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Acute kidney injury

Definition
AKI is a sudden decrease in kidney function resulting from structural or functional injury that is characterized by decreased GFR, increased serum creatinine, and oliguria.
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Pathophysiology
AKI has multiple possible causes, including renal hypoperfusion, intrinsic renal dysfunction (glomerulonephritis, vasculitis, tubular necrosis, interstitial nephritis), or obstruction to the emptying of the kidneys (post-renal AKI).
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Epidemiology
The incidence of AKI in the US is estimated at 179-317 cases per 100,000 person-years.
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Disease course
Hypoperfusion of the kidneys with resultant ischemic injury represents the most important group of etiologies, mediating AKI through cellular injury caused by a mismatch between oxygen and nutrient delivery to the nephrons.
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Prognosis and risk of recurrence
Approximately 40% of patients with AKI do not recover renal function by hospital discharge. In this group of patients, AKI is associated with 1-year age-adjusted mortality of approximately 60%, compared to approximately 10% in patients who recovered renal function within 7 days.
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Key sources
The following summarized guidelines for the evaluation and management of acute kidney injury are prepared by our editorial team based on guidelines from the Enhanced Recovery After Surgery Society (ERASS/POQI 2023), the American College of Radiology (ACR 2023; 2021), the Canadian Association of Radiologists (CAR 2022), the American Society for Extracorporeal Technology (AmSECT/STS/SCA 2022), the European Society of Cardiology (ESC 2021), the National Institutes of Health (NIH 2021), the Acute Disease Quality Initiative (ADQI 2020; 2017), the United Kingdom Kidney Association (UKKA 2019), the Japanese Society of Blood Purification in Critical Care (JSBPCC/JSPN/JSDT/JSICM/JSN 2018), the European Society for Vascular Surgery (ESVS 2017), the European Renal Best Practice Foundation (ERBP 2012), the Kidney Disease: Improving Global Outcomes Foundation (KDIGO 2012), the American Society for Parenteral and Enteral Nutrition (ASPEN 2010), and the European Society of Intensive Care Medicine (ESICM 2010).
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Guidelines

1.Screening and diagnosis

Diagnostic criteria: as per ERBP 2012 guidelines, diagnose and stage the severity of AKI as follows (meeting any of the criteria):
Situation
Guidance
Stage 1
Serum creatinine increase 1.5-1.9 times baseline
Serum creatinine increase > 0.3 mg/dL (26.5 mcmol/L)
Urinary output < 0.5 mL/kg/hour during a 6 hour block
Stage 2
Serum creatinine increase 2.0-2.9 times baseline
Urinary output < 0.5 mL/kg/hour during two 6 hour block
Stage 3
Serum creatinine increase > 3 times baseline
Serum creatinine increase > 4.0 mg/dL (353 mcmol/L)
Initiation of RRT
Urinary output < 0.3 mL/kg/hour during > 24 hours
Anuria for > 12 hours
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  • Definitions

  • Differential diagnosis

2.Classification and risk stratification

Risk assessment: as per ADQI 2020 guidelines, avoid using biomarkers of acute damage before a kidney injury for the assessment of AKI risk.
D
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3.Diagnostic investigations

Baseline renal function testing: as per JSN 2018 guidelines, assess the baseline renal function using multiple methods whenever possible.
B

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  • Urinalysis

  • Renal ultrasound

  • Novel biomarkers

  • Evaluation for etiology

4.Medical management

General principles: as per UKKA 2019 guidelines, obtain relevant assessment in patients at risk of AKI exposed to a significant renal insult, to ensure that exposure is limited and further insults are avoided or minimized.
B
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  • Fluid resuscitation

  • Vasopressors

  • Management of hyperglycemia

  • Therapies with no evidence for benefit

5.Inpatient care

Renal function monitoring, patients at risk for acute kidney injury, UKKA: obtain close monitoring for AKI in adult inpatients deemed at high risk of AKI, particularly if there has been a new exposure. Monitor urine output and measure serum creatinine daily until at least 48 hours after the period of increased risk has elapsed.
B
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  • Renal function monitoring (patients with AKI)

  • Hemodynamic monitoring

6.Nonpharmacologic interventions

Nutritional support: as per UKKA 2019 guidelines, refer patients with AKI receiving RRT to a dietitian for individual assessment.
B

7.Therapeutic procedures

Renal replacement therapy, indications, UKKA: consider initiating acute RRT in patients with progressive or severe AKI unless a decision has been made not to escalate therapy.
B
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  • RRT (choice of modality)

  • RRT (dosing)

  • RRT (insertion of dialysis catheter)

  • RRT (periprocedural anticoagulation)

  • RRT (technical considerations)

  • RRT (evaluation of fistula malfunction)

  • RRT (management of fistula malfunction)

8.Specific circumstances

Pediatric patients, diagnosis and evaluation: consider using the KDIGO diagnostic criteria for AKI to predict the survival outcomes in pediatric patients ≥ 3 months of age.
C
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  • Pediatric patients (RRT)

  • Pediatric patients (monitoring)

  • Patients with COVID-19-associated AKI (evaluation)

  • Patients with COVID-19-associated AKI (general principles of management)

  • Patients with COVID-19-associated AKI (hemodynamic support)

  • Patients with COVID-19-associated AKI (RRT)

9.Preventative measures

Prevention of acute kidney injury in intensive care unit, fluid therapy: initiate controlled fluid resuscitation in true or suspected volume depletion.
B
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  • Prevention of AKI in ICU (vasopressors and inotropes)

  • Prevention of AKI in ICU (vasodilators)

  • Prevention of AKI in ICU (nutritional support)

  • Prevention of AKI in ICU (other measures)

  • Prevention of contrast-induced nephropathy (risk assessment)

  • Prevention of contrast-induced nephropathy (restriction of contrast medium use)

  • Prevention of contrast-induced nephropathy (discontinuation of medications)

  • Prevention of contrast-induced nephropathy (IV and oral fluids)

  • Prevention of contrast-induced nephropathy (N-acetylcysteine)

  • Prevention of contrast-induced nephropathy (other agents)

  • Prevention of contrast-induced nephropathy (RRT)

  • Prevention of contrast-induced nephropathy (serial creatinine assessment)

  • Prevention of postoperative AKI

  • Prevention of rhabdomyolysis-induced AKI

  • Prevention of amphotericin B-induced nephrotoxicity

  • Prevention of aminoglycoside-induced nephrotoxicity

  • Prevention of cardiac surgery-associated AKI (preoperative care)

  • Prevention of cardiac surgery-associated AKI (intravascular volume maintenance)

  • Prevention of cardiac surgery-associated AKI (pharmacologic strategies)

  • Prevention of cardiac surgery-associated AKI (cardiopulmonary bypass strategies)

  • Prevention of cardiac surgery-associated AKI (minimally invasive extracorporeal circulation)

  • Prevention of cardiac surgery-associated AKI (postoperative care)

  • Measures with no evidence for benefit

10.Follow-up and surveillance

Discharge from hospital: include a record in the discharge summary regarding AKI detected whilst in hospital, its maximum stage, etiology, the need for renal support (temporary/ongoing), and discharge renal function, if dialysis-independent.
B
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  • Follow-up