Question

If, during an infusion of para-aminohippuric acid, peripheral venous plasma PAH level is 0.02 mg/ml (not above renal threshold), ** PAH level is 16 mg/ml and ** flow rate 1 ml/min, then the

A. PAH level in renal venous blood must exceed 0.02 mg/ml.

B. PAH level in renal arterial blood must be about 0.02 mg/ml.

C. PAH level in glomerular filtrate must be about 0.02 mg/ml.

D. Renal plasma flow is nearer 800 than 1000 ml/minute.

E. Renal blood flow is nearer 1300 than 1500 ml/minute if the haematocrit is 0.40.

Answer 1

A. False The renal venous blood level would be negligible.

B. True Since PAH is excreted only by the kidneys, the PAH level in peripheral venous blood determines the level entering the arterial system, and hence the renal arteries.

C. True Since PAH is freely filtered.

D. True Flow = PAH clearance = UV/P = 161/0.02 = 800 ml/minute.

E. True Blood flow = plasma flow/0.6 = 1333 ml/minute.