Oedema can be caused by:

Edema and effusion Disorders that disturb cardiovascular, renal, or hepatic function are often marked by the accumulation of fluid in tissues (edema) or body cavities (effusions). Elevated hydrostatic pressure or diminished colloid osmotic pressure disrupts this balance and results in increased movement of fluid out of vessels. Within tissues the result is edema, and if a serosal surface is involved, fluid may accumulate within the adjacent body cavity as an effusion. Increased Hydrostatic pressure Impaired Venous Return Congestive venous Return Constrictive pericarditis Ascites (liver cirrhosis) Venous obstruction or compression Thrombosis External pressure (e.g. mass) Lower extremity inactivity with prolonged dependency Aeriolar Dilation Heat Neurohumoral dysregulation Reduced plasma osmotic pressure (Hypoproteinemia) Protein- losing glomerulopathies (nephrotic syndrome) Liver cirrhosis (ascites) Malnutrition Protein - losing gastroenteropathy Lymphatic obstruction Inflammatory Neoplastic Postsurgical Postirradiation Sodium Retention Excessive salt intake with renal insufficiency Increased tubular reabsorption of sodium Renal hypoperfusion Increased renin-angiotensin-aldosterone secretion Inflammation Acute inflammation Chronic inflammation Angiogenesis