Diseases Of Renal Vessels Flashcards Preview

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Flashcards in Diseases Of Renal Vessels Deck (18)
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1

Layers of blood vessels

(Innermost -> outermost)

1) tunica intima
- endothelium and thin subendothelial layer of loose CT
- * in arteries only, intima includes thin layer of internal elastic lamina

2) tunica media
- lots of smooth muscle and elastic fibers
- * in arteries may also present with a external elastic lamina layer

3) tunica externa
- connective tissues with type 1 fiber as and elastic fibers

2

Nephrosclerosis

Associated with renal arterioles and small artery sclerosis
- causes glomerulosclerosis and chronic tubulointerstital injuries.
- vessels are narrowed lumens and focal parenchyma ischemia

**strongly associated with HTN and diabetes

***more common in blacks and advanced age

3

Pathogenesis of nephrosclerosis

Two processes

1) medial and intima thickening
- response to hemodynamic changes, aging, genetic defects

2) hyalinization of arteriolar walls
- response to leakage of plasma proteins through injured endothelium and increased basement membrane matrix

4

Malignant nephrosclerosis

Renal vascular disorder associated with malignant or accelerated HTN

Really only affects younger patients who are male and black
- usually also only develops as a superimposed condition on preexisting essential HTN and underlying chronic renal disease

**leads to rapid renal failure from untreated malignant HTN

5

Malignant nephrosclerosis pathology

Almost always the initial insult is some form of vascular damage to the kidneys

Leads to fibriunoid necrosis of arterioles and small arteries with activation of intravascular thrombosis

Can also cause hyperplastic arteriolosclerosis if mitogenic factors cause hyperplasia of intima smooth muscle of vessels
- typical in malignant HTN

6

What system is often chronically stimulated in malignant nephrosclerosis?

RAAS
- the kidney is markedly ischemic which in turn makes the kidney think the overall blood pressure and volume in the body is low all the time

*this cycle further increases ischemia however since angiotensin-2 further vasoconstricts and renin further increases due to increased vasoconstriction*

7

Fibrinoid necrosis vs hyperplastic arteriolosclerosis

Fibrinoid necrosis
- cytology detail is lost within the vessel and the vessel wall takes on a smudgy eosinophilic appearance (due to fibrin deposition)
- NO inflammation

Hyperplastic arteriolitis
- looks line an “onion-skin”
- can show inflammation
- more often leads to renal failure

8

Clincial features of malignant nephrosclerosis

BP is >200/120

Shows:
- papilledema
- retinal hemorrhages
- symptoms of encephalopathy
- cardiovascular abnormalities
- symptoms of early renal failure
- marked proteinuria and hematuria

Treatment = intense aggressive HTN treatment to prevent irreversible renal injuries
- before current HTN drugs mortality was 50-90%
- now mortality is 30-50%

9

Thrombotic microangiopathies (TMA)

Lesions in various clinical syndromes

Primary forms:
- Shiga toxin-HUS, TTP and atypical HUS (complement mediated TMA)

Secondary forms:
- Malignant HTN and scleroderma-associated TMA

10

Classic laboratory findings in TMAs

- Thrombocytopenia
- Hemolytic anemia (microangiopathic)

Caused due to chronic platelet consumption and shearing mechanical damage to RBCs as they pass through the clot site (respectively)

11

Shiga toxin mediated HUS pathogenesis

** msot common cause of TMA (75% of TMAs are started after GI infection of Shiga toxin E. Coli

E. Coli Shiga toxin producing species causes HUS due to the Shiga toxin itself

Toxin causes endothelial damage and glomerular endothelial cell damage
- toxin activated increased endothelin and decreases nitric oxide production (both together promotes vasoconstriction and both platelet adhesion and activation)
- high does = cell death

**also produces thrombi sometimes which often get stuck in afferent arterioles of the kidney

12

Atypical HUS pathogenesis

Usually hereditary causes that dampen complement activation via the alternative pathway
- leads to excessive activation of complement and ensuing microvascular injury and microvascular thrombosis
- also activated MAC (target for therapeutic antibody action)

**no diarrhea**

13

(Thrombotic Thrombocytopenic Purpura) TTP pathogenesis

Inherited deficiencies of ADAMTS13 (plasma protease that cleaves vWF)
- inherited = mutations in the ADAMTS13 gene
- acquired = antibodies against ADAMTS13 gene

**both result in formation of abnormally large vWF multimers that activate platelets spontaneously and formation of thrombosis**

14

Shiga toxin associated HUS symptoms

Sudden onset of hematemesis, melena hematuria and severe oligouria.
- **almost always proceeds after a GI or flulike prodromal episode
- anemia and neurological changes are also seen

**is a main cause of AKI in children and most recover within weeks. However there is a 25% chance of developing renal insufficiency in 25 yrs**

15

Atypical HUS symptoms

Similar to Shiga toxin except there is **NO prodromal flu-like or GI infection

Treatment requires antibody inhibitors, plasmapheresis or liver transplant to cure
(so more aggressive and without this, usually provides a poorer outcome)

16

TTP symptoms

sudden onset but usually has dominant CNS symptoms and less oliguria/hematuria
- less kidney involvement than Shiga toxin and atypical HUS

10% survival without plasmapheresis

17

Renal artery stenosis

Unilateral = 2-5% of all HTN cases
- curable by surgery
- cause of secondary HTN (produces a chronic release of renin)
- need to give ACE-Is to keep HTN down

**most common cause is narrowing renal artery by atherosclerosis plaques (70%)**
- more common in men and advancing age and diabetes

***2nd most common cause is fibromuscular dysplasia (muscular layer getting idiopathically replaced by fibrosis scarring)***
- tends to occur in women in the 30-40s

18

What are the three groups of hypertensive patients with nephrosclerosis that one would be exceptionally worried about developing renal failure?

1) people of African descent

2) people with severe BP elevations (almost malignant levels)

3) persons with underlying comorbidities (especially diabetes mellitus)