What is Glomerular colloidal osmotic pressure?

During the process of ultrafiltration,the afferent arteriole feeds into the glomerulus, providing the blood for the glomerular capillaries. The blood is filtered so finely that all the constituents are passed onto the lumen of bowman's capsule except the protein present in the plasma.In capillaries the hydrostatic pressure is opposed by osmotic pressure of plasma protein in glomerulus. These unfiltered proteins in glomerulus acts like colloid & the pressure is known as colloidal osmotic pressure.