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Renal > AKI > Flashcards

AKI Flashcards

1
Q

What is the definition of an acute kidney injury?

A

A syndrome of decreased renal function, measured by serum creatinine or urine output, occuring over hours - days

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2
Q

What staging systems are used to stage AKI?

A
  • KDIGO
  • RIFLE
  • AKIN
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3
Q

What is classed as stage 1 AKI based on the KDIGO classfication criteria (creatinine and urine output)?

A
  • Creatinine - 1.5-.1.9 x baseline OR >26.5 umol/L increase
  • Urine output - <0.5 ml/kg/h for 6-12 hrs
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4
Q

What is classed as stage 2 AKI based on the KDIGO classfication criteria (creatinine and urine output)?

A
  • Creatinine - 2.0-2.9 x baseline
  • Urine output - <0.5 ml/kg/h for >12 hrs
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5
Q

What is classed as stage 3 AKI based on the KDIGO classfication criteria (creatinine and urine output)?

A
  • Creatinine - >3.0 x baseline
  • Urine output - <0.3 ml/kg/h for >24 hrs or anuria > 12 hrs
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6
Q

What are pre-renal causes of AKI?

A

Various causes of reduced renal perfusion

  • Hypotension of any cause - MI, Heart Failure
  • Volume depletion - Hypovolaemia, Haemorrhage, Burns, Third spacing of fluid,
  • Sepsis
  • Renovascular disease
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7
Q

What are renal causes of AKI?

A
  • Glomerular - GN
  • Tubular - Acute tubular necrosis,
  • Interstitial - Interstitial nephritis, Sarcoidosis
  • Vascular - Vasculitis, HUS, DIC, TTP, Scleroderma crisis
  • Drug reaction
  • Infection
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8
Q

What are post-renal causes of AKI?

A

Obstruction of the urinary outflow tract

  • Retroperitoneal fibrosis
  • Lymphoma
  • Tumour
  • Prostate hyperplasia
  • Strictures
  • Renal calculi
  • Ascending urinary infection (including pyelonephritis)
  • Urinary retention
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9
Q

Why can hypoperfusion lead to an AKI?

A

Renal response to a lower perfusion pressure = enhance Na+ and H2O re-absorption

  • Baroreceptors respond to low BP (sympathetic stimulation) + vasoconstriction of the glomerular efferent arteriole and dilation of the afferent arteriole, attempts to maintain GFR within a relatively narrow range
  • Decreasing perfusion promotes activation of the RAAS + hypothalamic ADH secretion -> sodium and water retention
  • Decreased perfusion can precipitate acute tubular necrosis due to ischaemia
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10
Q

What is acute tubular necrosis?

A

Death of tubular epihelial cells resulting most often from renal ischaemia but can also be caused by direct renal toxins including drugs such as the aminoglycosides, lithium and platinum derivatives

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11
Q

What are causes of acute tubular necrosis?

A
  • Haemorrhage
  • Burns
  • Diarrhoea/vomiting
  • Pancreatitis
  • Diuretics
  • MI/CCF
  • Endotoxic shock
  • Snake bite
  • Myoglobinaemia
  • Hepatorenal syndrome
  • Renal contrast
  • Pre-eclampsia/eclampsia
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12
Q

What drugs can cause acute tubular necrosis?

A
  • Aciclovir
  • NSAIDs
  • Lithium
  • Amphotericin
  • Cisplatin
  • Vancomycin
  • Cyclosporin
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13
Q

What are the top 7 commonest causes of AKI in the UK?

A
  1. Sepsis
  2. Major surgery
  3. Cardiogenic shock
  4. Other hypovolaemia
  5. Drugs
  6. HRS
  7. Obstruction
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14
Q

What symptoms may be present in someone with an AKI?

A

History of pre-renal/renal/post-renal cause. May also have:

  • Oliguria/anuria
  • Vomiting
  • Dizziness
  • Symptoms of sepsis
  • Symptoms of CCF/MI - Orthopnoea/PND/SOB
  • Syncope
  • Haematuria - obstruction
  • Symptoms of uraemia - Pruritis, Anorexia, vomiting etc
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15
Q

What signs may be present in someone with an AKI?

A
  • Hypo/hypertension
  • Pulmonary oedema
  • Peripheral edema
  • Signs of uraemia - asterixis/altered mental status
  • Signs of precipitant - haemorrhage, sepsis, surgery
  • Abdominal bruit - renovascular disease
  • Full bladder - prostatic obstruction
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16
Q

What investigations would you consider doing in someone who you suspected had an AKI?

