Tissue Fluid Formation and Oedema Leicester Warwick Medical School Tissue Fluid Formation and Oedema Dr. Kevin West kpw2@le.ac.uk Department of Pathology

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

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

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

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

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

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

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

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

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

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)

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

Balance Sheet - Arterial 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 - Venous Outward Inward 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)

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

Oedema Hydrostatic pressure Oncotic pressure Endothelial integrity Lymphatic integrity

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

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

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

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

Lymphatic Obstruction Tumours Fibrosis Inflammation Surgery Congenital abnormality

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

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

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

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

Pulmonary Oedema

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

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

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

Pleural Effusion

Pericardial Effusion

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

Superior Vena Cava Obstruction