Editing Renal Hypertension (section)

==== Imaging ====

* '''Screening Tests'''
** '''The screening tests that provide the highest sensitivity and specificity are (3):'''
**# '''Magnetic resonance angiography (MRA)'''
**# '''Computed tomography angiography (CTA)'''
**# '''Duplex Doppler US'''
*** '''Renal scintigraphy is no longer recommended as a screening test to establish the diagnosis of RAS.'''
*** '''CTA and MRA do not visualize the distal renal arterial tree well'''
*** A transient deterioration of renal function is not infrequently seen following a contrast load in patients with significant RAS and limited renal function
** '''MRA with Gadolinium'''
*** '''May be used as a highly sensitive and specific non-invasive test to assess the functional significance of a renal vascular lesion; both the RBF and the GFR can be determined by the study digital subtraction angiography (DSA)'''
*** '''Concerns regarding the possibility of gadolinium-induced nephrogenic systemic fibrosis have diminished its utility in those with unstable or reduced renal function (GFR <30 mL/min).''' In these patients, a non-contrast MRA study may be performed, but this shows far less sensitivity and positive predictive value than a gadolinium-enhanced study
** '''CTA'''
*** Limited in those with renal insufficiency because both the sensitivity and specificity declines in the presence of renal insufficiency (serum creatinine >1.7 mg/dL), and the risk of dye-induced nephrotoxicity increases
** '''Duplex Doppler US'''
*** '''The most important indicator of renal artery stenosis is increased peak systolic velocity (PSV > 180cm/sec)'''
*** Similar to MRA, duplex Doppler US provides both anatomic and functional information.
*** Disadvantages:
**** Time-consuming
**** Highly operator dependent
**** Technically difficult test to perform
*** The sensitivity of this technique may be further increased when ACE inhibition is used  

* '''Confirmatory test'''
** '''Angiography'''
*** '''Despite a negative screening test, renovascular disease may still be present, particularly if the lesion is in the distal or intrarenal portion of the artery.'''
*** '''Both conventional renal angiography and intra-arterial digital subtraction angiography remain the gold standard for diagnosing renovascular disease and are indicated if the clinical index of suspicion is high and intervention is contemplated, regardless of the outcome of the screening tests'''