2. Renal Physiology Flashcards
What does the glomerular filtration rate (GFR) measure?
Renal function
What is the most accurate way of measuring the GFR?
Injecting a radioactive tracer
technetium Tc99
Creatinine clearance is routinely used to measure kidney function.
True or False?
FALSE serum creatinine (creatinine levels in blood rather than in urine)
Why is creatinine used to measure kidney function?
Creatinine is released by muscle at a constant rate.
It is removed by the kidneys, therefore an accumulation points towards a kidney disease.
How is eGFR calculated?
Sex
Age
Ethnicity
Serum creatinine
What does eGFR <10 mean?
Less than 10% kidney function.
Dialysis is needed.
In kidney disease, the failure to reabsorb bicarbonate is associated with which part of the nephron?
Proximal convoluted tubule
Where do loop diuretics act?
Ascending loop of Henle.
Inhibit Na/Cl/K reabsorption
Where does aldosterone act?
Cortical collecting duct
What is the function of Antidiuretic hormone (ADH) and where does it act?
↑ water reabsorption
Medullary collecting duct
(below cortical collecting duct)
What value is plasma osmolality maintained at?
285 mOsm/L
What is normal daily urine output?
1.5 - 2 L of urine
What is the counter current mechanism in the kidneys used for?
Water reabsorption to maintain blood volume + pressure.
High concentration gradient in the medulla achieves this.
What does ‘insensible loss’ refer to in terms of the fluid balance?
sweating
respiration
faeces
What hormones are released in states of stress and fluid loss to prevent dehydration?
ADH = ↑ water channels inserted in collecting duct Renin = ↑ Na reabsorption and vasoconstriction
