Small proteins contained in the plasma are normally filtered by the glomerulus, but they never appear in the urine. how do you think they are removed from the fluid in the lumen of the nephron? defend your answer. in glomerulonephritis, a condition affecting the ability of glomeruli to filter blood, proteinuria (protein found in the urine) is often seen. one of the causes of glomerulonephritis is high blood pressure. how might high blood pressure lead to proteinuria?