*Finger pressure over edematous tissue displaces the interstitial fluid and leaves a finger-shaped depression called pitting edema
How to determine venous obstruction
- Unilateral leg edema - thrombus causing venous obstruction resulting in increase in hydrostatic pressure
- Deep vein thrombosis is a serious complication of immobilization and surgery
- Hypoalbuminaemic ( reduced plasma oncotic pressure –Second mechanism of edema
- liver failure eg cirrhosis
- reduced synthesis of albumins > edema
- Protein malnutrition = reduced protein intake
- Increased protein loss
- Protein losing enteropathy
- Nephrotic syndrome (protein is lost in urine)
- Hepatic edema
the third mechanism of edema
- obstruction of the portal venous system
- Manifested by ascites
- The diseased liver has decreased synthesis of albumin > worsen the edema
Lymphatic edema
aetiology of edema
*Tissue drains of fluid by lymphatic ,if obstructed results in edema
-Neoplastic ; infiltration of the lymphatic vessels by tumour eg in breast carcinoma(peau D orange ( looks like orange ) .
edema of skin
Aetiology of edema :
Disruption of the lyphatic system can lead to edema
1.Post surgical eg axillary lymph node dissection for breast cancer ,rare event
2.Post irradiation
firm brawny edema ,non pittity
- Obstruction of lymphatic drainage by filarial parasites( eg wuchecheria bancrofti)
* Lymph node fibrosis in the inguinal region > edema of genetalia and lower limbs - elephantiasis
- Inflammatory - Increased vascular permeability
fourth mechanism
- Endothelial cells separate - chemical mediators
- Protein - rich fluid leaks into interstitium > local swelling
- Dilutes toxins
- fibrin localize damage
- immunoglobulins ,neutrophils and complement neutralize toxins and bacteria
- associated with pain and redness
Acute inflammatory edema
- Exudate at site of inflammation
- Due to increase vascular permeability and increase in hydrostatic pressure
- Hyperemia
Allergic / hypersensitivity edema = angioedema
5th mechanism
*Form of inflammatory edema associated with allergy eg drug ,food
*often seen in skin and mucous membrane
>Increase in vascular permeability and histamine release
> edema of eyelids , lips ,tongue ,larynx and lungs
Clinical features of generalized edema
- Evident after accumulation of at least 5 liters of extra fluid
* Best way to measure generalized edema is weight patient
* Gravitational depends on position of patient
* can be demonstrated by pitting on pressure, takes 1-2 min to recover normal shape of skin
types of edema fluid
- transudate
* Usually straw - coloured often blood stained
* no cells
* protein free fluid
* intact vessel wall - Exudate
* High protein turbid fluid
* contain inflammatory cells
* found from damaged vessel wall
* fibrin clot present
3 types of brain edema
1.3 Vasogenic edema
- BBB is disrupted
- with increased vascular permeability
- Accumulation of fluid in the extracellular space
- associated with tumor
- Cytotoxic edema
* Increase in intracellular edema due to neuronal , glial and endothelial membrane damage
* Brain cells become waterlogged eg cloudy swelling ischemia - Interstitial edema
* In non-communicating hydrocephalus where there is obstruction of flow from the ventricles ,CSF permeates through the ependymal lining of the ventricles into surrounding white matter
Morphology of brain edema
- flattened gyri
- Narrowed sulci
- soft with fluid dripping
- swelling of the brain leads to raised ICP ,if severe l> brain herniation
- can be diagosed by finding papilledema
Pulmonary edema
type of edema
- Seen in
* left ventricular failure ,lung infection ,diffuse alveolar damage ,aspiration pneumonia ,O2 toxicity and hypersensitiity reactions - the lungs are congsted and weigh 32 –3 x their normal weight
- Edema fluid is high in protein content
- Decreased lung volume > breathless and cyanosed
- fluid accumulates in alveolar spaces
- fluid in spaces - > low gaseous exchanges >capillary becomes hypoxic with increased permeability and protein escapes from the vessel
clinically : lungs sound as if air bubbling through water
Renal edema
types of edema
- sodium and water retention > increased hydrostatic pressure
- Nephrotic syndrome - low serum albumin
- Increased vascular permeability
- Increased vascular permeability
- Starts in tissues with loose connective tissue matrix eg peri - orbital
