Imaging of kidny i htn by dr.abd alla shady md22

1. By
Abdalla Abdelhamid Shady, MD
Radiology Department
Urology and Nephrology Center
Mansoura University

2.  Hypertension is a common condition, affecting
about 20% of adults.
 Secondary hypertension accounts for only 5%-
20%
 of all cases of hypertension.
Causes of Secondary hypertension :
 Kidney disease.
 Tumours or other diseases of the adrenal gland.
 Coarctation of the aorta .
 Pregnancy.
 Use of birth control pills.
 Alcohol addiction.
 Thyroid dysfunction.

3.  Renovascular hypertension is the most common type
of secondary hypertension and is estimated to have a
prevalence between 0.5% and 5% of the general
hypertensive population.
 The term renovascular hypertension (RVH) refers to the
causal relationship between a (RAS) and its clinical
consequences, namely, hypertension or renal failure.
 Renal artery stenosis: narrowing or complete occlusion
of one or both renal arteries, defined by imaging at:
greater than 60% stenosis by Doppler or grater than
50% by angiography.

4. Causes of renal artery stenosis
Common etiologies
 Atherosclerotic disease (90%)
 Fibromuscular dysplasia (10%).
Less common etiologies
 Vasculitis
 Embolic disease.
 Dissection.
 Post-traumatic occlusion.
 Extrinsic compression of a
renal artery or of a kidney.

5. Classification of renal artery
stenosis:
 Unilateral.
 Unilateral in a single
functional kidney.
 Bilateral.
 Proximal.
 Distal.
 Moderate stenosis ( 50%-75%
of RA diameter)
 Sever stenosis( 75%)
 Total occlusion.
SeverityAnatomical :

6. Pathophysiolo
gy
 RAS ( 50%) under perfusion of the kidney
activation (renin - angiotensin system).
angiotensinogen angiotensin I.
angiotensin I angiotensin II.
 Angiotensin II, a potent vasopressor responsible for the
vasoconstrictive element of renovascular hypertension.
 Angiotensin II increases adrenal gland production of
aldosterone with subsequent retention of sodium and
water

7. Clinical Findings associated with renovascular
hypertension
 Refractory hypertension.
 Severe hypertension (diastolic blood pressure >120
mm Hg)
 Hypertension associated with progressive renal
impairment.
 Onset of hypertension before age 30 year.
 Abrupt onset of hypertension.
 Generalized atherosclerosis.
 Abdominal bruit.

13. Overview of Imaging Modalities
 IVU
 Ultrasound (US).
 Computed tomography (CT).
 Magnetic resonance imaging (MRI).
 Renal scintigraphy.
 Renal angiography

14. IVU
• The affected kidney small and smooth.
• The reduced perfusion on the affected side
produces a late nephrogram giving rise to a
hyperdense nephrogram.
• Notching of the ueretr due to compensatory
hypertrophy of the ureteric artery.

15. Ultrasound
• First step in the investigation.
• It is a simple non –invasive.
• Obvious size disparity between the two kidneys (2cm)
one kidney is abnormally small - slo unilateral RAS.
• Exclude an obvious structural abnormality coexistent
condition that may relate to the hypertension ( renal
scarring and rarely renal or adrenal tumours.

17. Normal renal Doppler waveform
• Rapid systolic rise.
• High-velocity diastolic flow.
• Small spike at the end of the systolic rise

18. Normal renal Doppler waveform :
 The PSV in the main renal artery less than 120 cm/sec.
 Acceleration time is the time from the start of systole to peak systole.
 A normal acceleration time for the main renal artery is less than 70 msec

19.  RI = PSV - EDV ∕ PSV .
 The values of RI in the main RA are higher in the hilar
region ( 50 : 80) than in the more distal small arteries.

20. Doppler criteria of RAS:
Direct criteria (proximal criteria ):
 Main renal artery.
 Site of the stenosis.
Indirect criteria (distal criteria ):
 Intrarenal arteries

21. Direct US signs ( Proximal criteria):
1. Doppler US artifacts caused
by poststenotic turbulence
(aliasing).
2. Renal artery PSV > 180
cm/sec.
3. Renal artery PSV–to–
abdominal aorta PSV ratio >
3.5.
4. Lack of Doppler US signal in
cases of occlusion. Mosaic flow is seen within the stenotic
area spectral Doppler waveform of the
stenotic area in the right RA. Increased
peak systolic velocities are seen (PSV 286
cm/s);

22. Indirect US signs ( Distal criteria):
Loss of early systolic peak.
AT > 70 ms.
A difference between the kidneys RI
more than 5%.
Pulsus parvus et tardus
(blunted and delayed
systolic upstroke).

23. Direct and indirect US findings in a patient with secondary hypertension due to RAS.
(a) elevated PSV (>200 cm/sec.
(b) Sagittal US image shows a pulsus parvus et tardus waveform distal to the site of stenosis, where there is blunting of the
systolic peak with a delayed upstroke. This waveform is quantified on the basis of an acceleration time longer than 70 msc.

