Acute Kidney Injury

Question 1

How is AKI defined?

Answer 1

Acute kidney injury has variably been defined as an abrupt deterioration in parenchymal renal function, which is usually, but not invariably, reversible over a period of days or weeks

Question 2

What percentage of people admitted to hospital and ICU develop AKI, respectively?

Answer 2

AKI is seen in 10-15% of people admitted to the hospital and in more than 50% of people admitted to the intensive care unit (ICU)

Question 3

How can causes of AKI be categorised?

Answer 3

Pre-renal, intrinsic/renal, post-renal

Question 4

What are common pre-renal causes of AKI?

Answer 4

1. Hypovolaemia (GI losses, burns, haemorrhage)
2. Reduced CO (Cardiac failure, liver failure, sepsis)
3. Drugs that reduce blood pressure, circulating volume or renal blood flow (ACE-I, ARBs, NSAIDs, loop diuretics)

Question 5

How would you define pre-renal causes of AKI?

Answer 5

Pre-renal causes of AKI are most common and are due to reduced perfusion of the kidneys and leading to a decreased glomerular filtration rate (GFR)

Question 6

How would you define renal causes of AKI?

Answer 6

Consequences of structural damage to the kidney, for example, tubules, glomeruli, interstitium, and intrarenal blood vessels.

Question 7

What are common renal causes of AKI?

Answer 7

1. Toxins and drugs
2. Antibiotics
3. Glomerular causes
4. Tubular causes
5. Interstitial causes

Question 8

What are glomerular causes of intrinsic AKI?

Answer 8

Glomerulonephritis

Question 9

What are tubular causes of intrinsic AKI?

Answer 9

Acute tubular necrosis, rhabdomyolysis, myeloma

Question 10

What are the interstitial causes of intrinsic AKI?

Answer 10

Interstitial nephritis, lymphoma infiltration

Question 11

What are the vascular causes of intrinsic AKI?

Answer 11

Vasculitis, thrombosis, thromboembolism, dissection

Question 12

What is acute tubular necrosis?

Answer 12

Acute tubular necrosis (ATN) is common, particularly in hospital practice.

It results most often from renal ischaemia but can also be caused by direct renal toxins including drugs such as the aminoglycosides, lithium and platinum derivatives

Question 13

How would you define post-renal causes of AKI?

Answer 13

Post-renal causes are least common, accounting for around 10% of acute kidney injury. Due to acute obstruction of the flow of urine resulting in increased intratubular pressure and decreased GFR

Question 14

What are common post-renal causes of AKI?

Answer 14

Obstruction –> renal stones, blocked catheter, enlarged prostate, genitourinary tract tumours/masses, neurogenic bladder

Question 15

What are the symptoms and signs of AKI?

Answer 15

Accumulation of urea and other nitrogen-containing substances in the bloodstream lead to a number of symptoms:

1. Fatigue
2. Loss of appetite
3. Headache
4. Nausea
5. Vomiting
6. Potassium level disturbances can lead to arrhythmias
7. Fluid balance is affected, leading to hyper, hypo or normotension
8. Pain in the flanks may be encountered in some conditions (such as clotting of the kidneys’ blood vessels or inflammation of the kidney)

Question 16

What is the clinical presentation of AKI determined by?

Answer 16

The clinical presentation is often dominated by the underlying cause. The various symptoms of acute kidney injury result from the various disturbances of kidney function that are associated with the disease.

Question 17

Which groups are specifically at risk of AKI?

Answer 17

1. People > 65 age
2. History of AKI
3. CKD with estimated glomerular filtration rate [eGFR] less than 60mL/min/1.73m2
4. Symptoms or history of urological obstruction or conditions which may lead to obstruction
5. Chronic conditions such as heart failure, liver disease, and diabetes mellitus.

Question 18

How is AKI diagnosed?

