[1][2] It may also occur in immobile patients (stroke, spinal cord injury, aging), or with temporary immobility such as prolonged sitting or standing, and during menstruation or pregnancy.

[5] An edema will occur in specific organs as part of inflammations, tendinitis or pancreatitis, for instance.

Examples of edema in specific organs: A rise in hydrostatic pressure occurs in cardiac failure.

Most forms of nephrotic syndrome are due to biochemical and structural changes in the basement membrane of capillaries in the kidney glomeruli, and these changes occur, if to a lesser degree, in the vessels of most other tissues of the body.

[10] As well as the previously mentioned conditions, edemas often occur during the late stages of pregnancy in some women.

This is more common with those of a history of pulmonary problems or poor circulation also being intensified if arthritis is already present in that particular woman.

Women who already have arthritic problems most often have to seek medical help for pain caused from over-reactive swelling.

This condition is usually treated with diuretics; otherwise, the water retention may cause breathing problems and additional stress on the heart.

[13] Phlebetic lymphedema (or phlebolymphedema) is seen in untreated chronic venous insufficiency and is the most common type of edema (approx.

The lymphatic system slowly removes excess fluid and proteins from the veins in the lower legs towards the upper body; however, as it is not as efficient as an unimpaired circulatory system, swelling (edema) is visible, particularly in the ankles and lower leg.

The chronic increased fluid in the lymphatic system and capillary hyperpermeability causes an inflammatory response which leads to tissue fibrosis of both veins and lymphatic system, opening of arteriovenous shunts, all of which then worsens the condition in a vicious cycle.

[17] Muscle action is needed not only to keep blood flowing through the veins but also to stimulate the lymphatic system to fulfil its "overflow" function.

[21][22][23] Six factors can contribute to the formation of edema:[24] Generation of interstitial fluid is regulated by the forces of the Starling equation.

As a result, the colloidal or oncotic pressure of the higher level of protein in the plasma tends to draw water back into the blood vessels from the tissue.

[citation needed] Another set of vessels known as the lymphatic system acts like an "overflow" and can return much excess fluid to the bloodstream.

Peripheral pitting edema, as shown in the illustration, is the more common type, resulting from water retention.

It can be caused by systemic diseases, pregnancy in some women, either directly or as a result of heart failure, or local conditions such as varicose veins, thrombophlebitis, insect bites, and dermatitis.