24. Magnetic Resonance Angiography
 MRA is a non-invasive test for assessing RAS and has been widely
applied for clinical practice.
 Contrast-enhanced MRA forms the backbone of MRI of renal arteries, but
noncontract MRA with spechial techniques has also been used for
evaluating the renal arteries.
 Functional information can be added by measuring renal flow with cine
phase-contrast imaging. Diffusion and perfusion imaging can also be used
to measure renal ischemia. Another MR technique currently being
investigated, MRI BOLD , is able to assess renal oxygenation, which may
allow for functional assessment in patients with RAS .

25. Severe bilateral RAS (a) Coronal MIP image from MRA shows severe bilateral renal stenosis (arrows), which appear as
short occlusions. (b) Coronal source MR image shows left renal atrophy, suggesting that the left-sided stenosis is more
severe. A large renal cyst is also seen.

26.  Exposure to gadolinium contrast agents in patients
with renal failure and those maintained on dialysis
has recently been linked with the development of
nephrogenic systemic fibrosis a debilitating and
sometimes fatal disease affecting the skin, muscle,
and internal organs.

27. The main limitations of MR angiography
are
Evaluation of branch vessels.
The presence of a metallic stent.
Detection of accessory arteries.

28. CTA
 Contrast-enhanced CTA provides accurate anatomic images
of the renal arteries that enable the reconstruction of high-
resolution images in any plane.
 Advantages compared with arteriography include less
invasiveness, faster acquisitions, and multiplanar imaging.
 The disadvantages of this technique are its ionizing radiation
and its use of nephrotoxic contrast material.
 Normal results from CTA virtually rule out RAS.

29. Atherosclerotic RAS in an 82-year-old man with hypertension. CR image (a) and coronal MIP (b) images from a
CT angiogram show a focal severe short segment of narrowing (arrow) of the proximal renal artery. Additional
atherosclerotic changes and a fusiform aneurysm are present in the infrarenal abdominal aorta (* in b).
 In addition to directly visualized luminal narrowing, it also
show the secondary signs include poststenotic dilatation,
renal atrophy, and decreased cortical enhancement.

30. Coronal MIP CT A shows the presence of multiple alternating areas of narrowing and dilatation (arrow) of the right
renal artery. a “string of pearls” appearance (arrow) of the right main renal artery. This appearance is consistent with
FMD.

31. Renal Arteriography
 Intra-arterial digital subtraction angiography
(IADSA) is considered the reference standard for
demonstrating RAS and is an integral part of
angioplasty and stenting procedures.
 Angiography has high spatial resolution for
evaluating the main renal arteries as well as the
branch renal arteries.

38. ACE Inhibitor
Scintigraphy
Captopril renography is a functional assessment of renal perfusion.
In patients with unilateral RAS, a unilateral change in renal function
induced by ACE inhibition can be revealed with scintigraphy.
In these patients, ACE inhibitor scintigraphy induces significant
changes in the time-activity curves of the affected kidney in
comparison with baseline scintigraphy..

39. When using Tc 99m MAG3,a renogram curve showing:
• Diminished uptake.
• Flattened peak .
In sever cases the excretion may be also shows that the
curve continues rising through the period of observation

40. Renovascular disease in a 60-year-old
patient. (a) Baseline scintigram obtained
with Tc-99m MAG3 shows mild and
nonspecific abnormalities, with
decreased amplitude and delayed
peaking of the left renal curve
(arrowhead) relative to the right renal
curve (solid arrow).
(b) Scintigram obtained after
administration of captopril shows
diminished uptake in the left kidney, with
an abnormal curve (solid arrow)
suggesting left-sided renovascular
disease. The

41. Stenotic accessory right renal artery
Baseline Tc-99m DTPA scintigrams Captopril scintigrams

42. Limitation of captopril scintigraphy
 Bilateral RAS.
 Impaired renal function.
 Urinary obstruction .
 Chronic intake of ACE inhibitors.

43. Renal insufficiency
Baseline Tc-99m DTPA scintigrams Captopril scintigrams

44. Interventional radiology in the treatment of RAS
Percutaneous transluminal renal angioplasty alone
or in commination with stent implantation.
Selecting patients for renal revascularization:
• Refractory hypertension.
• Progressive azotemia.
• Recurrent pulmonary oedema.
• Bilateral renal artery stenosis
• Stenosis of renal artery supplying single functioning
kidney.

48.  US can be utilized regardless of level of renal
function.
 CTA and MRA are both effective modalities for
diagnosis of RAS, though both have been associated
with potential morbidity in the setting of impaired renal
function nephrogenic systemic fibrosis (NSF) in the
case of MRI and contrast material–induced
nephropathy (CIN) in the case of CT .
 Unenhanced CT does not provide useful diagnostic
information regarding RAS.
 Non-contrast MRI protocols are an alternative in
patients with impaired renal function.

49.  Renal scintigraphy also can be utilized for
functional assessement of RAS but has
decreased accuracy in patients with bilateral
RAS or impaired renal function.

50. Thank
You