A 60-year-old patient, known case of Hypertension for the past 25-year underwent renal artery Doppler which showed narrowing and turbulence in right renal artery. If the diameter of lumen is reduced by 50%, how much blood flow will be reduced?

Ans. (c) 1/16th(Ref: Ganong, 25th ed/p.573)Poiseuille-Hagen formula is:F=(PA -PB )*pr4/8eLSo, according to the above formula, blood flow is directly proportional to the fourth power of radiusSo, if the radius is halved, then blood flow decreases by 2 to the power 4 times which is 16 times