12. Vascular disorders of the kidney

Question 1

What are the disease affecting the renal arteries?

Answer 1

• Renal artery stenosis
• Cholesterol embolism
• Vasculitis

Question 2

What is renal artery stenosis and its causes?

Answer 2

It is a renovascular disease defined as stenosis of the renal artery or one of its branches

Causes:

• Atherosclerosis (65%, usually elderly with comorbidities)
• Fibromuscular dysplasia (35%, < 55-years-old)
• Rare cases:
  
  • Takayasu arteritis
  • Antiphospholipid syndrome
  • Post-renal transplant
  • Thromboembolism
  • External compression

Question 3

What are the hemodynamic consequences of renal artery stenosis?

Answer 3

• Decreased RBF ==> decreased GFR
  
  • This activates compensatory mechanisms of RAAS ==> systemic hypertension

Question 4

What are the signs of renal artery stenosis?

Answer 4

• Rapid onset hypertension, resistant to treatment
• Worsening of renal function after ACEI/ARB in bilateral renal artery stenosis
• Pulmonary edema of unknown etiology
• Abdominal and/or carotid or femoral bruits with weak leg pulse

Question 5

What are the diagnostic tests of renal artery stenosis?

Answer 5

• US: renal size asymmetry (affected side is smaller), disturbances in renal blood flow on doppler US
• Dynamic renal isotope scan
• CT/MR angiography (more sensitive)
• Renal angiography

Question 6

What is the treatment of renal artery stenosis?

Answer 6

• Objective is to decrease the BP, prevent further loss of renal function and prevent cardiovascular events
  
  • Comprehensive antihypertensive therapy
    
    • ACEI, Calcium channel blockers, diuretics, statins, aspirin
  • Transluminal angioplasty and stent placement
  • Revascularization surgery (rare)

Question 7

From where do cholesterol embolisms arise from?

Answer 7

• May be released from atheromatous plaques (often aorta) –> lodges in microcirculation (renal vessels, peripheral circulation, gut) ==> ischemia!
  
  • An inflammatory response may lead to fever, myalgia and eosinophil accumulation
• It is usually the result of endovascular procedures (arterial catheterization)
  
  • Either immediatly of 1-3 days after the procedure

Question 8

What are the are the signs of cholesterol embolism?

Answer 8

Multisystemic disease:

• Fever
• Uncontrolled BP
• Livedo reticularis
• Oliguria and AKI
• Gangrene
• GI bleeds, ischemia and necrosis

The condition is often progressive and fatal, however, some patients regain renal function after dialysis.

Question 9

What are vasculitides?

Answer 9

• They are inflammatory disorders of the blood vessel walls ==> destruction (aneurysm/rupture) or stenosis
• It may be a primary conditions or secondary due to autoimmune disorders, infections or malignant diseases
• Affects vessels of any organ and the presentation depends on the organ affected
• Different types prefferentially affect different organs, causing different patterns of symptoms
  
  • But, the presentation may often only be of overwhelming fatigue with high ESR/CRP.
• Suspected in any patient presenting with multisystemic disease, which can’t be explained by an infectious process.
  
  • If presentation doesn’t fit clinically or serologically into a specific category –> Consider malignancy-associated vasculitis
• A severe vasculitis flare-up is a medical emergency!!!

Question 10

What is the affected organ presentation of vasculitis?

Answer 10

Question 11

What is the classification of vasculitis?

Answer 11

Question 12

How do we diagnose different vasculitides and how do we manage them?

Answer 12

• Lab tests can help in the diagnosis:
  
  • ESR/CRP
  • ANCA
  • Creatinine
  • Urinalysis (proteinuria, hematuria, casts)
  • Biopsy (required!)

Management:

• Steroids (large vessel vasculitis)
• Combination of steroids + IV cyclophosphamide (medium/small-vessel vasculitis)

Question 13

What is Giant cell (temporal) arteritis?

Answer 13

• Granulomatous inflammation of the aorta and major branches (often superficial temporal artery) in patients > 50-years-old
• Typically 2-year course and then complete remission

Symptoms:

• Headache
• Temporal artery and scalp tenderness
• Jaw claudication
• Sudden blindess (one eye typically)

Question 14

What is Takayasu’s arteritis?

Answer 14

• Affects more femaly < 50-years-old
• Similar to Giant cell arteritis
  
  • Affect aorta and major branches
• Pulseless disease

Question 15

What is polyarteritis nodosa (PAN)?

Answer 15

• It is a necrotizing vasculitis causing aneurysms and thrombosis in medium-sized arteries ==> infarction of an organ with severe systemic symptoms

​Symptoms:

• Constitutional symptoms
• It affects all organs except the lung
  
  • Skin rask and punched-out ulcers
  • Renal
  • Cardiac
  • GIT
  • GUT

Question 16

What is kawazaki arteritis?

Answer 16

• It is a childhood variant of PAN affecting mostly asian populations
• It affects the coronary arteries and causes lymph node enlargements

Question 17

What is Henoch-Schönlein purpura?

