Renal artery stenosis

Renal artery stenosis (RAS) refers to a narrowing of a renal artery. When the process occurs slowly, it leads to secondary hypertension. Acute renal artery stenosis does not lead to hypersecretion of renin.

Pathology

When the stenosis occurs slowly, collateral vessels form and supply the kidney. The kidney wrongly senses the reduced flow as low blood pressure (via the juxtaglomerular apparatus) and releases a large amount of renin that converts angiotensinogen to angiotensin I. Angiotensin I is then converted to angiotensin II with the help of angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II is responsible for vasoconstriction and release of aldosterone which causes sodium and water retention, thus resulting in secondary hypertension.

Renal artery stenosis may be caused by several pathological processes:

Occurrence is not uncommon following a renal transplant.

Radiographic features

Ultrasound

Ultrasound, although most freely available, cheap and often used first line, is relatively operator-dependent and may prove time-consuming.

CT angiography

The three-dimensional reconstruction of the renal vascular tree provides a reliable method of visualizing the entire vascular tree. Images are acquired with thin collimation and bolus tracking on the abdominal aorta. Sensitivity and specificity varying between 90 to 99% have been reported 7.  Both the raw data and 3D reconstructions should be viewed. Additionally, supernumerary arteries may be identified.

MR angiography

Different imaging methods can be used:

  • time of flight (TOF): whereby the high velocity of the blood jet at the level of stenosis appears as a loss of signal (black)
  • phase contrast technique
  • contrast-enhanced MRA: gadolinium is used as a contrast agent

Three-dimensional reconstruction technique offers sensitivity and specificity values around 90 to 100% 7. In some cases, renal impairment does not permit the use of contrast, in which case TOF imaging is beneficial.

Nuclear medicine
ACE inhibitor scintigraphy
  • the affected kidney with renovascular hypertension shows impaired function due to ACE inhibition; based on this principle scintigraphy has been very much useful for diagnosis of renal artery stenosis
  • performed by IV administration of enalapril maleate after 15 minutes
  • sequential images and scintigraphic curves are plotted for the renal cortex and pelvis; renal uptake is measured for every 1-2 min interval after administering the IV injection
  • typical isotopes used are Tc-99m MAG3, Tc-99m DTPA or I-123 0-iodohippurate 6
  • interpreted as either low, intermediate or high probability
Share article

Article information

rID: 3871
Section: Gamuts, Approach
Synonyms or Alternate Spellings:
  • Renal artery stenosis: differential diagnosis
  • Renal arterial stenosis
  • Renal artery stenosis (RAS)
  • Renal artery stenoses
  • Renal arterial stenoses

Support Radiopaedia and see fewer ads

Cases and figures

  • Case 1: with delayed nephrogam
    Drag here to reorder.
  • CE-MRA of the ren...
    Case 2: CE-MRA
    Drag here to reorder.
  • Case 3: on CT
    Drag here to reorder.
  • Case 3: angiography
    Drag here to reorder.
  • Case 4
    Drag here to reorder.
  •  Case 5
    Drag here to reorder.
  • Case 6: on right with post-stenotic dilatation
    Drag here to reorder.
  • Case 6: with parvus-tardus waveform
    Drag here to reorder.
  • Case 7
    Drag here to reorder.
  • Case 8: post stenting
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.