Vascular diseases of kidneys

Question 1

What are the 3 types of large vessel disease?

Answer 1

1. ACUTE RENAL ARTERY OCCLUSION/INFARCT
2. RENAL ARTERY STENOSIS/ISCHAEMIA
3. RENAL VEIN THROMBOSIS

Question 2

Why is it important to detect acute renal artery occlusion/infarct?

Answer 2

• important, potentially reversible cause of renal failure

Question 3

Causes of acute renal artery occlusion/infarct

Answer 3

• abdominal trauma, surgery, embolism, vasculitis, extra-renal compression, hypercoagulable state, aortic dissection
• kidney transplant more vulnerable

Question 4

Px of acute renal artery occlusion/infarct

Answer 4

(depend on presence of collateral circulation)
• fever, nausea, vomiting, flank pain
• leukocytosis, elevated AST, ALP
• marked elevated LDH (LDH >4 times upper limit of normal with minimal elevations in AST/ALT strongly suggestive)
• acute onset hypertension (activation of RAAS) or sudden worsening of long-standing hypertension
• renal dysfunction, i.e. elevated Cr (if bilateral, or solitary functioning kidney)

Question 5

Ix of acute renal artery occlusion/infarct

Answer 5

• renal arteriography (more reliable but risk of atheroembolic renal disease)
• contrast-enhanced CT or magnetic resonance angiography, duplex Doppler studies (operator dependent)

Question 6

Rx of acute renal artery occlusion/infarct

Answer 6

• anticoagulation, thrombolysis, percutaneous angioplasty or clot extraction, surgical thrombectomy
• medical therapy in the long-term to reduce risk (e.g. antihypertensives)

Question 7

Define renal artery stenosis/ischaemia

Answer 7

chronic renal impairment secondary to hemodynamically significant renal artery stenosis or microvascular disease

• significant cause of ESRD: 15% in patients over 50 yr old (higher prevalence if significant vascular disease)

Question 8

Causes of renal artery stenosis/ischaemia

Answer 8

• usually associated with large vessel disease elsewhere
• causes of renal artery stenosis:
○ atherosclerotic plaques (90%): proximal 1/3 renal artery, usually males >55 yr, smokers
○ electrolytes, osmolality (gently rehydrate when needed, i.e. CHF)
○ fibromuscular dysplasia (10%): distal 2/3 renal artery or segmental branches, usually young females (typical onset

Question 9

Px of renal artery stenosis/ischaemia

Answer 9

• severe/refractory HTN and/or hypertensive crises, with negative family history of HTN
• asymmetric renal size
• epigastric or flank bruits
• spontaneous hypokalemia (renin activation in under-perfused kidney)
• increasing Cr with ACEI/ARB
• flash pulmonary edema with normal LV function

Question 10

Ix of renal artery stenosis/ischaemia

Answer 10

• must establish presence of renal artery stenosis and prove it is responsible for renal dysfunction
• duplex Doppler U/S (kidney size, blood flow): good screening test (operator dependent)
• digital subtraction angiography (risk of contrast nephropathy)
• CT or MR angiography (effective noninvasive tests to establish presence of stenosis, for MR avoid gadolinium contrast if eGFR

Question 11

Rx of renal artery stenosis/ischaemia

Answer 11

• surgical: percutaneous angioplasty ± stent, surgical revascularization, occasionally surgical bypass
• medical: BP lowering medications (ACEI is drug of choice if unilateral renal artery disease but
contraindicated if bilateral renal artery disease)
• little or no benefit if therapy is late i.e. kidney is already shrunken (however, therapy can be
considered to save the opposite kidney if normal)

Question 12

Risk Factors of renal artery stenosis/ischaemia

Answer 12

• > 50 yr old
• smoking
• other atherosclerotic disease (dyslipidemia, diabetes, diffuse atherosclerosis)

