Clearance

is a term which describes the amount of plasma entering the kidneys per minute that has been cleared of a substance

what is a marker susbtance used to determine GFR? Why is it used?

INULIN

it is used because

It is freely filtered, not reabsorbed and not secreted. The amount that crosses into the tubule is determined by the glomerular filtration rate and the plasma concentration. Inulin is infused into the patient and, since nothing happens to it once it has crossed into the tubule, the amount that crossed can be found by finding the amount that appears in the urine.

to calculate GFR using INULIN you need 3 things

Urine conc

urine flow rate

Plasma concentration

what is creatinine used for?

it is more commonly used in clinical practice to measure a patient’s GFR. Creatinine is a by-product of muscle activity with a constant concernation in the blood. it is usually used as part of the U&E urea and electrolyte screen for patients in the UK.