A
  • Bedside - Urine dipstick, urine output, basic observations, fluid balance
  • Bloods - FBC, U+E’s, VBG, LFTs, ESR/CRP, BC, Vasculitis screen, CK
  • Imaging - Renal USS, CXR, AXR, ECG, CT/MRI KUB, Cystoscopy
  • Other - renal biospy, urine culture, urine sodium, urine/serum creatinine ratio, urine/serum osmolality, urine osmolality
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17
Q

What might you see on U+E’s in someone with an AKI?

A
  • Acutely elevated serum creatinine
  • Hyperkalaemia
  • Uraemia
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18
Q

What might you see on FBC in someone with AKI?

A
  • Anaemia - CKD, blood loss
  • Leukocytosis - infection
  • Thrombocytopenia - HUS, TTP
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19
Q

What might you see on urine dipstick in someone with AKI?

A
  • Blood
  • WBCs
  • Proteinuria
  • Positive nitrite and leukocyte esterase (in cases of infection)
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20
Q

If someone presented with features of an AKI, what would you want to establish when initially assessing them?

A

ABCDE + assessment for any life-threatening complications:

  • NEWS score
  • Signs of Pulmonary oedema
  • Hyperkalaemia
  • Hypovolaemia
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21
Q

How would you quickly assess if somoene had AKI from obstruction?

A

Uruinary catheterisation

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22
Q

How long after acute tubular necrosis ocurs does recovery start to occur?

A

7-21 days

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23
Q

What metabolic disturbance may you see on VBG in someone with AKI?

A

Metabolic acidosis - unless acid is lost by vomiting/aspiration of gastric conetns

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24
Q

What general diagnostic approach would you take to diagnosing AKI?

A

Ask the following questions:

  • Is it acute or Chronic failure?
  • Is there an obstruction?
  • Is there a rare cause? - myeloma, vasculitis, HUS
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25
Q

What are symptoms of uraemia?

A
  • Anorexia
  • Nausea
  • Vomiting
  • Pruritus
  • Intellectual clouding
  • Drowsiness
  • Fits
  • Coma
  • Haemorrhagic episodes
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26
Q

What signs may point to a pre-renal cause of AKI?

A

Signs of dehydration/fluid depletion:

  • Hypotension
  • Hypovolaemia
  • Orthostatic hypotension
  • Tachycardia
  • Decreased JVP
27
Q

What signs may indicate that an AKI is caused by an intrinsic renal problem?

A
  • Hypertension
  • Physical signs of systemic disease - e.g. vasculitic rash, signs of myeloma etc.
28
Q

What signs may indicate a postrenal cause of AKI?

A
  • Distended bladder
  • Enlarged prostate
29
Q

What symptoms might indicate a pre-renal cause of AKI?

A
  • Thirst
  • Weight loss
  • Potential for volume loss - haemorrhage, surgery
30
Q

What features in the history may point to a renal cause of AKI?

A
  • Previous abnormal urinalysis
  • Exposure to toxins
  • Change in medications
31
Q

What features in the history may indicate a post-renal cause of AKI?

A
  • Frequency
  • Hesitancy
  • Nocturia
  • History of stones/neoplasm
  • Renal colic - esp if in one kidney
32
Q

What might you find on investigation of urine sodium in prerenal AKI?

A

Sodium <20 mmol/L

33
Q

What might you find on inveestigation of urine osmolality in someone with prerenal AKI?

A

>500 mOsm/kg H20

34
Q

What might you find on investigation of urine osmolality in someone with renal AKI?

A

>350 mOsm/kg H20

35
Q

What might you find on investigation of urine sodium in renal AKI?

A

Sodium >40 mmol/L

36
Q

What might you find on investigation of urine/serum creatinine ratio in someone with prerenal AKI?

A

>40

37
Q

What might you find on investigation of urine/serum creatinine ratio in someone with renal AKI?

A

<20

38
Q

What might you find on investigation of urine/serum osmolality in someone with prerenal AKI?

A

>1.5

39
Q

What might you find on investigation of urine/serum osmolality in someone with renal AKI?

A

<1.2

40
Q

Why might you perform a CXR to investigate AKI?

A

Look for signs of heart failure

41
Q

Why might you do renal US scan in someone with AKI?

A

Evaluation of post-obstructive causes

  • Dilated renal calyces (suggesting obstruction)
  • Reduced corticomedullary differentiation
  • Small and sclerotic-appearing kidneys (suggesting CKD)
42
Q

What might a high urine osmolality indicate in someone with AKI?

