Definition
- Glomerular filtration rate (GFR) is the volume of filtrate formed by the glomerular filtering membrane of both kidneys per unit time.
- Normal GFR is 125 ml/min (7.5 L/h or 180 L/day).
Determinants of GFR
Determinants of glomerular filtration rate
Determinant
Renal blood flow
- Relationship to GFR
- Directly related; renal vasodilation maintains GFR
Glomerular capillary hydrostatic pressure
- Relationship to GFR
- Directly related; raised by afferent dilation or efferent constriction
Capsular (Bowman's/tubular) hydrostatic pressure
- Relationship to GFR
- Inversely related, opposes filtration; raised by tubular obstruction
Plasma oncotic pressure
- Relationship to GFR
- Inversely related, opposes filtration; lowered in hypoproteinemia
Glomerular capillary permeability
- Relationship to GFR
- Directly related; increased in glomerulonephritis
Effective filtration surface area
- Relationship to GFR
- Directly related; widened by mesangial relaxation, narrowed by mesangial contraction