• Acute kidney injury (AKI) is an abrupt reduction in kidney function
• absolute increase in serum creatinine of either ≥26.4 µmol/L within 48 hr or
• ≥50% (1.5 x baseline) within 7 days or
• reduction in urine output documented as oliguria <0.5 mL/kg/hr for >6 hr
• E-Alert for AKI stages in Patient Management System

AKI stage 1

Creatinine

• Increase in creatinine ≥26.4 µmol/L within 48 hr or
• 1.5-2 fold increase from baseline within 7 days

Urine output

• <0.5 mL/kg/hr for >6 hr

AKI stage 2

Creatinine

• Increase in creatinine >2-3 fold from baseline within 7 days

Urine output

• <0.5 mL/kg/hr for >12 hr

AKI stage 3

Creatinine

• Increase in creatinine >3 fold or
• Serum creatinine >350 µmol/L with an acute rise of 1.5 fold within 7 days

Urine output

• <0.3 mL/kg/hr for 24 hr or anuria for 12 hr

Causes

• Pre-renal (perfusion)
• volume depletion
• hypotension, pump failure
• sepsis
• Renal (organ)
• established acute tubular necrosis - ischaemic or toxic
• glomerulonephritis/vasculitis
• tubulointerstitial nephritis
• Post-renal (obstructive)

Relevant clinical history

• Obtain previous U&E for evidence of pre-existing renal dysfunction
• Full medication history
• prescribed and non-prescribed drugs; iodinated contrast investigations
• History of urinary tract symptoms OR renal stone disease
• History suggestive of sepsis
• History of vascular disease

Fever, arthralgias, rashes

• Small vessel vasculitis
• granulomatosis with polyangiitis, microscopic polyangiitis
• SLE
• Anti-glomerular basement membrane antibody disease

Haemoptysis

• Small vessel vasculitis
• Anti-glomerular basement membrane antibody disease

Haemolysis, thrombocytopenia, Ischaemic events

• Haemolytic-uraemic syndrome
• Thrombotic thrombocytopaenic purpura

Hypercalcaemia, hyperuricaemia, bone pain, lytic lesions

• Multiple myeloma

Recent vascular intervention

• Cholesterol emboli syndrome
• ± livedo reticularis, hypocomplementaemia

Prolonged severe immobility, crush injuries

• Rhabdomyolysis
• raised serum creatinine, creatine kinase >10,000 U/L

Physiological observations and examination

ABCDE examination to include

• Any evidence of sepsis - start Sepsis Six Care Bundle. See Sepsis guideline
• Haemodynamic (including volume) assessment
• Signs of shock / hypoperfusion
• Reagent strip urinalysis - documented in medical records
• Palpation for enlarged bladder
• Evidence of vascular disease
• Signs suggestive of a less common cause include rashes (e.g. vasculitis) or altered neurology

Sepsis

• Use sequential organ failure assessment score (SOFA score)
  • qSOFA=quick Sofa score
• Suspected or confirmed infection
• Quick Sequential Organ Failure (qSOFA) score >2
  • RR >22 breaths/min
  • Systolic BP <100 mmHg
  • GCS ≤13

Complications of AKI

• Pulmonary oedema
• Hyperkalaemia - see Hyperkalaemia guideline
• Tachypnoea suggests fluid overload and/or acidosis
• Pericardial/pleural rub
• Neurological manifestations of uraemia
  • e.g. encephalopathy (exclude other causes of confusion/delirium)

Multiple organ failure

• Hypotension
  • mean arterial pressure (MAP) <65 mmHg despite initial fluid resuscitation up to 30 mL/kg, or
  • inotrope or vasopressor dependency
• Impaired gas transfer: hypoxaemia (PaO₂ <10 kPa) despite 40% oxygen
• Metabolic acidosis - compensated as well as uncompensated
• Pulmonary shadowing/oedema on chest X-ray
• Patient looks severely ill/exhausted/obtunded

Ultrasound

• If cause not identified, renal ultrasound scan within 24 hr of AKI recognition
• assess renal size/exclude obstruction
• If pyonephrosis [infected and obstructed kidney(s)] suspected, immediate ultrasound of the urinary tract
• perform within 6 hr of assessment

