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Acute Kidney Injury Flashcards

1
Q

What is the definition of ARF?

A

When renal function SUDDENLY decreases
That the patient can’t maintain fluid and electrolyte balance
And can’t excrete nitrogenous waste

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2
Q

What lab abnormalities help diagnose ARF?

A

Acute increase in creatinine

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3
Q

What are the clinical manifestations of ARF?

A
  1. Oliguria & fluid overload
    • pulmonary oedema > dyspnoea
  2. Uremia
    • vomiting
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4
Q

What are the 3 main causes of ARF? Which are more common amongst these?

A
  1. Pre-renal
  2. Intrinsic
  3. Post-renal

Pre-renal and intrinsic causes make up 90% of all ARF, post-renal only 10%

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5
Q

What are the pre-renal causes of ARF?

A

Perfusion or volume depletion

  • Perfusion: CCF, malignant/uncontrolled HTN
  • Volume depletion: dehydration, vomiting, diarrhoea, overdiuresis, sepsis, other shocks, third spacing of fluid from severe pancreatitis
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6
Q

What are the intrinsic causes of ARF?

A

ATN
Glomerulonephritis
Interstitial nephritis - drugs e.g. antibiotics, analgesics & NSAIDs

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7
Q

What specific group of antibiotics can cause ARF?

A

Aminoglycosides

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8
Q

What are the post-renal causes of ARF?

A

Urinary obstruction can be a result of stones, BPH, strictures.
Infection - pyelonephritis from ascending urinary tract infection.

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9
Q

What lab results suggest ARF?

A
  1. Electrolytes - hyperkalemia, hyper phosphatemia, hypocalcemia
  2. Increased urea and creatinine
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10
Q

Sepsis and ARF - how will the patient present?

A

Sepsis: fever, toxic-looking
ARF: acute rise in creatinine, rise in BUN

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11
Q

Dehydration and ARF - how will the patient present?

A

Dehydrated: thirsty, dry mucous membranes, altered mental status
Cap refill time increased, reduced skin turgor

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12
Q

Shock and ARF - how will the patient present?

A

Shock: hypotension and tachycardia

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13
Q

Acute glomerulonephritis results in increased urinary sodium. T/F?

A

True - acute GN affects concentrating ability > dilute urine > urinary Na high (Na goes where water goes)

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14
Q

ATN results in high urinary Na. T/F?

A

True - ATN, like acute GN affects concentrating ability > dilute urine > high urinary Na

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15
Q

Urinary Na is normal, <20mmol/L, differentials are narrowed down to which:

  1. Acute tubular necrosis
  2. Acute GN
  3. AIN
  4. Pre-renal azotemia
  5. Urinary tract obstruction
A

If urine Na is normal, concentrating ability is unimpaired, options 3 - 5 are possible differentials.
Only ATN and acute GN will affect concentrating ability resulting in dilute urine with high urinary Na concentration.

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16
Q

Urinary tract obstruction definitely results in normal urinary Na as concentrating ability is not affected. T/F?

A

False: urinary Na in the setting of urinary tract obstruction is variable. Concentrating ability may or may not be affected.

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17
Q

Urine osmolality >500mOsm/kg, differentials narrowed down to which:

  1. ATN
  2. Acute GN
  3. AIN
  4. Pre-renal azotemia
  5. Urinary tract obstruction
A

Urine osmolality >500mOsm/kg means urine is concentrated and concentrating ability is NOT affected, leaving options 3 and 4 possible.

  1. ATN 2. Acute GN affect concentrating ability, resulting in dilute urine > urine osmolality becomes <350.
  2. Urinary tract obstructed body will try to get rid of obstruction by peeing out more dilute urine frequently > low osmolality > less than 350mOsm/kg.
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18
Q

What are the causes of urinary tract obstruction within the lumen?

A

Stones
Crystalluria
Tumour
Papillary necrosis

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19
Q

What are the causes of urinary tract obstruction WITHIN the wall?

A

Neurogenic bladder (spasm)
Urethral stricture
Bladder neck stenosis

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20
Q

What are the causes of urinary tract obstruction outside the wall?

A

Cancer of surrounding structures i.e. colon, cervix, uterus, prostate
Constipation
BPH
Retroperitoneal fibrosis

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21
Q

Hx/Ex/Ix suggest post-renal cause of ARF > where might the urinary tract obstruction be? 3 places.

