In preparation ...
BP and fluid - pic of salt
Extracellular fluid balance is essentaillly a question of salt management. Salt retention and high blood pressure are disturbed very early in many glomerular diseases, but of course they become a problem in all types of kidney disease when GFR drops low enough.
The first sign of excess intravascular fluid, if you have a normal heart, is hypertension. More extreme fluid retention leads to high right atrial pressure, which you assess as jugular venous pressure, then to high left atrial pressure and pulmonary oedema. This of course looks very like heart failure. Be very suspicious of heart failure with high blood pressure - look for a renal contribution. However it is very common for cardiac and renal disease to coexist.
Peripheral fluid collects if sodium retention and volume overload continue, though an average person can accumulate some litres of excess extracellular fluid before this develops. In adults we classically see this at ankles first. Children and young adults may develop ascites before ankle oedema though - as will those with liver disease; and in young people periorbital oedema in the mornings can be more prominent than ankle swelling.
Don't forget that local factors can also cause oedema - venous or lymphatic obstruction, and inflammation, by increasing capillary permeability. Oedema from edrep