Acute Kidney Injury (AKI)

Exam Cram

• Acute Kidney Injury (AKI) describes an acute impairment to kidney physiology and is associated with longer hospital stay and mortality

• AKI has a range of causes: pre-renal (hypovolaemia), renal (ATN) and post renal (obstructive e.g. BPH)

• Diagnosis: acute significant rise in creatinine

• Management: as per underlying cause [commonly fluids or furosemide]

Outline

Background

• Affects at least 1% of patients on admission & 30% ICU admissions

• Key is early recognition to prevent deterioration

Assessment

History

• Asymptomatic 

• Vague fatigue, reduced exercise tolerance, shortness of breath

• Symptoms as per underlying cause- sepsis, NSAIDs

Examination

• May be normal

• Hypertension (observation) 

Investigations

• Raised creatinine

• Urine dip: protein, blood

• Albumin: creatinine ratio

• Imaging: renal US/ CT KUB / CTAP with contrast- rule out obstruction

Diagnosis

Diagnostic criteria: KDIGO 2012 (1/3)

1. Creatinine rise by 26umol in 48hrs

2. Creatinine increase by 1.5 from baseline in 7d

3. Urine volume < 0.5mk/kg/hr for 6hrs 

Classification (aetiology):

• Pre-renal: shock

  • Increased losses: 

    • Gastroenteritis , Ulcerative Colitis , DKA

    • Bleeding: e.g. GI, trauma

  • Reduced input: dehydration, neglect, burns

  • Cardiogenic shock: Myocardial Infarction , CHF , Aortic Dissection 

  • Immunogenic shock: Sepsis , Anaphylaxis 

  • Renal arterial vasoconstriction: Renal Artery Stenosis , NSAIDs, Hepatorenal Syndrome (HRS), [ACEi- efferent dilatation]

• Renal

  • Acute Tubular Necrosis 

  • Acute Interstitial Nephritis 

  • Glomerulonephritis

  • Intratubular obstruction: Multiple Myeloma , Tumour Lysis Syndrome , Haemolytic Anaemia (HA)  , ethylene glycol

• Post renal: obstructive

  • Benign Prostatic Hypertrophy 

  • Urinary Stones 

  • Renal & Bladder Cancer 

  • Intrabdominal malignancy: ovarian, endometrial, prostate

  • Hydronephrosis, retroperitoneal fibrosis, pregnancy, pelvic prolapse

Management

Acute

• As per underlying cause

Long Term

• Repeat urea, creatinine & electrolytes

• Albumin: Cr ratio

• Consider Renal follow up

Renal Reg Notes

References

1. https://www.kidney.org/kidney-topics/acute-kidney-injury-aki#:~:text=Many%20people%20get%20AKI%20when,substances%20that%20you%20may%20consume

2. https://www.kidneyresearchuk.org/conditions-symptoms/acute-kidney-injury/

3. Goyal A, Daneshpajouhnejad P, Hashmi MF, et al. Acute Kidney Injury. [Updated 2023 Nov 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441896/

Resources

• National Kidney Foundation

Written in 2025