Renal physiology Flashcards
What 3 hormones do kidneys make?
Renin
Erythropoietin
1, 25 dihydroxyvitamin D, (calcitriol)
What unit is the GFR usually expressed in clinically?
ml/min/1.73m2
What is a normal GFR?
120 ml/min/1.73m2, although above 90 is usually normal
What percentage of cardiac output goes to the kidneys
20%
GFR is estimated by renal clearance (urinary concentration) of creatinine. Why is creatinine clearance slightly higher than GFR?
Creatinine is secreted as well as filtered by the kidneys
Inhibitors of creatinine secretion will make serum concentration increase and will make GFR look worse, what are such inhibitors?
trimethoprim (antibiotic for bladder infections), cimetidine (H2 receptor agonist) ritonavir (AIDS med)
Albumin levels in kidneys are generally low, what are levels above 3mg/mmol indicative of?
leaky glomerulus and kidney damage
Where is the nephron does mass reabsorption (70% of Na), sugars, amino acids, bicarbonate occur?
Proximal tubules
All active transport (metabolically active area- vulnerable to ischaemic injury).
What is the role of the loop of Henle?
concentrates urine. Reabsorbs water in descending limb. Reabsorbs Na in ascending limb (25%)
Where do thiazide diuretics act?
Where do loop diuretics act?
Distal tubule
Loop diuretics
Aldosterone secretion is stimulated by angiotensin 2, Where is aldosterone produced?
Adrenal gland (zona glomerulosa)
How does aldosterone act?
Acts on the collecting duct, increases Na reabsorption via ENac channels(2%), increased K and H+ secretion indirectly.
Vasopressin, produced by the posterior pituitary gland, acts on the collecting duct, what does it do?
Increases expression of aquaporin 2–> increases water re-uptake
What medications can causes hypokalaemia?
Loop diuretics, Thiazide
Hyperkalaemia increases risk of heart attack. What medications can cause Hyperkalaemia
Spironolactone (aldosterone agonist), amiloride, ARBs, ACE inhibitors, Trimethoprim, Calcineurin inhibitors.
