List the reasons a person may have pitting edema and when appropriate give an underlying pathological cause.

Pitting edema is a result of fluid retention and is caused by proteins spilling out into the interstitial spaces of cells instead of staying in the vasculature (vessels) where they belong.

A common sign of right sided heart failure. When blood gets pumped into the right atria/ventricle it is weak and cannot pump all the blood through sufficiently so there is a back up of blood (like a traffic jam) into the rest of the body, causeing edema.

Also common in renal failure because the kidney cannot sufficiently rid the body of its excessive waste products and protein via urine (which is what healthy kidneys do).