AKI - Acute Kidney Injury

Question 1

What is the best method of assessing kidney function. What is the normal range

Answer 1

GFR or eGFR: Normal = 100-120

Question 2

State the causes of Pre-renal AKI (10)

Answer 2

Reduced blood flow
Absolute: Diarrhea, vomiting, severe burns, major hemorrhage, dehydration
Relative: Distributive shock (sepsis), Adrenal insufficiency, CCF, ACE inhibitors, renal artery stenosis, embolus

Question 3

What is azotemia?

Answer 3

increased nitrogen products in the blood => increased urea

Question 4

What is the normal urine output range?
What is considered reduced or oliguria?
What is considered severe?

Answer 4

Normal = 0.5-2ml/kg/hr
Oliguria = <0.5ml/kg/hr
Severe <0.3ml/kg/hr

Question 5

Define AKI

Answer 5

reduced renal function leading to increased serum creatinine and/or reduced urine output (<0.5ml/kg/hr)

Question 6

Urea may deposit in the skin causing skin discoloration. What color is it? In severe uremia what does it become?

Answer 6

Grey-yellow colour
Severe = Uremic frost (white flakes)

Question 7

State the signs and symptoms of uremia

Answer 7

Nausea, dizziness, anorexia
Encephalopathy: Asterixes, confusion, disturbed sleep
Pruritis with scratch marks
Skin discoloration (grey-yellow discoloration)
Pericarditis - Pericardial rub

Question 8

Uremia may eventually lead to pericarditis. What finding would support this? Describe the finding

Answer 8

Pericardial rub. scratchy creaky sounds like rubbing leather.
Heard loudest over left sternal border (2-3 intercostal space)

Question 9

Rash in the setting of oliguria. What are your differentials

Answer 9

HUS - hemolytic uremic syndrome
HSP (IgA vasculitis)
SLE
Sepsis

Question 10

What are the risk factors for an AKI?

Answer 10

5 on your HANDS Mneumonic
Hypertension
Age
Nephrotoxins - Aminoglycosides, heavy metals (Lead), ethylene glycol, myoglobin (increased CPK in rhabdomyolysis), uric acid (tumor lysis syndrome), tetracycline, IV contrast, ACE inhibitors
Diabetes
Systolic BP<90 (hypotension)

Question 11

What is tumor lysis syndrome and with relation to the kidney what may it cause?
What other acute condition may it cause? How is it treated?

Answer 11

Tumor lysis syndrome is caused by the quick turnover of cells typically occurring in chemotherapy. This leads to the release of high amounts of uric acid leading to Acute tubular necrosis.

High serum uric acid levels may also cause gout. This is treated acutely with Colchicine + hydration and chronically (preventative) with Allopurinol + hydration

Question 12

Give 5 causes of intra-renal AKI

Answer 12

Acute Tubular Necrosis
Glomerulonephritis
Acute interstitial nephritis
Hepatorenal syndrome
HUS - Hemolytic uremic syndrome
TTP - Thrombotic Thrombocytopenic Purpura

Question 13

How would you differentiate between a Pre-renal cause and Acute Tubular Necrosis?

Answer 13

We use serum BUN and urinalysis with sedimentation examination
Pre-renal vs ATN
BUN or urea creatinine ratio in serum: >20:1 vs Normal or <15
FeNA: <1% vs >2%
Urine Na: <20 vs >35 mEq/L
Urine osmolality: >500 vs <350 mosm/kg
Casts: None vs Brown, muddy cell casts (epithelia)

Question 14

Acute Tubular Necrosis:
What are the causes?
Explain the pathophysiology

Answer 14

Causes:
Ischemia => any pre-renal cause
Nephrotoxins => Aminoglycosides, heavy metals (lead), myoglobin, Uric acid, Ethylene glycol

Pathophysiology:
Dead tubular cells (from ischemia or nephrotoxins) slough off and plug the tubule causing an obstruction which can produce brown cellular casts in urine. This leads to increased tubular pressure causing:
reduced GFR => Oliguria and Azotemia
reduced gradient of diffusion => Hyperkalemia and metabolic acidosis
Intrarenal damage => reduced reabsorption => increased elimination of Na, urea, and water

Question 15

Explain the pathophysiology of glomerulonephritis in the context of AKI

How would you SCREEN for GN?

