The effective renal plasma flow, which equals the clearance of PAH, is less than the true renal plasma flow because:
A. The fraction of PAH filtered is less than the filtration fractionB. The plasma entering the renal vein contains a small amount of PAH
C. The cortical and medullary collecting ducts are able to reabsorb some PAH
D. The calculated clearance of PAH depends on the urinary flow rate
The Answer is B.
The clearance of PAH equals the true
renal plasma flow only if the kidney reabsorbs all of the filtered PAH, that
is, no PAH appears in the renal vein. Because the kidney is only able to
reabsorb approximately 85 to 90% of the filtered PAH, some PAH appears in the
renal vein, and the PAH clearance is less than the true renal plasma flow.