A

Within the lumen e.g. calculi
Within the wall e.g. neurogenic bladder
Outside the wall e.g. cancer

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22
Q

What are the clinical history and examination signs and symptoms that are relevant for ruling in post-renal cause of ARF?

A
  1. Haematuria - cancer
  2. Distended bladder - urinary tract obstruction
  3. Enlarged prostate on PR exam - obstruction
  4. LUTS - obstruction
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23
Q

What are LUTS?

A

Storage and voiding problems

  • Urgency, incontinence
  • Frequency, hesitancy. straining, dribbling
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24
Q

Urine microscopy shows muddy brown casts - what is your diagnosis for the patient’s cause of ARF?

A

Acute tubular necrosis

Muddy brown casts are characteristic of ATN and are a type of granular casts

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25
Intrinsic renal causes of ARF
By anatomy 1. Glomerular - Acute GN 2. Tubules - ATN 3. Interstitium - AIN
26
Acute interstitial nephritis is caused by?
Mostly nephrotoxic drugs e.g. antibiotics penicillin, aminoglycosides; analgesics, NSAIDs, PPIs
27
Urine osmolality is high >500mOsm/kg, what are the possible causes of ARF?
Things that don't involve glomerulus: 1. Pre-renal causes 2. AIN (instrinsic)
28
Urinary Na is high >20mmol/L, what are the possible causes of ARF?
Urine is diluted > concentrating ability affected > 1. Not pre-renal cause 2. Intrinsic - ATN and acute GN 3. Post-renal - obstruction may or may not affect urinary Na levels
29
What are the causes of acute GN?
Post-strep GN | IgA nephropathy - immune attack on glomerulus
30
Urine microscopy shows WBC casts and eosinophilia what is the cause of ARF?
WBC casts + eosinophilia > immunological reaction going on > attack kidneys > IgA nephropathy (intrinsic cause); immune reaction to strep antigens > post strep GN
31
Urinary sodium is >20, what are the causes of ARF?
>20 abnormal > unable to concentrate urine > ATN and acute GN
32
Components of urinalysis and what they mean
``` pH Specific gravity - concentration Glucose - diabetes Haemoglobin Myoglobin - rhabdomyolysis ```
33
A patient with ARF/AKI has a normal urinalysis with minimal cells and blood and no casts, what are the causes of ARF?
Pre-renal causes - volume depletion | Post-renal causes - obstruction
34
What do the different cells seen under urine microscopy suggest about the cause of ARF? 1. Granular casts + epithelial cells 2. RBC casts 3. WBC casts + eosinophils
1. Granular + epithelial cells - ATN 2. Acute GN 3. AIN - caused by IgA nephropathy, post-strep GN
35
What urine investigations to do for ARF?
1. UFEME - urine full examination microscopy elements | 2. Urine Na and osmolality
36
1. Urinary Na+ low and osmolality high - cause of AKI? | 2. Urinary Na+ high and osmolality low - cause of AKI?
1. concentrated urine - pre-renal causes of AKI | 2. tubular injury - ATN
37
How to differentiate ARF from CRF in FBC Ix?
CRF - will have anaemia > low Hb count ARF - no anaemia > normal Hb count Patients with CRF often have anaemia due to reduced erythropoietin synthesis by kidneys
38
Eosinophilia on FBC in a patient with ARF.
Eosinophilia > immune > AIN caused by IgA nephropathy etc.
39
Diagnosing AKI > did a FBC > what parameters are impt?
FBC 1. Anaemia - CRF instead of ARF 2. Eosinophilia - AIN (immune)
40
What is the basic physiologic basis of using BUN:creatinine ratio to determine the cause of ARF?
1. Urea is reabsorbed by tubules 2. Creatinine is NOT reabsorbed 3. In pre-renal causes the tubules are working so urea will be reabsorbed a lot, resulting in high urea content in the blood and high BUN:creatinine ratio of >100:1. 4. When the tubules are affected, such as in intrinsic renal damage, urea is not reabsorbed and the ratio falls to <40:1. 5. Ratio between 40:1 and 100:1, it can be normal renal function or post-renal cause of ARF.
41
What bloods to do for ARF?
1. FBC - Hb (anaemia - CRF) - Eosinophilia (Acute IN) 2. CKMM (rhabdomyolysis) 3. Electrolytes/urea/creatinine - Urea > crea
42
Diagnosing AKI > did a FBC > what parameters are impt?
FBC 1. Anaemia - CRF instead of ARF 2. Eosinophilia - AIN (immune)
