Which is only filtered into renal tubules?

Renal DTPA scan is a process for diagnosis and evaluation of kidney functioning. It involves intravenous administration of radiopharmaceutical material to assess the drainage pattern of kidneys and to find out if any area is not functioning properly. This painless, non-invasive technology has revolutionised the world of medicine. Ref: guyton and hall textbook of medical physiology 12 edition page number: 465,466,467