AKI

Question 1

Define AKI

Answer 1

1. increase in serum creatinine by 26.5 micromol/L within 48 hours
2. increase in serum creatinine by 1.5x basline within 7 days
3. urine volume <0.5ml/kg/hour for 6 hours

Question 2

what are the 3 mechanisms leading to AKI?

Answer 2

pre-renal failure
intrinsic renal failure
post-renal failure

Question 3

what is pre-renal AKI caused by?

Answer 3

reduction in renal perfusion

Question 4

what causes AKI?

Answer 4

when responses: myogenic response (afferent & efferent arterioles) & tubular glomerular (NaCl in DCT) feedback are overwhelmed

Question 5

what happens to myogenic response & tubular glomerular feedback in hypoperfusion? (pre-renal)

Answer 5

dilation of afferent arterioles with some constriction of efferent

Question 6

what are the main causes of pre-renal AKI?

Answer 6

reduced extracellular fluid volume

impaired renal autoregulation

Question 7

what are the main causes of reduced extracellular fluid volume leading to pre-renal AKI?

Answer 7

hypovolaemia
cardiac failure
systemic vasodilation

Question 8

what are the main causes of impaired renal autoregulation leading to pre-renal AKI?

Answer 8

afferent constriction

efferent dilation

Question 9

what are causes of hypovolaemia?

Answer 9

dehydration

massive blood loss

Question 10

what are causes of cardiac failure?

Answer 10

dysfunction of left ventricle

valve disease

Question 11

what is a cause of systemic vasodilation?

Answer 11

sepsis

Question 12

what are causes of afferent constriction leading to impaired renal autoregulation, and therefore pre-renal AKI? (decrease GFR)

Answer 12

sepsis (hypoperfusion of main organs)
hypercalcaemia (vasoconstrict vascular SM)
NSAIDS (block prostaglandins COX pathway)

Question 13

what is a cause of efferent dilation leading to impaired renal autoregulation and therefore pre-renal AKI? (decreases GFR)

Answer 13

ACE-inhibitors (normally AT-II potent vasoconstrictor, also breaksdown bradykinin - vasodilator)

Question 14

When does (ATN) acute tubular necrosis develop?

Answer 14

ATN occurs when pre-renal AKI not treated with fluids rapidly (most pre-renal AKI & ATN reversible)

Question 15

what is ATN?

Answer 15

not strictly necrosis, but cellular damage that leads to inability to absorb NaCl (nephron) and so reduced water reabsorption and therefore volume depletion

Question 16

what is a risk of aggressive fluid resuscitation?

Answer 16

volume overload risk

Question 17

what are the main tubular sites of injury in ATN?

Answer 17

zone between cortex and medullar (susceptible to hypoxia) - especially S3 of PCT and TaL (and also high O2 demand)

Question 18

what happens in pre-renal AKI due to decrease in renal blood flow??

Answer 18

actual GFR decreases
no cell damage, kidneys work hard (acidly reabsorb NaCl & H2O via RAAS & ADH release) to try and restore blood flow

Question 19

how do you treat pre-renal AKI?

Answer 19

fluid resuscitation (increase blood volume to try and increase perfusion to increase GFR)

Question 20

who are more likely to develop ATN?

Answer 20

patients who develop AKI who are also taking a nephrotoxic agent

Question 21

what are nephrotoxins?

Answer 21

damage to epithelial cells lining tubules

leading to cell death which sheds in the lumen

Question 22

what are the different types of nephrotoxins?

Answer 22

endogenous & exogenous

Question 23

what are examples of endogenous nephrotoxins?

Answer 23

myoglobin
nitrate
bilirubin

Question 24

what are examples of exogenous nephrotoxins?

Answer 24

endotoxin
x-ray contrast
drugs (ACE-I / NSAIDS)
other poisons (weed killers / antifreeze)

Question 25

what is rhabdomyolysis?