43
What are the 3 KDIGO (indigo) criteria for diagnosing AKI?
1. Rise in serum creatinine by more than 50% in the last 7 days 2. Increase in serum creatinine by >0.3mg/dL or >26.5umol/L for 48 hours 3. Oliguria <0.5mL/kg/hr for more than 6 hours
44
What are the 3 stages of AKI defined by the KDIGO criteria?
Stage 1: 1. rise in serum creatinine by 1.5-1.9-fold 2. urine output < 0.5mL/kg/hr for 6-12 hrs Stage 2: 1. rise in serum creatinine by 2-to 2.9 fold 2. urine output < 0.5mL/kg/hr for more than 12 hrs Stage 3: 1. rise in serum creatinine by 3-fold 2. urine output < 0.5mL/kg/hr for more than 48 hrs 3. Need replacement therapy
45
What is the absolute increase in Cr considered as AKI?
>44umol/L
46
What can affect creatinine levels falsely?
1. Muscle mass 2. Rhabdomyolysis 3. Starvation 4. Nutrition & diet (protein intake) 5. Patient on antibiotics Bactrim (increased serum creatinine levels)
47
What is one type of AKI that has almost as high a mortality rate as ESRD?
Acute-on-chronic kidney disease
48
What are the types of dialysis treatments for AKI?
PD HD CRRT: continuous renal replacement therapy (used more in ICU settings)
49
Who is at risk of AKI?
1. Polypharmacy - NSAIDs, aminoglycosides, ACE I, lithium, anti-fungals, diuretics 2. Malignancy and chemotherapy 3. Organ failure: liver failure, respiratory failure and heart failure 4. Hypovolaemia and dehydration
50
What is one serious infective cause of AKI?
Sepsis
51
In the ED setting, someone's come in with suspected AKI what are the most urgent things to know?
1. Volume/fluid status - does this person need urgent resuscitation? 2. What is their baseline renal function? 3. Is it an acute kidney injury or acute-on-chronic picture? 4. What medications are they taking? 5. Urine sediment test
52
Pre-renal causes of AKI: apart from volume depletion what's the other major category?
Renovascular disease - Renal artery stenosis - Renal artery thrombosis
53
UFEME shows haemoglobin in urine - what is this patient's cause of AKI?
Rhabdomyolysis
54
UFEME shows granular casts - what is the cause of AKI in this patient?
Granular > tubular > ATN
55
UFEME shows red cell casts - what is the cause of AKI in this patient?
Acute GN | Glomerulus - vascular
56
UFEME shows eosinophils and white cell casts - what is the cause of AKI in this patient?
AIN | Eosinophils - two-headed nucleus cell
57
UFEME shows that urine osmolality is high and urine Na+ concentration is low > what is the cause of AKI in this patient?
Osmolality high > able to concentrate urine Na+ low > tubular reabsorption okay > 1. pre-renal 2. Acute GN
58
UFEME shows that urine osmolality is low and urine Na+ concentration is high > what is the cause of AKI in this patient?
Osmolality low > unable to concentrate urine Urine Na+ high > tubular reabsorption of water and Na+ impaired > 1. post-renal 2. Acute IN 3. Acute TN
59
When evaluating a patient with suspected AKI, the FBC shows eosinophilia > what is the cause of AKI?
Acute IN
60
What test to order if you suspect the patient has AKI because of rhabdomyolysis?
CK-MM
61
Patient with suspected AKI. Urea-creatinine ratio of 50:1 what is the cause of AKI?
Pre-renal, probably dehydration Dehydration causes increased urea reabsorption resulting in increased serum urea levels. > 10:1 suggest dehydration as a cause.
62
What are the things to screen for in an 'autoimmune screen' for a patient with suspected AKI to determine the cause?
1. Anti-glomerularBM antibody 2. ANCA 3. ANA 4. Complement levels 5. Anti-dsDNA
63
What imaging is useful to rule out/in urolithiasis as a cause of AKI?
Renal U/S KUB (X-ray) or CT KUB
64
Other than visualising obstruction, why is a renal ultrasound useful in the setting of AKI?
If see small atrophied kidneys, suggests that patient also has chronic renal disease > acute-on-chronic picture.
65
Renal ultrasound shows dilated calyces, ureters in a patient with AKI. What is the cause of his AKI?
Renal U/S shows hydronephrosis | Obstruction is the cause of his AKI
66
Patient comes in with suspected AKI > after bladder catherization his condition improves. What was the cause of his AKI?
Urethral obstruction

Nephrology (9 decks)

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