Question 13

Causes of renal vein thrombosis

Answer 13

• hypercoagulable states (e.g. nephrotic syndrome, especially membranous), ECF volume
depletion, extrinsic compression of renal vein, significant trauma, malignancy (e.g. RCC), sickle cell disease
• clinical presentation determined by rapidity of occlusion and formation of collateral circulation

Question 14

Px of renal vein thrombosis

Answer 14

• acute: nausea/vomiting, flank pain, hematuria, elevated plasma LDH, ± rise in Cr, sudden rise in proteinuria
• chronic: PE (typical first presenting symptom), increasing proteinuria and/or tubule dysfunction

Question 15

Ix of renal vein thrombosis

Answer 15

• renal venography (gold standard), CT or MR angiography, duplex Doppler U/S

Question 16

Rx of renal vein thrombosis

Answer 16

• thrombolytic therapy ± percutaneous thrombectomy for acute RVT
• anticoagulation with heparin then warfarin (1 yr or indefinitely, depending on risk factors)

Question 17

What are the 4 types of small vessel disease of kidney?

Answer 17

1. HYPERTENSIVE NEPHROSCLEROSIS
2. ATHEROEMBOLIC RENAL DISEASE
3. THROMBOTIC MICROANGIOPATHY
4. CALCINEURIN INHIBITOR NEPHROPATHY

Question 18

Definition of atheroembolic renal disease

Answer 18

progressive renal insufficiency due to embolic obstruction of small and medium-sized renal vessels by atheromatous emboli

Question 19

Causes of atheroembolic renal disease

Answer 19

spontaneous or after renal artery manipulation (surgery, angiography, percutaneous angioplasty)

anticoagulants and thrombolytics interfere with ulcerated plaque healing and can worsen disease

Question 20

Ix of atheroembolic renal disease

Answer 20

• eosinophilia, eosinophiluria and hypocomplementia
• renal biopsy: needle-shaped cholesterol clefts (due to tissue-processing artifacts) with surrounding tissue reaction in small/medium-sized vessels

Question 21

Rx of atheroembolic renal disease

Answer 21

no effective treatment; avoid angiographic and surgical procedures in patients with diffuse atherosclerosis, medical therapy for concomitant cardiovascular disease

Question 22

Prognosis of atheroembolic renal disease

Answer 22

poor overall, at least a third will develop ESRD

Question 23

Causes of thrombotic microangiopathy

Answer 23

etiologies include the spectrum of TTP-HUS, DIC, severe preeclampsia

Question 24

Renal involvement of thrombotic microangiopathy & its characterisation

Answer 24

• renal involvement more common in HUS than TTP

* renal involvement characterized by fibrin thrombi in glomerular capillary loops ± arterioles

Question 25

Rx of thrombotic microangiopathy

Answer 25

○ depends on cause
○ supportive therapy
○ TTP-HUS: plasma exchange, corticosteroids (splenectomy and rituximab if refractory)

avoid platelet transfusions and ASA

Question 26

Why is calcineurin inhibitor nephropathy important?

Answer 26

• major cause of kidney failure in other solid organ transplant (e.g. heart)

*Calcineurin inhibitors: suppress the immune system by preventing interleukin-2 (IL-2) production in T cells.

Question 27

Definition of calcineurin inhibitor nephropathy

Answer 27

• cyclosporine and tacrolimus

* causes both acute reversible and chronic, largely irreversible nephrotoxicity

Question 28

Causes of calcineurin inhibitor nephropathy

Answer 28

• acute: due to afferent and efferent glomerular capillary constriction leading to decreased GFR (tubular vacuolization)
○ pre-renal azotemia
• chronic: result of obliterative arteriolopathy causing interstitial nephritis and CRF (striped
fibrosis), less frequent now due to lower doses of calcineurin inhibitors

Question 29

Rx of calcineurin inhibitor nephropathy

Answer 29

Acute:
calcium channel blockers or prostaglandin analogs, reduce dose of cyclosporine
or switch to another immunosuppressive drug