Free water clearance decreased by ?
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Free Water Clearance
- Free water clearance is the amount of water cleared from the plasma, resulting in urine or the excretion of water independent of solutes.
- Free water clearance or CH2O gives the knowledge of concentration and dilution of urine
- It is the difference between rate of urine flow and the clearance of osmoles (clearance of osmoles or Cosm is the amount of water necessary to excrete the osmotic load in a urine that is isotonic with plasma).
- Significance of Free Water Clearance
- Free water clearance can be used as an indicator of water regulation.
- A free water clearance of zero means the kidney is producing urine that is isotonic with respect to the plasma.
- Values greater than zero imply that the kidney is producing a dilute urine through the excretion of solute-free water.
- Values less than zero imply that the kidney is conserving water resulting in the production of concentrated urine.
- Hypertonic or hyperosmotic:
- Under conditions of dehydration and SIADH, the kidneys absorb more water, in consequence the urine becomes more concentrated ( -CH2O or negative free water clearance)
- Hypotonic or hyposmotic:
- During high intake of water and diabetes insipidus, the kidneys excrete more water, in consequence, the urine becomes more diluted (+CH2O or positive free water clearance)
- The production of a concentrated or dilute urine depends on circulating ADH.
- CH2O is often used to determine how well ADH is functioning in the kidney to regulate the composition of urine and plasma.
Some relevant screenshots from KDT, stating that Furosemide decreases (or more correctly said – blocks) both positive and negative Free water clearance :
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