A

Pre-renal cause

43
Q

What might a urine osmolality close to serum osmolality indicate in AKI in terms of cause?

A

Acute tubular necrosis

44
Q

What might a low urine sodium concentration (<20 mmol/L) indicate in terms of cause of AKI?

A

Pre-renal cause - due to increased sodium resorption

45
Q

What would a high urinary sodium concentration indicate in terms of cause of AKI?

A

Renal cause - not able to reabsorb sodium

46
Q

Why might you perform an ECG in someone with AKI?

A

Look for signs of hyperkalaemia

47
Q

What might you find on renal biopsy of someone with an AKI?

A

Changes associated with Renal causes, e.g.

  • Acute tubular necrosis
  • Glomerulonephritis
  • Vasculitis
48
Q

What type of metabolic acidosis may be present in someone with AKI - high anion gap or normal anion gap?

A

High anion gap

49
Q

What changes might you see in plasma calcium and phsophate levels in AKI?

A
  • Increased phosphate
  • Decreased calcium
50
Q

How would you manage someone with an AKI?

A
  1. ABCDE - initial assessment
  2. Monitoring - fluid balance, Bloods, NEWS, ABG (if septic)
  3. Determine cause and treat
  4. Stop causative drugs/drugs that may cause complications
  5. Manage complications - hyperkalaemia, pulmonary oedema, sepsis
  6. Nutritional support - normal calorie intake
51
Q

What main things would you want to address in the management of a pre-renal AKI?

A
  • Correct volume depletion
  • Increase renal perfusion
  • Treat sepsis (if present)
52
Q

What main things woul dyou want to consider in the management of post-renal AKI?

A
  • Urinary catheter insertion/Consider nephrostomy
  • Treat cause - Urological intervention
53
Q

What are features of hypovolaemia?

A
  • Hypotension
  • Oliguria
  • Non-visible JVP
  • Poor tissue turgor
  • Tachycardia
  • Daily weight loss
  • Prolonged CRT
54
Q

What are features of fluid overload?

A
  • Hypertension
  • Increased JVP
  • Lung crepitations
  • Peripheral oedema
  • Gallop rhythm
55
Q

When would JVP not represent intravascular volume?

A

Right sided heart disease/failure

56
Q

How would you manage hypovolaemia in AKI?

A

Fluid resuscitation:

  • 500 ml crystalloid over 15 mins
  • Reassess
  • Consider futher boluses - 250-500 ml
  • Stop when euvolaemic/2L
57
Q

How would you manage hypervolaemia in someone with AKI?

A
  • Oxygen
  • Monitor weight
  • Fluid restriction
  • Consider Diuretics - can still work
  • Consider RRT
58
Q

When would you consider RRT in someone with AKI?

A

AEIOU

  • Acidosis – metabolic acidosis with a pH <7.1
  • Electrolytes – refractory hyperkalemia with a serum potassium >6.5 mEq/L or rapidly rising potassium levels; see previous post for a review of the causes and management of hyperkalemia
  • Intoxications – use the mnemonic SLIME to remember the drugs and toxins that can be removed with dialysis: salicylates, lithium, isopropanol, methanol, ethylene glycol
  • Overload – volume overload refractory to diuresis
  • Uremia – elevated BUN with signs or symptoms of uremia, including pericarditis, neuropathy, uremic bleeding, or an otherwise unexplained decline in mental status (uremic encephalopathy)
59
Q

How could you manage acidosis in AKI?

A
  • Treat cause
  • Consider Sodium bicarbonate - need adequate ventilation due to increased CO2 production
60
Q

What dietary restrictions would you consider in the management of AKI?

A

Restrict sodium and potassium intake

61
Q

When would you refer someone with an AKI to the renal team?

A
  • AKI not responding to treatment
  • AKI with complications - Hyperkalaemia, acidosis, fluid overload
  • Stage 3 AKI
  • AKI with difficult fluid balance
  • AKI due to intrinsic renal disease
  • AKI with hypertension
62
Q

What is important to know when refering someone with an AKI to the renal team?

A
  • Creatinine trend and pre-morbid result if available
  • Bicarb/Lactate
  • Hb
  • Platelets
  • Urine dipstick (before catheter)
  • NEWS Score
  • Fluid input/output
  • Clinical signs
  • Comorbiditiy
  • Drugs
63
Q

What might an elevated CK indicate as the cause of AKI?

A

Rhabdomyolysis

64
Q

What is the most common cause of AKI?

A

Pre-renal failure +/- ATN

Renal (19 decks)

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