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Urinary > Acute Kidney Injury > Flashcards

Acute Kidney Injury Flashcards

0
Q

What is oliguria?

A

Urine output of <400ml/day

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1
Q

What is AKI?

A

A sudden decline in renal function significant enough to produce uraemia and also often oliguria

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2
Q

What is used to classify a patient as having AKI?

A

Increased serum creatinine by greater than or equal to 26.5μmol/L within 48 hours
Increased serum creatinine by greater than or equal to 1.5 times the baseline within 7 days
Urine volume <0.5 ml/kg/hr

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3
Q

Pre renal causes of AKI? (General)

A

Impaired blood flow to the kidneys

Impaired autoregulation

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4
Q

What can impair blood flow to the kidneys causing pre-renal AKI?

A
  • hypovolaemia
  • low blood pressure
  • low cardiac output
  • vascular disease
  • systemic vasodilation (sepsis, cirrhosis, anaphylaxis)
  • cardiac failure (LV dysfunction, tamponade, valve disease)
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5
Q

What can cause impaired autoregulation causing AKI?

A

Pre-glomerular vasoconstriction

  • sepsis
  • hypercalcaemia
  • hepatomegaly syndrome

Drugs (NSAIDs)

Post-glomerular vasodilation

  • ACE inhibitors
  • angiotensin II antagonists
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6
Q

General intrarenal causes of AKI?

A

Acute tubular necrosis
Glomerular and arteriolar disease
Acute tubule interstitial nephritis

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7
Q

What is acute tubular necrosis caused by?

What happens?

A

Severe acute ischaemia
Nephrotoxins damage epithelial cells lining the tubules, causing cell death and shedding into the lumen
Can be caused by endogenous or exogenous factors

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8
Q

What are some nephrotoxic drugs which can lead to acute tubular necrosis?

A

Gentamicin
ACE-inhibitors
Angiotensin receptor blockers
NSAIDs

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9
Q

How can NSAIDs lead to AKI?

A

Inhibit production of prostaglandins
Prostaglandins normally cause vasodilation of afferent arteriole
Afferent arteriole has unopposed vasoconstriction
Reduced glomerular perfusion pressure
Ischaemia
Acute tubular necrosis
AKI

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10
Q

What is glomerular and arteriolar disease?

A

An immune disease affecting the glomerulus
Types include
-acute glomerulonephritis
-acute tubulointerstitial nephritis

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11
Q

What happens in acute glomerulonephritis?

A

Immune disease affecting glomerulus
Primary only affects kidneys
Secondary - kidneys involved as part of a systemic process eg SLE, vasculitis

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12
Q

What happens in acute tubulo-interstitial nephritis?

A

Inflammation of kidney interstitium
Infection - acute pyelonephritis (ascending bacterial infection)
Toxin induced - drugs

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13
Q

What is post-renal AKI?

A

Indicates obstruction to urine flow after urine has left tubules
(10% of AKIs)

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14
Q

What can obstruct urine outflow and cause AKI and where?

A

Within the lumen

  • canaliculi - renal pelvis, ureters, neck of bladder, urethra
  • blood clot
  • papillary necrosis
  • tumour of renal pelvis, ureter or bladder

Within the wall

  • congential - pelviureteric neuromuscular dysfunction, megaureter neurogenic bladder
  • ureteric stricture - usually causes chronic not acute

Pressure from outside

  • prostatic hypertrophy
  • malignancy
  • aortic aneurysm
  • diverticulitis
  • accidental ligation of ureter in surgery
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15
Q

What is anuria?

A

No urine - less than 100ml/day

16
Q

How can sodium be used in diagnosing the type of AKI?

A

Sodium is reabsorbed in pre-renal AKI to restore volume

Reduced in renal AKI due to tubular cell damage

17
Q

What is used to calculate sodium for AKI?

A

FEna (fractional sodium excretion)

(Urine Na ➗ plasma Na)
(Urine Cr ➗ plasma Cr) ✖️100

Pre renal if FEna 1%

18
Q

What is seen in cardiac failure? (Would indicate pre-renal AKI)

A 
Gallop rhythm
Raised BP
Raised JVP
Pulmonary oedema (basal crackles and dyspnoea)
Peripheral oedema (sacral/ankle)
19
Q

What would indicate sepsis (pre-renal cause)

A 
Pyrexia
Rigors
Bounding pulse
Vasodilation - warm peripheries
Rapid capillary refill
Hypotension
20
Q

What would indicate a urinary tract obstruction?

A 
Anuria
Single functioning kidney
History of renal stones/prostatism/pelvic or abdominal surgery
Palpable bladder
Pelvic/abdominal mass
Enlarged prostate (DRE)
21
Q

What serum biochemistry markers would indicate AKI?

A

Raised creatinine
Raised urea
Raised potassium
Raised phosphate

Low sodium
Low calcium

22
Q

Why would you use an ECG for diagnosis of AKI?

A

Look for hyperkalaemia

23
Q

What ECG changes are there in hyperkalaemia?

A 
Tall T waves
Small/absent P waves
Increased PR interval
Wide QRS complex
Sine wave pattern
Asystole
24
Q

What would you look for in AKI with a urine dipstick?

A

Blood
Protein
Leukocytes

25
Q

What would you see in microscopy of urine in AKI?

A

Pre-renal - hyaline cast
Acute tubular necrosis - muddy brown cast
Rapid progressive glomerulonephritis - RBC casts

26
Q

What are hyaline casts?

A

Aggregations of proteins seen in concentrated urine

27
Q

What soluble immunological tests would you have for AKI?

A

Circulating antibodies

  • Anti-nuclear antibody - SLE
  • anti-neutrophil cytoplasmic antibody - systemic vasculitis
  • anti-glomerular basement membrane antibodies - Goodpasture’s disease
28
Q

What imaging would you do to diagnose AKI?

A

Ultrasound - renal size, hydronephrosis, obstruction

CXR - pulmonary oedema

29
Q

When would histology be done with AKI?

A

Biopsy where pre and post-renal AKI have been excluded

Confident diagnosis of ATN cannot be made or systemic inflammatory sings or symptoms are present

30
Q

Treatment of pre-renal AKI?

A

Volume correction

  • hypovolaemia -> fluids
  • heart failure -> diuretics
31
Q

Treatment of acute tubular necrosis?

A

Supportive - maintain good kidney perfusion, avoid nephrotoxins

32
Q

Treatment for post-renal AKI?

A

Urological intervention to re-establish urine flow

33
Q

Overall, how would you treat AKI?

A

Avoid nephrotoxins
Restrict dietary sodium to avoid volume overload
If hyperkalaemia - stop potassium soaring diuretics, dextrose, insulin, β2 agonists
If there is acidosis - restrict protein, give NaHCO3

34
Q

What would indicate the need to go onto dialysis?

A

When kidneys can no longer adequately exerts Na and Cl, water, K+
Metabolic acidosis and NaHCO3 not appropriate
Presence of nephrotoxic which is dialysable eg aspirin overdose, ethylene glycol
Signs of uraemia - pericarditis, reduced consciousness, intractable nausea and vomiting

35
Q

What is rapidly progressive glomerulonephritis?

A

When glomerular injury is so severe, renal function deteriorates in days

36
Q

How may a patient present with rapidly progressive glomerulonephritis?

A

Uraemia emergency
Evidence of extra renal disease
Associated with crescetic glomerulonephritis

37
Q

What is required for diagnosis of rapidly progressive glomerulonephritis?

A

Renal biopsy

Urinary (19 decks)

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