Renal Artery Stenosis

Question 1

What are other names for Renal Artery Stenosis (RAS)?

Answer 1

Renovascular Hypertension (RVH) and Renal Artery Occlusion Disease (RAOD)

Question 2

What can Renal Artery Stenosis progress to?

Answer 2

Chronic Kidney Disease (CKD) which is -Ischemic Nephropathy

Question 3

What is the most common cause of RAS in the elderly?

Answer 3

Atherosclerosis (usually affects proximal renal artery)

Question 4

What are common causes of RAS in young population ?

Answer 4

Fibromuscular Dysplasia (affects mid to distal renal artery)

Question 5

Which condition is associated with RAS in young Indian/Asian population ?

Answer 5

Takayasu Arteritis (affects proximal renal artery)

Females are more affected and the ratio of females : males is 9 : 1

Question 6

Which condition is associated with RAS in young males and involves the entire renal artery?

Answer 6

Polyarteritis Nodosa

Question 7

What is the key pathological change in unilateral RAS?

Answer 7

Asymmetric kidney size

Question 8

Pathogenesis of unilateral RAS

Answer 8

Renal blood flow to one kidney is reduced due to renal artery stenosis which activates RAAS so aldosterone and angiotensin 2 levels increase

Angiotensin 2 being a potent vasoconstrictor increases the bp causing htn

In normal kidney blood flow increases which causes “pressure natriuresis” this reduces reabsorption from the normal kidney which causes loss of na+ and h20

Question 9

What is the screening test for RAS?

Answer 9

Renal Doppler (USG)

Question 10

What is the investigation of choice (IOC) for RAS?

Answer 10

CT Renal Angiography or MR Angiography

Question 11

USG finding in Unilateral RAS ?

Answer 11

Asymmetric kidneys

Question 12

What is the treatment for unilateral RAS-induced HTN?

Answer 12

ACE Inhibitors / ARBs

PTRA (Percutaneous Transluminal Renal Angioplasty)
PTRA is done only when kidney size is more than 8cm

Question 14

Pathogenesis of bilateral RAS

Answer 14

Earlier in unilateral RAS we saw there is pressure natriuresis in normal side but here there is no normal side so there is loss of pressure natriuresis which reduces RIHP

So there is increased na+ and h2o retention which causes Intravascular volume overload

This causes recurrent “flash pulmonary edema”

Question 15

DOC for B/L RAS

Answer 15

Diuretics

Question 16

True or false:

ACE inhibitors are DOC for B/L RAS

Answer 16

False

ACE Inhibitors are C/I in B/L RAS because they may cause Frank renal failure

Question 17

What is seen in fibromuscular dysplasia on imaging?

Answer 17

“String of beads” appearance on CT Renal Angiography

Question 18

What is the hallmark Doppler ultrasound finding in RAS?

Answer 18

Parvus Tardus Pattern

Question 19

What histological layer is involved in fibromuscular dysplasia?

Answer 19

Tunica media (medial fibroplasia)

Question 20

In fibromuscular dysplasia, what population is most commonly affected?

Answer 20

Young girls

Question 21

What percentage of fibromuscular dysplasia cases involve cerebral vessels?

Answer 21

25%

Question 22

What is the best treatment for fibromuscular dysplasia?

Answer 22

PTRA (Percutaneous Transluminal Renal Angioplasty)

Question 23

What are the Doppler criteria for diagnosing RAS?

Answer 23

1) RI (Resistivity Index) < 0.8

2) Peak systolic velocity > 180 cm/s

3) RAR (Renal/ Aortic Blood flow Ratio) > 3.5

4) delta RI (difference between Resistivity Index of both kidneys) >0.05

If this criteria satisfied then CT or MR angigraphy taken for investigation

If conformed then conventional angiography for stenting

Question 24

True or false:

Fibromuscualar dysplasia is inflammatory condition

Answer 24

False

FMD is non atherosclerotic non inflammatory arteriopathy