Estimation of glomerular filtration rate

1. Renal function, in nephrology, is an indication
of the state of the kidney and its role in renal
physiology.

2. It is the volume of
fluid filtered from
the renal
Glomerular
capillaries into
the Bowman's
capsule per unit
time.

3.  It is calculated by
measuring any chemical
that has a steady level in
the blood, and is freely
filtered but neither
reabsorbed nor secreted
by the kidneys
 GFR is typically recorded
in units of volume per time.

7.  Serum creatinine level are used in
measuring GFR.
 is produced naturally by the body.
 It is freely filtered by the glomerulus.
 But it is actively secreted by the
peritubular capillaries in very small
amounts so creatinine clearance
overestimates actual GFR by 10-20%

8.  Problems with creatinine (varying muscle
mass, recent meat ingestion, etc.) have
led to evaluation of alternative agents for
estimation of GFR

9.  The GFR can be determined by injecting inulin into
the plasma.
 its rate of excretion is directly proportional to the
rate of filtration of water and solutes across the
Glomerular filter.
 In early stage renal disease, the inulin clearance
may remain normal due to hyper filtration in the
remaining nephrons
 Incomplete urine collection is an important source of
error in inulin clearance measurement.

10.  Protein secreted by most cells in the body that is
freely filtered at the glomerulus and not
reabsorbed equations have been developed
linking estimated GFR to serum cystatin C levels

11.  One method of determining GFR from creatinine is
to collect urine (usually for 24-hours) to determine
the amount of creatinine that was removed from
the blood over a given time interval.
 Creatinine clearance (CCr) is calculated from the
creatinine concentration in the collected urine
sample (UCr), urine flow rate (V), and the plasma
concentration (PCr).

13.  Example: A person has a plasma creatinine
concentration of 0.01 mg/ml and in 1 hour
produces 60ml of urine with a creatinine
concentration of 1.25 mg/mL.

16.  http://www.nlm.nih.gov/medlineplus/ency/article/00
7305.htm
 http://en.wikipedia.org/wiki/GFR