This pressure drives fluid out of the capillary (i.e., filtration), and is highest at the arteriolar end of the capillary and lowest at the venular end. Depending upon the organ, the pressure may drop along the length of the capillary by 15-30 mmHg (axial or longitudinal pressure gradient).

What causes decreased oncotic pressure?

Reduced oncotic pressure, typically due to hypoalbuminemia, occurs in several diseases such as renal disease where the loss of albumin occurs across the glomerulus (nephrotic syndrome), and common causes may include diabetic nephropathy, lupus nephropathy, amyloidosis, minimal change disease, membranous ...

What happens when oncotic pressure decreases?

In conditions where plasma proteins are reduced, e.g. from being lost in the urine (proteinuria), there will be a reduction in oncotic pressure and an increase in filtration across the capillary, resulting in excess fluid buildup in the tissues (edema).