Answer 17

• Small-vessel vasculitis with dominant IgA immune complex deposits, which affect:
  
  • Skin
  • GIT
  • Glomeruli (nephritic syndrome or isolated hematuria)
  • Joint

Question 18

What is Wegener’s granulomatosis?

Answer 18

• ≥ 40 years old
• Necrotizing, granulomatous inflammation of the upper and lower respiratory organs
• Necrotizing thrombogenic vasculitis of isolated glomeruli: glomerulonephritis
• Necrotizing pneumonitis, chronic sinusitis, nasopharyngeal ulcerations, renal damage
• Serum C-ANCA ­ (cytoplasmic anti-neutrophil cytoplasmic antibodies)

Question 19

What is cryoglobulinemia?

Answer 19

• MPGN (nephritic syndrome) may be see in type II cryoglobulinemia
• The blood contains large amounts of cryoglobulins – proteins (mostly immunoglobulins themselves) that become insoluble at reduced temperatures.

Question 20

What are the ANCA positive GN-producing vasculitides?

Answer 20

Question 21

Which are the diseases affecting renal capillaries?

Answer 21

• Hypertensive nephrosclerosis
• Thrombotic microangiopathies (TMA)
  
  • Hemolytic uremic syndrome (HUS)
  • Thrombotic thrombocytopenic purpura (TTP)

Question 22

What is hypertensive nephrosclerosis?

Answer 22

• Long-standing benign hypertension leads to slow and progressive loss of renal function
• Histology demonstrates:
  
  • Arteriolar thickening and hyalinization
  • Glomerulosclerosis
  • Interstitial inflammation and fibrosis.
• Other organs are affected:
  
  • LVH
  • Retinal changes
  • Microalbuminuria

Question 23

What are thrombotic microangiopathies?

Answer 23

• A group of acute syndrome characterized by:
  
  • Microangiopathic hemolytic anemia (MAHA)
  • Thrombocytopenia
  • Possible, renal (AKI) and CNS abnormalities
• They share common pathophysiologies:
  
  • Inciting event triggers thrombosis, platelet consumption and fibrin strand deposition, mainly in renal vasculature
    
    • Leads to mechanical destruction of passing RBCs

Types:

• Hemolytic uremic syndrome (HUS)
• Thrombotic thrombocytopenic purpura (TTP)
• Transplant nephropathy
• Radiation nephropathy
• Scleroderma renal crisis
• Malignant HTN
• Antiphospholipid syndrome
• HELLP syndrome

Question 24

What is hemolytic uremic syndrome (HUS)?

Answer 24

• In 90% of cases, E. Coli strain O157 is the incinting event as it produces shiga toxins that attack endothelial cells
  
  • Atypical cases can be caused by complement component deficiencies
• It usually affects young children in outbreaks after eating undercooked contaminated meat

Symptoms:

• Abdominal pain
• Bloody diarrhea
• AKI (hematuria/proteinuria)

Diagnosis:

• Blood film shows
  
  • Fragmented RBCs (Schistocytes)
  • Decreased platelet count and Hb concentration

Management:

• Dialysis may be required in case of AKI
• Plasmapheresis is used if persistent disease

Prognosis:

• Worse in non-E. Coli cases
• Mortality is 3-5%, good prognosis if caught early

Question 25

What is thrombotic thrombocytopenic purpura (TTP)?

Answer 25

• Genetic or acquired deficiency of ADAMTS13, which normally cleaves multimers of VWF
  
  • Idiopathic (40%)
  • Autoimmunity (e.g. SLE)
  • Cancer
  • Pregnancy
  • Drug-associated (e.g. quinine)
  • Bloody diarrhea prodrome
  • Hematopoietic stem cell transplant
• The uncleaved VWF multimers can cause platelet aggregation and fibrin deposition in small vessels ==> microthrombi

Clinical features:

• MAHA (with jaundice)
• Low platelet
• Sometimes, AKI, fluctuating CNS signs (seizures, hemiparesis, consciousness, vision)
• Fever

Treatment:

• It is a hemolytic emergency and urgent plasma exchange may be life-saving
• Steroids are used in non-respondes
• New therapies: eculizumab (target terminal complement pathway C5), rituximab

Question 26

What is the disease affecting renal veins?

Answer 26

Renal vein thrombosis (RVT)

Question 27

What is renal vein thrombosis (RVT)?

Answer 27

• It is usually an asymptomatic condition and happens in the setting of nephrotic syndrome or malignancy
  
  • It may worsen proteinuria and renal function

Etiology:

• Acute RVT may result from:
  
  • Trauma
  • Dehydration
  • Hypercoagulable state

Symptoms:

• Flank pain
• Hematuria
• Increased serum LDH
• Proteinuria
• Renal failure (if bilateral)

Diagnosis:

• US, MRI, CT, Venography

Treatment:

• LMWH + anticoagulation therapy for 6-12 months
• Catheter thrombectomy if acute RVT
• Prophylactic anticoagulation is recommended for high risk patients (low albumin, heavy proteinuria)