<prompt> A 60-year old patient underwent renal aery doppler which shows narrowing and turbulence in right renal aery. If radius of the aery is reduced by 13rd, resistance to blood flow in right kidney would have increased by:3 times9 times16 times81 times  <response>: Fouh power law of radius Blood flow varies directly and resistance inversely with the fouh power of the radius r 4. If the radius is changed by a factor of 3 reduced by 13rd, resistance would change by 34. 