Indications for immediate referral

• Discuss with appropriate team immediately any patient with the following

Renal

• Complications of AKI refractory to medical management
• Creatinine >350 µmol/L or >3-fold rise in creatinine from known baseline (AKI Stage 3)
• Indications for dialysis
• Likely intrinsic renal disease / systemic vasculitis
• AKI (any stage) in a renal transplant patient
• If despite initial resuscitation, renal function declines (even if creatinine <300 µmol/L), refer patient within 48 hr of diagnosing AKI

Renal team or oncology

• Suspected tumour lysis syndrome (massively increased serum uric acid)

Urology and/or radiology

• Obstruction not relieved by catheter
• Pyonephrosis

Critical care

• Multi-organ failure
• Haemodynamic instability (follow NICE CG50) (Acutely ill adults in hospital: recognising and responding to deterioration) 

Sepsis

• See Sepsis guideline

Fluid balance

• Careful assessment of volume status including calculation of any fluid deficit
• Accurately chart fluid input and urine output (urinary catheter may be required)
• Fluid resuscitation with crystalloids to achieve appropriate physiological targets
  • systolic blood pressure >100 mmHg or MAP >65 (higher if normally hypertensive) and/or
  • resolution of tachycardia and/or
  • restoration of adequate urine output as per Fluid resuscitation guideline
• Insert CVP line if necessary for vasoactive drugs
• Once rehydrated, continue IV crystalloid to match urine output + 30 mL/hr plus continuing fluid losses

Oliguria

• In patients who remain oliguric, carry out careful reassessment to avoid fluid overload
• If patient is fluid overloaded (i.e. pulmonary oedema with oliguria), give furosemide 250 mg in 25 mL by IV infusion over 2 hr using infusion pump or syringe driver
  • smaller doses of furosemide 40mg to 80mg daily may be sufficient for mild overload
  • do not use furosemide unless evidence of fluid overload
  • restrict fluid to 1-1.5 L daily and monitor response
  • if no response and fluid overloaded, contact renal team urgently to consider dialysis
• Recheck U&E daily to assess changes in renal function
• Do not use dopamine or mannitol

Urinary tract obstruction

• Undertake nephrostomy or stenting as soon as possible and within 12 hr of diagnosis

Drugs

• Discontinue/avoid nephrotoxins
  • e.g. NSAIDs/ACE inhibitors/angiotensin-II receptor antagonists
• Stop metformin/sulphonylurea/SGLT-2 inhibitor drugs
  • may accumulate in AKI or have increased risk of adverse effects
• Adjust dose of any drugs given in renal failure. Consult BNF or renal drug handbook
• Consider appropriateness of restarting drugs following resolution of AKI

Renal replacement therapy

• If there is evidence of the indications below, refer to renal team for possible haemodialysis or continuous renal replacement therapy

Biochemical indications

• Refractory hyperkalaemia > 6.5 mmol/l
• Refractory metabolic acidosis pH < 7.15
• Tumour lysis syndrome with hyperuricaemia and hyperphosphataemia
• Urea cycle defects, and organic acidurias resulting in hyperammonaemia, methylmalonic acidaemia

Clinical indications

• Urine output < 0.3 ml/kg for 24 h or absolute anuria for 12 h
• AKI with multiple organ failure
• Urine output failure with refractory volume overload
• End organ involvement: pericarditis, encephalopathy, neuropathy, myopathy, uraemic bleeding
• Creation of intravascular space for plasma and other blood product infusions and nutrition
• Severe poisoning or drug overdose with TOXBASE advice

• Discuss with renal team
• Refer to dietician for support

• Daily weight and fluid balance
• Daily U&E
• Monitoring of underlying cause
• Daily review of medications and need for dose adjustments

• If renal function remains abnormal despite treatment and eGFR <30 mL/min, arrange outpatient review by renal team
• U&E check in community within 6 weeks with GP team or, if eGFR <30, within 2 weeks
• Patient medication advice leaflet available for patients with CKD, hypertension and cardiac failure