Acute Kidney Injury Flashcards
(32 cards)
What is acute kidney injury (AKI)?
Akidney injury (AKI) is a term covering a spectrum of injury to the kidneys which can result from a number of causes. It is a clinical syndrome rather than a biochemical diagnosis.
Differentiate between pre-renal, renal and post-renal causes of AKI
Pre-renal (most common): due to reduced perfusion of the kidneys and leading to a decreased glomerular filtration rate (GFR). It is usually reversible with appropriate early treatment
Intrinsic renal: a consequence of structural damage to the kidney, for example, tubules, glomeruli, interstitium, and intrarenal blood vessels. It may result from persistent pre-renal or post-renal causes damaging renal cells.
Post-renal (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.
Give examples of pre-renal causes of AKI
Hypovolaemia (e.g. inability to maintain hydration without help from others, haemorrhage, gastrointestinal losses, renal losses, burns).
Reduced cardiac output (e.g. cardiac failure, liver failure, sepsis, drugs).
Drugs that reduce blood pressure, circulating volume or renal blood flow (e.g. ACE inhibitors, ARBs, NSAIDs, loop diuretics).
Give examples of renal causes of AKI
Toxins and drugs (for example antibiotics, contrast, chemotherapy).
Vascular (e.g. vasculitis, thrombosis, athero/thromboembolism, dissection).
Glomerular (e.g. glomerulonephritis).
Tubular (e.g. acute tubular necrosis, rhabdomyolysis, myeloma).
Interstitial (e.g. interstitial nephritis, lymphoma infiltration).
Give examples of post-renal causes of AKI
Obstruction (e.g. renal stones, blocked catheter, enlarged prostate, genitourinary tract tumours/masses, neurogenic bladder).
What are the risk factors for AKI?
- People aged 65 years or over
- A history of acute kidney injury
- Chronic kidney disease
- Symptoms or history of urological obstruction or conditions which may lead to obstruction
- Chronic conditions such as heart failure, liver disease and diabetes mellitus
- Use of a contrast medium such as during CT scans
- Neurological or cognitive impairment or disability (which may limit fluid intake because of reliance on a carer)
- Sepsis
- Hypovolaemia
- Oliguria
- Nephrotoxic drug use within the last week
Give examples of nephrotoxic drugs
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Angiotensin-converting enzyme (ACE) inhibitors
- Angiotensin II receptor antagonists (ARBs)
- Diuretics
What are the signs of AKI?
- Hypotension
- Volume overload (e.g. crackles, tachypnoea)
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What are the symptoms of AKI?
- Nausea and vomiting, or diarrhoea, evidence of dehydration
- Reduced urine output or changes to urine colour
- Confusion, fatigue and drowsiness
What investigations should be ordered for AKI?
- Basic metabolic panel (including urea and creatinine)
- Serum potassium
- FBC
- CRP
- Blood culture
- Urinanlysis
- Urine culture
- Urine output monitoring
- CXR
- ECG
According to NICE, what criteria must be met to diagnose AKI?
- Rise in creatinine of ≥ 25 micromol/L in 48 hours
- Rise in creatinine of ≥ 50% in 7 days
- Urine output of < 0.5ml/kg/hour for > 6 hours
Why investigate urea and creatinine?
AKI is diagnosed based on an acute rise in serum creatinine and/or a sustained reduction in urine output.
- A rise in serum creatinine of 26 micromol/L or greater within 48 hours
- A 50% or greater rise in serum creatinine (more than 1.5 times baseline) known or presumed to have occurred within the past 7 days
- A fall in urine output to less than 0.5 mL/kg/hour for more than 6 hours (if it is possible to measure this, for example, if the person has a catheter)
Why investigate serum potassium?
Ensure close monitoring of serum potassium.
Hyperkalaemia is a common complication of AKI.
Why investigate FBC?
May show anaemia, leukocytosis and/ or thrombocytopenia.
Why investigate CRP?
Request in all patients.
Elevated in infection and also in vasculitis.
Why investigate using blood culture?
Request if infection is suspected.
Sepsis is a common cause of AKI.
Why investigate using urinanalysis?
Perform urine dipstick testing for specific gravity, blood, protein, leucocytes, nitrites and glucose as soon as AKI is suspected or diagnosed.
Why investigate urine culture?
Send urine culture if clinical features of urinary tract infection are present and/or urinalysis is positive for blood, protein, leukocytes, or nitrites.
May show bacterial growth with antibiotic sensitivity.
Why investigate via measuring urine output?
Start urine output monitoring in any patient diagnosed with AKI (hourly if catheterised, 4-hourly if not).
Confirm a diagnosis of AKI if urine output <0.5 ml/kg/hour for at least 6 consecutive hours (at least 8 hours in children/young people).
Why investigate using CXR?
Request a chest x-ray. It may demonstrate signs of:
- Infection
- Pulmonary oedema
- Haemorrhage (e.g., ANCA-associated vasculitis, Goodpasture syndrome [pulmonary haemorrhage, rapidly progressive glomerulonephritis, and anti-glomerular basement membrane antibodies])
- Cardiomegaly
Why investigate using ECG?
An ECG is important to assess for hyperkalaemia.
Hyperkalaemia is a common complication of AKI.
What changes can be seen on an ECG with hyperkalaemia?
ECG changes associated with hyperkalaemia:
- Peaked T waves
- Increased PR interval
- Widened QRS
- Atrial arrest
- Deterioration to a sine wave pattern
When should renal ultrasound be used to diagnose AKI?
If pyonephrosis (an infected/obstructed renal tract) is suspected, ensure the patient has an ultrasound - and if indicated a nephrostomy - within 6 hours due to the risk of septic shock.
Renal tract ultrasound is not routinely required. Only request it if no obvious cause for the AKI can be found or if obstruction, pyelonephritis, or pyonephrosis is suspected.
