Acute Kidney Injury (AKI)

What is acute renal injury

a sudden decline in renal excretory function over hours or days that can result in failure to maintain fluid, electrolyte, and acid-base balance

How do you diagnose acute kidney disease?

acute increase in serum creatinine and a reduction in urine output (oliguria)

risk factors for acute kidney injury

aged 65 years or over.

history of AKI or urological obstruction.

history of CKD, heart failure, liver disease, or diabetes mellitus

taking NSAIDS, ACEi

sex: female

ethnicity: black

causes of pre renal AKI

• volume depletion

• reduced ECV

• renal hypoperfusion

• renal artery stenosis

• altered renal autoregulation by drugs

What is Prerenal Acute Kidney Injury?

Results from decreased renal perfusion, causing impaired oxygenation of renal tissue

reverses rapidly once renal perfusion is restored

Not associated with structural renal injury

Causes of renal AKI

• ischaemic injury

• nephrotoxic injury

• immune-mediated injury

• vascular disease

** structural damage to the kidneys!

causes of post-renal AKI

partial or complete obstruction of the urinary collecting system

How does Drug-induced prerenal acute kidney injury happen?

what can cause Acute Tubular Necrosis?

result of ischemic or nephrotoxic injury or a combination of both
• Trauma
• vascular and cardiac surgery
• severe burns
• pancreatitis
• sepsis
• chronic liver disease

** uncomplicated ATN is recovery over 2 to 3 weeks

what part of the tubule is vulnerable to hypoxic injury and why?

S3 segment of proximal tubule cells and distal
medullary thick ascending limb

• Countercurrent oxygen exchange leading to a progressive fall in PO2 from cortex to medulla

• High tubular energy requirements for ion pumps

What happens in Acute Tubular Necrosis?

Tubular Cells death:

• Loss of brush border
• Disruption of actin cytoskeleton
• Abnormal translocation Na + K + -ATPase
• Loss of cellular polarity

Cast Obstruction
Back leak of filtered tubular fluid

Endogenous nephrotoxins 

Exogenous nephrotoxins 

what caused Rhabdomyolysis and why does it cause kidney injury?

Due to muscle injury - release of myoglobin

Myoglobin filtered at glomerulus and toxic to tubule cells

Can also cause obstruction

symptom of Rhabdomyolysis

It causes red-brown colored urine (urine dipstick positive for heme but negative
for RBCs)

prerenal vs renal vs postrenal

Primary prevention of AKI

manage/ prevent:

hypovolaemia

hypotension

nephrotoxic drugs/ nephtoxic contrast media

sepsis

Clinical evaluation of AKI

history: look out for risk factors

Physical examination: evaluation of fluid status, signs for acute and chronic heart failure, infection and sepsis

Lab: urine output and serum creatinine, urea, electrolytes (particularly potassium), Urine analysis and microscopic examination

Imaging tests: ultrasound

AKI complications

(1)Hyperkalaemia.
(2) Other electrolyte imbalances: hyperphosphataemia, hyponatraemia, hypermagnesaemia, hypocalcaemia.
(3) Metabolic acidosis.
(4) Fluid overload (peripheral and pulmonary oedema); heart failure; lung injury; liver injury.
(5) Uraemia.
(6) Chronic kidney disease and kidney failure

Treatment of AKI

Treating any underlying cause

Temporarily stopping or reducing specific medications

Fluid and electrolyte management

Supportive measures: glycaemic control, BP control and nutrition

If urinary tract obstruction: urological intervention to re-establish urine flow

Renal replacement therapy

What patients wit AKI need renal replacement therapy?

No response to treatment with:

• Hyperkalaemia

• Metabolic acidosis

• Fluid overload

• Pulmonary oedema

• Symptoms of uraemia (pericarditis or encephalopathy)