Oedema Flashcards
What is the definition of oedema?
Excessive accumulation of fluid within the interstitial space, outside the vascular system.
What is anasarca?
Generalised and severe oedema.
What are the 4 Starling’s forces?
- Forces acting on a capillary bed that govern the exchange of fluid between the capillary and interstitial fluid.
- These forces determine the direction of net water movement and the rate of movement.
- Hydrostatic pressure in the capillary (Pc)
- Hydrostatic pressure in the interstitium (Pi)
- Oncotic pressure in the capillary (pc)
- Oncotic pressure in the interstitium (pi)
What is the main contributor to oncotic pressure?
Albumin
What are the causes of low albumin?
- Liver disease
- Nephrotic syndrome
- Malabsorption
- Protein losing enteropathy
What are the approximate Starling’s forces in systemic capillaries (mmHg) at the arteriolar end and at the venous end?
In which direction does water move relative to the interstitium at the arterial end and at the venous end of the capillary?
- Net water movement into the interstitium at the arterial end of the capillary.
- Net water movement from the interstitium at the venous end of the capillary.
How does oedema arise?
- Oedema cana arise beause of:
- Localised or generalised disruption of these (hydrostatic and oncotic) forces
- Problems with lymphatic drainage
Describe the pathophysiology of oedema formation.
- Can occur by the following mechanisms:
- Reduction in plasma oncotic pressure
- Increase in capillary wall permeability
- Increase in venous hydrostatic pressure
- Lymphatic blockage
- If oedema formation was dependant on Starling’s forces alone, then there should be no net increase in fluid volume and therefore weight gain.
- There has to be expansion of the extracellular volume.
- In most cases of generalised oedema, the kidneys avidly retain salt and water.
List some of the causes of oedema.
- Infection / trauma - capillary leak.
- DVT / venous obstruction - increased venous hydrostatic pressure.
- Lymphatic obstruction - damage to lymphatic (radiotherapy).
- Drugs - CCB (increased capillary pressure).
- Idiopathic - oedema in women in the absence of another cause.
- Congestive cardiac failure - increased venous hydrostatic pressure, reduction in CO, renal salt and water retention.
- Cirrhosis - reduced oncotic pressure. Peripheral vasodilation and reduced arterial filling, renal salt and water retention.
- Nephrotic syndrome - avid salt and water retention, decrease in plasma oncotic pressure.
Which conditions predispose an individual to developing oedema?
- Diabetes
- Heart / liver / renal disease
- Cancer surgery or radiation therapy
- Chronic alcohol abuse
- Hypercoagulable disorders / previous DVT / immobilisation or recent surgery
Which drugs commonly cause oedema?
- Calcium channel blockers
- NSAIDs
- Oestrogens
- Thiazolidinediones (glitazones)
- IV fluids
What are the different possible distributions of oedema?
What are the possible features of oedema?
What should the clinical examination of an oedematous patient include?
Also include weight
How is proteinuria quantified?
Describe the pathophysiology, pathology and aetiology of nephrotic syndrome.
- Nephrotic syndrome is always due to glomerular disease.
- Tubular diseases can cause proteinuria but not to this extent.
- Glomeruli can be damaged in diseases of the kidney (glomerulonephritis) or in systemic diseases that affect the kidney.
- Classically described as a consequence of reduction in plasma oncotic pressure.
- Intrarenal sodium retention in collecting duct.
- Increase in capillary permeability.
- Reduction in effective circulating volume leads to reduced CO which leads to ECF expansion.
What are the complications of nephrotic syndrome?
