AKI

Question 1

Definition of AKI

Answer 1

• An increase in serum creatine above baseline levels

- A fall in urine output less than 400-500ml per 24 hours (oliguria)

Question 2

What are subtypes of AKI?

Answer 2

• Pre-renal: reduced perfusion of kidneys
• Post-renal: urinary tract obstruction
• Renal: intrinsic damage to renal structures

Question 3

What is auto regulatory arteriolar responses to reduced perfusion?

Answer 3

Myogenic relaxation of afferent arteriole to maintain renal blood flow and GFR

Question 4

What are THREE effects of RAAS in response to reduced perfusion?

Answer 4

1. Local action of angiotensin 2 differential vasoconstriction of EA and AA (assisted by prostaglandins)
2. Increased activity of aldosterone for sodium retention to maintain cardiac filling and tonicity of extracellular water
3. Release of ADH to concentrate urine to preserve intravascular volume

Question 5

What restricts GFR preservation in pre-renal phase?

Answer 5

• CKD
• Hypertension and diabetes
• Prostaglandin inhibitors
• Nephrotoxic medication

Question 6

What arteriolar diseases reduce auto regulation?

Answer 6

• Systemic hypertension and diabetes

Question 7

What are components of tubuloglomerular feedback?

Answer 7

• JG cells adjacent to afferent arteriole

- Macula densa cells of thick ascending limb of loop of Henle

Question 8

What is function of JG cells?

Answer 8

Produce renin in response to reduced renal perfusion or reduced tubular salt delivery

Question 9

What is function of macula densa?

Answer 9

Produce adenosine in response to increased salt delivery

Question 10

What is effect of Angiotensin 2 on glomerular pressure?

Answer 10

• Angiotensin 2 causes vasoconstriction of AA and EA

- Prostaglandin E2 reduces vasoconstrictive action of angiotensin 2 on AA

Question 11

What stimulates production of PGE2?

Answer 11

Angiotensin 2

Question 12

What are 6 effects of Angiotensin 2?

Answer 12

• Differential glomerular arteriolar vasoconstriction
• Aldosterone production to increase salt and water retention
• PGE2 production
• Stimulation of ADH release
• Increased permeability of filtration barrier in glomerulus
• Systemic vasoconstriction

Question 13

How does kidney turn off glomerular filtration?

Answer 13

1. Increased sodium delivery, due to failing proximal tubular function, to macula densa
2. Release of adenosine, which vasoconstrictor afferent arteriole to reduce glomerular capillary pressure and turn off glomerular filtration

Question 14

What is commonest cause of ATN?

Answer 14

Reduced renal perfusion

Question 15

What happens during ATN?

Answer 15

• Ischaemic tubular cell death occurs

- Glomerular filtration remains turned off by adenosine

Question 16

What does severe and sustained loss of perfusion lead to?

Answer 16

Irreversible injury to nephrons (cortical necrosis)

Question 17

What are causes of post-renal AKI?

Answer 17

• BILATERAL obstruction of kidneys (or bladder)

- Asymmetric function (single or dominant kidney)

Question 18

What is post obstructive diuresis?

Answer 18

• Urine outputs in excess of 500ml/hour
• Occurs after relief of complete obstruction due to effects of obstruction on concentrating capacity of kidney
• Usually reversible

Question 19

What are vascular causes of AKI?

Answer 19

• Vasculitis
• HUS
• thrombosis

Question 20

What are glomerular causes of AKI?

Answer 20

Nephritic syndrome

Question 21

What are commonest tubular causes of AKI?

Answer 21

ATN

Question 22

What are interstitial causes of AKI?

Answer 22

Allergic interstitial nephritis

Question 23

Mechanism of ATN

Answer 23

Hypoperfusion/medication (antibiotics) → cellular damage to tubule (ATN) → failing proximal tubule → increased salt delivery to macula densa → stimulate adenosine production → vasoconstriction of AA → reduce GFR

Question 24

What is allergic interstitial nephritis?

Answer 24

Acute inflammatory allergic reaction to an allergen

Question 25

What are causes of allergic interstitial nephritis?

Answer 25

• Antibiotics
• NSAIDS or COX inhibitor
• Proton pump inhibitor

Question 26

What is allergic interstitial nephritis associated with?

Answer 26

• Rash

- Oesinophilia