1. Tissue Fluid Formation and Oedema
Leicester Warwick Medical School
Tissue Fluid Formation and Oedema
Dr. Kevin West
Department of Pathology

3. Tissue Fluid Formation - Objectives 1
Control of normal interstitial fluid formation
Definition of oedema
Definition of pleural effusion, pericardial effusion and ascites
Distinction between transudate and exudate

4. Tissue Fluid Formation - Objectives 2
Common causes and mechanisms of development of oedema
Pulmonary oedema - causes and effects
Cerebral oedema - causes and effects

5. Water Major body component 60% male 50% female 3 compartments
intracellular
extracellular interstitial
extracellular intravascular

6. Osmolality
Osmotic pressure related to number of particles of solute
Oncotic pressure describes osmotic pressure exerted by proteins
Effect of oncotic pressure small but significant across capillaries

7. Control of Interstitial Fluid
Hydrostatic pressure
Oncotic pressure
Endothelial integrity
Lymphatic system

8. Interstitial Fluid
Fluid between cells
Derived from capillaries
Solutes similar to plasma except for protein content

9. Movement Of Fluid Across Capillaries
Capillary (hydrostatic) pressure
Interstitial fluid (hydrostatic) pressure
Plasma oncotic pressure
Interstitial fluid oncotic pressure

10. Capillary Pressure
Forces fluid from capillary to interstitium
Arterial end higher than venous end
Arterial approx. 30 mmHg
Venous approx. 10 mm Hg

11. Interstitial Fluid Pressure
Maybe positive or negative
Negative - forces fluid into interstitium
Positive - forces fluid into capillary
Approx. minus 3 mm Hg in loose connective tissue
Higher in denser connective tissue

12. Plasma Oncotic Pressure
Proteins are the only solutes which do not pass freely between plasma and interstitium
Thus it is only proteins which exert a significant osmotic effect across capillary walls
Albumin is the most abundant plasma protein
Approx 28 mm Hg (Albumin = 21.8)

13. Interstitial Oncotic Pressure
A small amount of protein is present in the interstitium
Tends to force fluid out of capillary
Concentration is approx 40 % of that in plasma
Approx 8 mm Hg

14. Balance Sheet - Arterial
Outward
Cap. pressure
Negative interstitial
fluid pressure
Interstitial oncotic
pressure
Total
Inward
Plasma oncotic
pressure
Net out
(Filtration pressure)

15. Balance Sheet - Venous Outward Inward Cap. pressure 10
Negative interstitial
fluid pressure
Interstitial fluid
oncotic presure
Total
Inward
Plasma oncotic
pressure
Net inward
(Reabsorption
pressure)

16. Lymphatic System
The lymphatic system provides a route for the transport of fluids and protein away from the interstitium
System of fine lymphatic channels throughout the body passing via lymph nodes to thoracic duct
Valves ensure one-way flow

17. Oedema
Hydrostatic pressure
Oncotic pressure
Endothelial integrity
Lymphatic integrity

18. Oedema
Definition
An increased volume of interstitial fluid in a tissue or organ
May be localised or generalised (systemic)

19. Causes of Oedema
Raised capillary pressure
Reduced oncotic pressure
Endothelial damage (inflammation)
Impaired lymphatic drainage

20. Raised Capillary Pressure
Cardiac failure
right ventricular failure - systemic oedema
left ventricular failure - pulmonary oedema
congestive cardiac failure - both
Local venous obstruction
deep vein thrombosis
external compression
SVC obstruction

21. Reduced Oncotic Pressure
Renal disease
loss of albumin across glomerulus
Hepatic disease
inadequate albumin synthesis
Malnutrition

22. Lymphatic Obstruction
Tumours
Fibrosis
Inflammation
Surgery
Congenital abnormality

23. Generalised Oedema
Congestive cardiac failure
Right ventricular failure
Renal disease
Liver disease

24. Generalised Oedema Commonly causes swelling of ankles
Swelling may extend higher
Sacral oedema in recumbent patients

25. Right Ventricular Failure
Raised jugular venous pressure also seen
Enlarged liver also common due to congestion (nutmeg liver)

26. Pulmonary Oedema Usually caused by LVF
Raised pressure across pulmonary capillaries
Causes shortness of breath
Due to ischaemic heart disease or hypertension

27. Pulmonary Oedema

28. Congestive Cardiac Failure
Combination of left and right ventricular failure
Common in ischaemic heart disease
Causes systemic and pulmonary oedema

29. Cerebral Oedema Causes increased intracranial pressure
Fatal if left untreated
Generalised in hypoxia, injury
Surrounding other lesions eg tumour, abscess

30. Ascites (peritoneal effusion)
Fluid in Body Cavities
Pleural effusion
heart failure, inflammation, tumour
Pericardial effusion
inflammation, tumour
Ascites (peritoneal effusion)
cirrhosis, heart failure, tumour

31. Pleural Effusion

32. Pericardial Effusion

33. Ascites Most severe cases associated with cirrhosis of the liver
intra-abdominal malignancy

35. Superior Vena Cava Obstruction