Answer 25

endogenous nephrotoxin muscle necrosis from crush injury (trauma to muscle) releases myoglobin which is filtered at glomerulus & is toxic to tubule cells

Question 26

Aside from nephrotoxins, what are other causes of intrinsic AKI?

Answer 26

1. acute tubulo-interstitial nephritis | 2. glomerular & arteriolar disease (acute glomerulonephritis)

Question 27

what is acute glomerulonephritis (glomerular & arteriolar disease)?

Answer 27

immune disease affecting glomeruli

Question 28

what are the causes of acute glomerulonephritis?

Answer 28

primary - only affects kidney | secondary - kidneys affected as part of systemic process

Question 29

what is an example of primary acute glomerulonephritis?

Answer 29

IgA nephropathy (intrinsic AKI)

Question 30

what are examples of secondary acute glomerulonephritis?

Answer 30

SLE | vasculitis (destroy blood vessels by inflammation)

Question 31

what is acute tubulo-interstitial nephritis?

Answer 31

inflammation of the interstitium surrounding the filtration apparatus

Question 32

what are causes of acute tubulo-interstitial nephritis?

Answer 32

infection | toxins

Question 33

what is an infection cause of acute tubulo-interstitial nephritis?

Answer 33

acute pyelonephritis (sudden and severe kidney infection, causes the kidneys to swell and may permanently damage them) - intrinsic AKI

Question 34

what does acute tubulo-interstitial nephritis look like under the microscope?

Answer 34

lots of infiltration of cells between glomerulus

Question 35

what is a toxic cause of acute tubulo-interstitial nephritis?

Answer 35

drugs e.g. antibiotics (gentamicin), NSAIDS, PPI

Question 36

what is the pathophysiology of post-renal failure?

Answer 36

(both kidneys blocked / only 1 functioning kidney) obstruction of urine outflow tract with continuous urine production, leading increase intraluminal pressure (within urinary tubes) --> dilation of renal pelvis (hydronephrosis), decreasing renal function

Question 37

what are classifications of causes of post-renal AKI?

Answer 37

within the lumen within the wall pressure from outside

Question 38

what are causes of post-renal AKI from within the lumen?

Answer 38

kidney, ureter, bladder | e.g. stones, blood clot, tumour

Question 39

what are causes of post-renal AKI from within the wall?

Answer 39

stricture (post TB), congenital megaureter | usually CKD

Question 40

what are causes of pressure from outside leading to post-renal AKI?

Answer 40

enlarged (hypertrophy) prostate tumour aortic aneurysm ligation of ureter (tying of ureter)

Question 41

how do renal & ureteric stones cause post-renal luminal AKI? (location of stones)

Answer 41

stone in BOTH renal pelvis / ureters obstructing 1 kidney neck of bladder urethra

Question 42

stones of which size won't pass through urinary tract?

Answer 42

>10mm

Question 43

how do patients with renal & ureteric stones present?

Answer 43

pain | haematuria

Question 44

which age group is post-renal AKI more common in?

Answer 44

elderly (think about prostate enlargement)

Question 45

what are causes of pre-renal failure? (leading to decrease in blood supply via renal artery to kidneys afferent arterioles)

Answer 45

HF cirrhosis volume depletion

Question 46

what are causes of renal AKI?

Answer 46

renal artery / vein occlusion

Question 47

what are causes of renal parenchymal AKI?

Answer 47

1. intrarenal vascular (segmental, interlobar, arcuate, interlobular, afferent, efferent, vasa rectar / peritubular capillaries) 2. glomerulonephritis 3. acute tubular necrosis (toxic / ischaemia) 4. interstitial disease (tissue of kidney) 5. intrarenal obstruction (struvite stone)

Question 48

what is the main cause of post renal AKI?

Answer 48

urinary tract obstruction | e.g. stones, tumour, hypertrophic prostate

Question 49

why is it dangerous for hypertensive patients to be measured against out normal kidney functioning range?

Answer 49

hypertensive patient's baroreceptors are set to a higher setting from prolonged hypertension (>140/90), so their kidney functioning range set to a higher BP