Acute Kidney Injury (AKI) Flashcards
What is acute kidney injury (AKI)?
AKI is a sudden, potentially reversible inability of the kidney to maintain normal body chemistry and fluid balance. It is usually accompanied by oliguria (urine output <0.5mL/kg/h or <1mL/kg/h in a neonate). However, polyuric AKI can also occur.
What are the 3 different types of AKI?
Causes are pre-renal, renal (including acute-on-chronic kidney disease), and post-renal.
A patient may have more than one cause for their AKI.
Give examples of pre-renal causes of AKI
Hypovolaemia: GI losses, burns, third-space losses (post-operative, sepsis, and nephrotic syndrome) and excess renal losses (renal tubular disorders).
Peripheral vasodilatation: sepsis.
Circulatory failure: congestive cardiac failure, pericarditis and cardiac tamponade.
Bilateral renal arterial or venous thrombosis.
Drugs: diuretics, ACE inhibitors and NSAIDs.
Hepato-renal syndrome.
Give examples of renal causes of AKI
Arterial: embolic, arteritis and HUS.
Venous: renal venous thrombosis.
Glomerular: acute GN.
Tubular: established ATN due to prolonged pre-renal AKI, ischaemia, toxins, drugs and obstructive (crystals).
Interstitial: tubulo-interstitial nephritis and pyelonephritis.
Acute-on-chronic: decompensation of CKD due to intercurrent illness.
Give examples of post-renal causes of AKI
Obstruction in a solitary kidney.
Bilateral ureteric obstruction.
Urethral obstruction.
Neuropathic bladder.
What are the clinical features of dehydration?
Tachycardia, cool hands, feet, and nose (>2°C core–peripheral temperature gap), prolonged CRT, low BP (late sign), dry mucous membranes and sunken eyes.
What are the clinical features of intravascular fluid overload?
Tachycardia, gallop rhythm, raised JVP and BP and palpable liver.
What investigations should be ordered for AKI?
- Ultrasound scan of kidneys
- Urine biochemistry
- Urinanalysis
- FBC
- U&E
- Coagulation screen
- Blood culture and CRP
- CXR if respiratory or cardiac signs
- Renal biopsy
Why investigating using ultrasound?
Urgent USS to look for:
- Obstruction, signs of CKD (small or cystic kidneys)
- In most cases of AKI, the kidneys are enlarged and echo-bright
- Doppler studies if an abnormality of renal blood flow is suspected
Why investigate using urine biochemistry?
Urine biochemistry is useful in distinguishing between pre-renal AKI and established ATN.
Urinary Na+ (UNa) <10mmol/L (<20 in neonates), fractional excretion of sodium (FeNa) <1% (<2.5% in neonates) and urine osmolality >500mOsm/kg (>400 in neonates) suggest pre-renal AKI.
Why investigate using renal biopsy?
Renal biopsy is indicated as soon as possible when:
- Renal function is deteriorating and the aetiology is not certain
- Nephritic/nephrotic presentation
What AKI presentations would need emergency treatment?
The patient may require transfer to a paediatric nephrology centre if dialysis looks likely or there is uncertainty about the diagnosis. The following may need emergency management:
- • Hyperkalaemia (K+ >6.5mmol/L)
- • Metabolic acidosis
- • Hypertension
- • Shock
- • Fluid overload
- • Hypocalcaemia
- • Hypo-/hypernatraemia
What are the indications for dialysis?
- Oligo-anuria with no response to furosemide
- Hyperkalaemia >6.5mmol/L with T-wave changes on ECG
- Severe fluid overload with pulmonary oedema
- Urea >40mmol/L (consider >30mmol/L in a neonate)
- Severe hypo- or hypernatraemia or acidosis
- Multisystem failure
- Anticipation of prolonged oliguria
What are the acute dialysis methods?
- Peritoneal dialysis
- Haemodialysis
- Haemofiltration
