Renal Vascular Disease

Question 1

What is the link between HTN and renal disease?

Answer 1

HTN causes renal disease, and renal disease often causes HTN

Question 2

What are the typical and rarer causes of renovascular disease?

Answer 2

Typical:

• Atherosclerosis - in 80% if these they are >50yrs, arteriopaths often with co-existant, IHD, stroke, PVD)
• Fibromuscular dysplasia - around 10%. tend to be younger women

Rarer:
- Takayasu’s arteritis, anti-phospholipid syndrome, post renal transplant, thromboembolism, external compression.

Question 3

What are the signs of renovascular disease?

Answer 3

• Increased BP resistant to treatment
• worsening renal function after ACE-i or ARB in bilateral renal artery stenosis.
• ‘Flash’ pulmonary oedema (sudden, no LV impairment)
• Abdominal +/- carotid or femoral bruits may be found, weak leg pulses

Question 4

What tests would you do for suspected renovascular disease?

Answer 4

• USS - asymmetry of size (affected smaller) + disturbance of renal blood flow on doppler
• CT/MR angiography more sensitive
• renal angiography is ‘gold-standard’ but invasive so do after CT/MR

Question 5

How do you treat renovascular disease?

Answer 5

• Comprehensive antihypertensive regimes

- Transluminal angioplasty +/- stent or renovascular surgery

Question 6

What is HUS? What are its common features?

Answer 6

Haemolytic uraemic syndrome - characterised by Microangiopathic Haemolytic Anaemia (MAHA, a process of intravascular haemolysis + red cell fragmentation)

• Endothelial damage triggers thrombosis, platelet consumption and fibrin strand deposition i the renal microvasculature
• The strands cause mechanical destruction of passing red cells.
• Thrombocytopenia and AKI results

Question 7

What causes HUS?

Answer 7

• 90% from E. Coli strain O157
• produces a toxin that attacks endothelial cells.
• outbreaks tend to occur in children, undercooked meat

Question 8

What are the signs of HUS?

Answer 8

• Abdominal pain
• Bloody diarrhoea
• AKI

Question 9

What tests do you carry out for suspected HUS?

Answer 9

• Check urine for blood + protein
• Blood film - fragmented blood cells
• Low platelets and Hb

Question 10

How do you treat HUS?

Answer 10

• Seek help,
• Dialysis for AKI might be needed
• Plasma exchange used in sever persistent disease

Question 11

What is TTP? What are its common features?

Answer 11

Thrombotic Thrombocytopenic Purpura - overlaps with HUS

• Many clinicians consider them a spectrum of disease
• MAHA present, with jaundice and low platelets
• Can also include AKI, fluctuating CNS signs and fever.

Question 12

What causes TTP?

Answer 12

• Genetic susceptibility - deficiency of a protease that normally cleaves multimers of Von Wilebrand Factor.
• Large VWF multimers form, causing platelt aggregation and fibrin deposition in smal vessels, leading to micro thrombi.
• 40% idiopathic
• autoimmunity (SLE)
• cancer
• pregnancy
• drug associated

Question 13

Is TTP serious? How do you test for it?

Answer 13

HAEMATOLOGICAL EMERGENCY

Test as in HUS.

Question 14

How do yo treat TTP?

Answer 14

• Plasma exchange may be life-saving
• Non-responders try steroids

Is a rare disease, but treatment needs to be prompt so diagnosis must be made early.
If thrombocytopenia and anaemia due to unexplained causes, think TTP and refer immediately.
Urgent peripheral blood smear should show MAHA.

Question 15

What is important to remember with diabetes and renal vascular disease.

Answer 15

Diabetes should really be thought of as a vascular disease.
Both type 1 + 2 can lead to renal vascular disease (2 more than 1)

!! SCREEN DIABETICS EVERY YEAR FOR MICROALBUMINAEMIA !!

Microalbuminaemia - 30-300mg albumin/24hr.
Gives an early warning sign of impending renal problems. Also a strong independent risk factor for cardiovascular disease.
- STANDARD DIPSTICKS DO NOT DETECT THIS, so use special ones or use albumin: creatinine ratio ( >2.5 men, >3.5 women)

Question 16

What happens if you find a diabetic that test positive for microalbuminaemia?

Answer 16

• Start on ACE-i or ARB regardless of BP. These reduce intraglomerular pressure and so proteinuria.
• Controversial evidence to support the use of these drugs
• Target BP in diabetics with no proteinuria 130/80,
  if microalbuminaemia / proteinuria 125/75

Question 17

Is microalbuminaemia reversible?

Answer 17

Yes, if caught early and tightly managed
- tight glycaemia control
- tight BP control
- Manage CV risk
(essentially all diabetic management steps)

Question 18

What are the risks for cholesterol emboli?

Answer 18

• Atheroma
• Increased cholesterol
• aortic aneurysm
• thrombolysis
• arterial catheterisation

Question 19

What are the signs and treatment of renal artery cholesterol emboli?

Answer 19

Signs - fever, uncontrolled BP, livedo reticularis, oliguria, AKI, gangrene, GI bleeds

Treatment - haemodynamic monitoring and dialysis
statins, avoid anticoagulants