Renal damage and ACE inhibitor use in renal artery stenosis

The glomerular filtration pressure is determined by three main variables:

• systemic blood pressure
• vasomotor tone in the afferent arteriole
• vasomotor tone in the efferent arteriole

In cases of bilateral renal artery stenosis (or unilateral stenosis if there is only one functional kidney):

• the glomerular filtration pressure is dependent on the vasoconstriction of the efferent arteriole because the resistance of the afferent blood vessels has been pathologically increased
  • vasoconstriction of the efferent arteriole is mediated by angiotensin II
  • administration of an ACE inhibitor abolishes the vasoconstriction of the efferent arteriole resulting in an abrupt fall in the glomerular filtration rate
  • the deterioration in renal function due to ACE inhibitors is usually reversible on stopping the drug

The EMC states that a contraindication to use of an ACE inhibitor is

• significant bilateral renal artery stenosis or renal artery stenosis in a single functioning kidney (1)

Reference:

• electronic medicines compendium (emc). Ramipril 2.5mg tablets (Accessed 20/7/21)