Leicester Warwick Medical School

1. Leicester Warwick Medical School Tissue Fluid Formation and Oedema Dr. Kevin West kpw2@le.ac.uk 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. Outward Cap. pressure 30 Negative interstitial fluid pressure 3 Interstitial oncotic pressure 8 Total 41 Inward Plasma oncotic pressure 28 Net out 13 (Filtration pressure) Balance Sheet - Arterial

15. Outward Cap. pressure 10 Negative interstitial fluid pressure 3 Interstitial fluid oncotic presure 8 Total 21 Inward Plasma oncotic pressure 28 Net inward 7 (Reabsorption pressure) Balance Sheet - Venous

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 • inadequate albumin synthesis

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. 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