Renal Flashcards
Why is the left kidney taken during donor transplantation?
Because it has a longer renal vein
Path of renal blood flow, beginning with the renal artery?
Renal artery -> segmental artery -> interlobar artery -> arcuate artery -> interlobular artery -> afferent arteriole -> glomerulus -> efferent arteriole -> vasa recta/peritubular capillaries -> enous outflow
Explain the fluid compartments of the body.
- Total body water (TBW - 60% of body mass) + non water mass (NWM - 40% of body mass) = Body mass
- Total body water = Intracellular fluid (ICF - 2/3 TBW) + Extracellular fluid (ECF - 1/3 TBW)
What is the 60-40-20 rule?
% of body weight for average person:
60% total body water
40% ICF
20% ECF
What are the components of ECF?
Interstitial fluid (75% ECF) Plasma (25% ECF)
How can plasma volume be measured?
Radiolabeling albumin
How can ECF volume be measured?
With inulin or mannitol
What is normal osmolality?
285-295 mOsm/kg H2O
What are the components of the glomerular filtration barrier?
- Fenestrated capillary endothelium
- BM with type IV collagen chains and heparan sulfate
- Epithelial layer consisting of podocyte foot processes
How does the glomerular filtration barrier select for filtration?
Charge and size
What creates the charge barrier?
All three layers of the barrier contain negatively charged glycoproteins, preventing negatively charged molecule entry (eg, albumin)
What creates the seize barrier?
Fenestrated capillary endothelium prevents entry of >100 nm molecules/blood cells
Podocyte foot processes interpose with BM -> slit diaphragm (prevents entry of molecules >50-60 nm)
Renal clearance of a substance = ?
[(Urine concentration of X)(Urine flow rate)]/Plasma concentration of X
What is renal clearance?
The volume of plasma from which the substance is completely cleared per unit time (mL/min)
What is happening if clearance does not equal GFR?
If clearance is greater than GFR, net tubular secretion
If clearance is less than GFR, net tubular reabsorption
What can be used to calculate GFR? Why?
Inulin clearance; it is freely filtered and neither reabsorbed nor secreted
GFR = ?
UV/P (of inulin)
Normal GFR = ?
~100 mL/min
What is an approximate measure of GFR? Why is it a slight overestimate?
Creatinine clearance; slightly overestimates GFR because creatinine is moderately secreted by renal tubules
What is used to estimate effective renal plasma flow (eRPF)?
Para-aminohippuric acid (PAH) clearance; between filtration and secretion via the proximal tubule, there is nearly 100% excretion of all PAH that enters the kidney (slight underestimate of the true RPF)
eRPF = ?
UV/P (of PAH)
Renal blood flow (RBF) = ?
RPF/(1 - Hct)
FF = ?
GFR/RPF
Normal FF?
20%