Answer 18

AKI can be diagnosed if any one of the following is present:
1. Increase in Serum Creatinine by ≥0.3mg/dl (≥26 μmol/l) within 48 hours; or

2. Increase in Serum Creatinine to ≥1.5 times baseline, which has occurred within the prior 7 days; or
3. Urine volume < 0.5 ml/kg/h for 6 hours

Question 19

When should you think AKI?

Answer 19

• Nausea and vomiting, or diarrhoea,evidence of dehydration.
• Reduced urine output or changes to urine colour.
• Confusion, fatigue,and drowsiness.

Especially in combination with any of the risk factors

Question 20

What are the three stages of AKI?

Answer 20

1. Stage 1 - risk
2. Stage 2 - injury
3. Stage 3 - failure

Question 21

What is the first stage in AKI?

Answer 21

STAGE 1 - risk

1. Creatinine rise of 26 micromol or more within 48 hours OR
2. Creatinine rise of 50–99% from baseline within 7 days (1.50–1.99 x baseline) OR
3. Urine output < 0.5 mL/kg/h for more than 6 hours

Question 22

What is the second stage in AKI?

Answer 22

STAGE 2 - injury

1. 100–199% creatinine rise from baseline within 7 days (2.00–2.99 x baseline) OR
2. Urine output < 0.5 mL/kg/hour for more than 12 hours

Question 23

What is the third stage in AKI?

Answer 23

STAGE 3 - failure

1. 200% or more creatinine rise from baseline within 7 days (3.00 or more x baseline) OR
2. Creatinine rise to 354 micromol/L or more with acute rise of 26 micromol/L or more within 48 hours or 50% or more rise within 7 days OR
3. Urine output < 0.3 mL/kg/hour for 24 hours or anuria for 12 hours

Question 24

What are the complications linked to AKI?

Answer 24

Complications from acute kidney injury (AKI) arise as a result of impairment of the kidney’s excretory, endocrine, and metabolic actions. The risk of complications is related to the stage of AKI

Complications include:

1. Hyperkalaemia
2. Electrolyte imbalance
3. Metabolic acidosis
4. Volume overload
5. Uraemia
6. CKD and end-stage renal disease

Question 25

What are the predictors of developing CKD after AKI?

Answer 25

Predictors for CKD after AKI include older age, lower baseline eGFR, higher baseline albuminuria, and higher stages of AKI

Question 26

How would you treat AKI?

Answer 26

Immediate admission or referral to hospital is not needed for all people with acute kidney injury (AKI).

Assess volume status, renal function, serum potassium

Treat the underlying cause!

Question 27

Who needs urgent admission following AKI?

Answer 27

1. Stage 3 kidney injury
2. No identifiable AKI cause
3. An underlying cause that requires urgent secondary care
4. Risk of urinary tract obstruction
5. Sepsis
6. Evidence of hypovolaemia and a need for intravenous fluid replacement and monitoring.
7. A deterioration in clinical condition or a need for observation
8. A complication of acute kidney injury requiring urgent secondary care management such as pulmonary oedema, uraemic encephalopathyor pericarditis, or severe hyperkalaemia.

Question 28

What is the prognosis for AKI?

Answer 28

The prognosis of AKI varies depending on clinical setting, the underlying cause, and any comorbidities

- There is also evidence that mortality increases with increasing stages of AKI
- AKI acquired in the community has a lower mortality rate than hospital acquired AKI
- People with chronic kidney disease preceding the episode of AKI there was a four- to five-fold increase in renal outcomes and mortality outcomes were doubled compared with people with AKI alone

Question 29

What are causes of acute deterioration in chronic kidney disease?

Answer 29

Systemic infection (urinary tract infection (UTI), chest infection, central line)
Drugs (diuretics, angiotensin-converting enzyme (ACE) inhibitors, aminoglycosides.)
Dehydration
Urinary tract obstruction or urinary retention (due to spinal cord compression or neurogenic bladder, or renal vein thrombosis)