Answer 15

Antibody deposition leads to the activation of the complement system (C3/C4) which recruits macrophages to attack the podocytes leading to increased permeability => Hematuria (micro) and Proteinura (<3.5g/day). This leads to
hypoalbuminemia => Oedema and HTN
reduced gradient => reduced GFR => Oliguria and azotemia

C3/C4, electrophoresis, ASOT

Question 16

What organism may cause Struvite stones?

Answer 16

Proteus

Question 17

Where does oedema typically begin?

Answer 17

Peripheries and facial swelling

Question 18

Type 1 hypersensitivity will recruit which type of cells?

Answer 18

Eosinophils

Question 19

Type 4 hypersensitivity will recruit which type of cells?

Answer 19

Neutrophils

Question 20

What immunoglobulin is associated with eosinophilia?

Answer 20

IgE

Question 21

What are your differentials for flank pain (and hematuria by default)?

Answer 21

UTI
Pyelonephritis
Kidney stones
Renal papillary necrosis
Acute interstitial nephritis

Question 22

What is Renal papillary necrosis?
What is it caused by (3)?
What does it present with?

Answer 22

It is the ischemia of papillae of the collecting ducts which transport urine to the calyces and into the ureters
Causes: Late interstitial necrosis, chronic analgesic use, diabetes, pyelonephritis, sickle cell disease
Presents with hematuria and flank pain

Question 23

Give the causes of Acute interstitial Nephritis
Explain the pathophysiology of Acute Interstitial nephritis

Answer 23

This is caused by a hypersensitivity reaction to penicillin, NSAIDs and Diuretics
It is a Type 1 and 4 hypersensitivity reaction leading to the recruitment of eosinophils and neutrophils respectively leading to eosinphilia, rash (IgE), oliguria
If the medications aren’t stopped, it may lead to Renal Papillary necrosis which may present with Hematuria and Flank pain

Question 24

Give 5 causes of Post-renal AKI
What is the main mechanism of kidney injury in these cases?

Answer 24

Compression: Intraabdominal tumours, prosatatic hyperplasia, prostatitis, prostate carcinoma
Blockage: Kidney stones, Struvite stones (proteus), blocked catheter
Neurogenic bladder

Main cause = obstruction leading to hydronephrosis. This mimics pre-renal early on (as obstruction) and intrarenal after (as it has caused damage to the renal cells)

Question 25

increased serum myoglobin is a cause of ATN. What disease may lead to this? What is the main investigation to confirm this?

Answer 25

Rhabdomyolysis which causes muscle injury leading to increased CK (this is the test) and myoglobin.

Question 26

What imaging would you conduct for a patient with AKI?

Answer 26

Renal Ultrasound and CXR

Question 27

What findings would you be looking for in AKI with renal US?

Answer 27

Hydronephrosis, ureter obstruction, hyperechoic in pyelonephritis (gas)

Question 28

Pulmonary oedema may occur in a range of diseases including AKI, CKD, and CCF. What imaging would you use to confirm this? and what findings would you be looking for?

Answer 28

CXR: ABCDE Mneumonic
Alveolar oedema => Bat wing
B-lines => pulmonary oedema
Cardiomegaly (more than half of the thoracic cavity in PA)
Dilated upper lobe vessels
pleural Effusions

Question 29

What ECG findings would be concerning in a patient with ATN?

Answer 29

Patient with ATN is at risk of hyperkalemia
ECG Changes : Tented T waves, flattened P waves, and widened QRS complex before ending with sine wave pattern and V.fib

Question 30

What grading scale would you use for AKI? What is it based on?

Answer 30

KDIGO
based on creatinine levels and urine output
1 = Creatinine 1.5-1.9x baseline, <0.5ml/kg/hr for <12 hrs
2 = Creatinine 2-2.9x baseline, <0.5ml/kg/hr for >12hrs
3 = Creatinine 3x baseline, <0.3 ml/kg/hr

Question 31

In AKI, what are the indications for Renal Replacement Therapy (RRT)?

Answer 31

AEIOU mnemonic
Acidosis => pH<7.1
Electrolyte imbalance => Hyperkalemia >7mmol/L or ECG change
Ingestion of toxins/poisons
fluid Overload despite dialysis use
Uremic symptoms (pruritis, confusion, anorexia, vomiting, asterixes)

Question 32

What diuretic would you use for pulmonary oedema or fluid overload?

Answer 32

Furosemide

Question 33

What are the complications of AKI?

Answer 33

Chronic renal failure
Hyperkalemia (>7)
Pulmonary Oedema (CXR ABCDE)