GFR - Glomerular Filtration Rate

• Adult Male 125ml a min

  • The avg filtration rate from males (this number was take from a healthy army personel

• Adult women

  • Lower rates of filtration

• Increase GFR

• Decrease GFR

• Why would it increase

• Why would it decrease

• In some instances people have lost 2/3 of GFR before symptoms occur

90% renal function when lost (you cannot get on the transplant list until this occurs

Rationale of GFR tests

• The substance must be small enough to pass through the glomerular filter

• Measure the concentration of this substance in the plasma (p)

• The maesurement of the concentration of urine (u)

• The measurement of urine flow per minute (v)

• P X GFR = U X V

• Substances used

  • Inulin (most acurate)

  • Creatinine - most common one used

  • Urea

Testing tubular reabsorption

• The counter current multiplier - this is what controls osmolality

• Water can go to or from the vascular tree depending on the pressure gradient itself

• The medullary portion is harder to get urine

• If the counter current multiplier was to be interfered with the urine will hold more water showing signs of diuresis

When Fasting you must not have and fluids the night before (15 hour fast)

Collect it three times

With the fast, we will become even better a filtering

Isothenurea - a kidney that is not keeping up and responding to the drive of the body

It could be insufficient ADH production.

• Patient is unable to concentrate urine in the presence of clinical dehydration.

• Could be many reason for this

Value of Test

• A copius GFR

• A proper amount and distribution of renal blood flow

• Healthy tubular cells

***Assessments of the Kidney's concentration-dilution functions provide the most sensitive (most incidence of true positive) means of detecting early or mild impairment of renal physiology. A patient with completely normal concentrating ability is unlikely to have a serious kidney malfunction

Mess around with the electrolytes

Possible causes of loss of concentrating ability when needed

• Hypokalemia

• Hypercalcemia

• Absence of ADH

• Diminished GFR

• Amyloidosis

• Increased solute load

• Loop diuretics

• Atherosclerotic disease

Metabolic Acidosis in Chronic Renal Failure

• Whole nephrons are destroyed (parallel glomerular and tubular failure)

• The remaining nephrons are largely functionally intact and produce a very acid urine

• The disproportion between total acid output and acid load secondary to diminished tubular mass results in retention and the typical metabolic acidosis of chronic renal failure.

Category: Medicine Notes