Acute Kidney Injury (AKI) Flashcards
Define Acute Kidney Injury (AKI).
An abrupt (over hours to days) sustained rise in serum urea and creatinine due to a rapid decline in GFR, leading to a failure to maintain fluid, electrolyte and acid-base homeostasis.
It is usually but not always reversible or self-limiting.
Simple terms: Acute drop in kidney function.
What is the affect of AKI on creatinine and urine output?
- Creatinine is raised.
- Urine output is reduced.
What is a normal GFR?
60ml/min/1.73m2 +
What is the NICE criteria for 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
What are the 2 systems used for AKI classification?
- RIFLE
- KDIGO
Describe the RIFLE classification system for AKI.
Criteria:
* Risk
* Injury
* Failure
* Loss
* End-stage renal disease
What are the stages of the KDIGO system used for AKI?
1 - 150-200% increase in creatinine. less than 0.5ml/kg/hr for 6 hrs
2 - 200-300% increase in creatinine, less than 0.5mg/kg/hr for 12 hours
3 - less than 0.3ml/kg/hr
Give 5 risk factors for AKI.
- Increasing age (>65 YO)
- CKD.
- HF.
- Diabetes mellitus.
- Nephrotoxic drugs e.g. NSAIDs and ACEi.
- Contrast dyes
- Infection
- Dehydration
- Peripheral vascular disease
- Liver disease
- Past history of AKI
- Hypovolaemia
Give 3 pre-renal cause of AKI.
- Hypotension (shock)
- Heart failure
- Nephrotoxic drugs - NSAIDs, ACEi
- Bleeding
- Dehydration or haemorrhage
- Sepsis
Give 5 renal causes of AKI.
- Nephrotoxic drugs - NSAIDs, ACEi
- Vasculitis.
- Autoimmune.
- Acute tubular necrosis.
- Glomerulonephritis - nephritic / nephrotic syndromes
- Interstitial nephritis.
Give 3 post renal causes of AKI.
- Kidney stones
- Masses such as cancer in the abdomen or pelvis
- Ureter or uretral strictures
- Enlarged prostate or prostate cancer
- Benign prostate hyperplasia
- Urinary tract obstruction at ureter, bladder or prostate
Clinical presentation of AKI.
Often asymptomatic.
Pre-renal – hypotension (D&V, syncope, pre-syncope), signs of liver or heart failure (oedema)
Renal – infection, signs of underlying disease (vasculitis, glomerulonephritis, DM)
Post-renal – LUTS (BPH)
Universal:
- Oliguria (<0.5 mL/kg/hr >6hrs)
- High creatinine
- Hyperkalaemia – arrhythmias, muscle weakness
- Uraemia – N&V, weakness, pericarditis (if severe), platelet dysfunction (bleeding)
- Hypocalaemia / hyperphosphataemia (vitamin D def)
- ?Trauma – signs of direct injury
What investigations might you do to determine whether someone has AKI?
Establish the cause.
- Urinalysis
- Urine dipstick testing for blood, protein, leucocytes, nitrites and glucose - Ultrasound
- CT-KUB (kidney, ureter, bladder)
- Bloods
- U&E (eGFR)
- Creatinine
Management of AKI.
- Treat underlying cause
Pre-renal:
- Volume depletion with fluids
- Treat sepsis with antibiotics
Renal:
- Referral to nephrology
Post-renal:
- Relieve obstruction e.g. catheterise
- Consider a CT KUB - Stop nephrotoxic drugs
- NSAIDs, ACEi, Gentamycin, amphotericin - Optimise fluid balance
- Diet: Na+/K+ retriction and supply vitamin D
- Renal replacement therapy (RRT)
What drugs should be stopped in AKI?
NSAIDs, ACEi
