What is the normal function of the kidneys?
Excretory functions: • Remove waste products • Remove excess fluid • Regulate acid-base balance • Regulate electrolyte levels
Secretory functions
• Renin -> regulate BP
• EPO -> regulate RBC production
• Active vitamin D -> regulate calcium uptake
What is an AKI?
A clinical syndrome characterised by a rapid reduction in renal excretory function due to several different causes
What are the symptoms of an AKI?
Sometimes asymptomatic
- Nausea, vomiting and diarrhoea
- Reduced urine output or changes to urine colour
- Confusion, fatigue and drowsiness
What are the risk factors for an AKI?
- > 65yrs
- Hx AKI
- CKD (eGFR<60)
- Symptoms or Hx or urological obstruction
- Chronic conditions (HF, Liver disease, DM)
- Neurological or cognitive impairment
- Sepsis
- Hypovolaemia
- Oliguria (urine output less than 0.5mL/kg/hour)
- Nephrotoxic drug use within last week (especially if hypovolaemic)
- Exposure to iodinated contrast agents
What are nephrotoxic medications?
- NSAIDs
- Aminoglycosides
- ACE-i
- ARBs
- Diuretics
What signs of autoimmune disease relevant to AKI?
o Fever o Rash o New arthritis o Nasal crusting/bleeding o Haemoptysis o New deafness o Mouth ulcers o Alopecia o Iritis/ episcleritis o Mononeuritis multiplex or neuropathy
What are you looking for when doing a volume status examination?
o Drowsy, yawning and thirsty
o Core temperature
o Peripheral perfusion (capillary refill)
o HR
o BP (lying and standing)
o JVP
o Fluid intake and losses
o Moistness of mucous membranes, skin turgor
o Changes in urination pattern
o Peripheral oedema and pulmonary crackles
What signs are specific for renovascular disease?
o Audible abdominal bruits
o Impalpable peripheral pulses
What signs suggest an obstructive cause of AKI?
o Poor stream o Hesitancy o Frequency o Nocturia o PV bleeding o Stones o Colicky pain o Palpable bladder
How is an AKI detected?
- Rise in serum creatinine of 26 micromol/litre ≥ within 48 hours
- 50% ≥ rise in serum creatinine (1.5X baseline) known or presumed to have occurred within the past 7 days
- A fall in urine output <0.5ml/kg/hour for > 6 hours in adults and 8 hours in children
- > 25% fall in eGFR in children and young people in the past 7 days
What is KGIO stage 1 for AKI?
SCr
- Increase ≥ 26 micromol/litre within 48 hours
OR
- Increase ≥ 1.5-1.9X compared to baseline
Urine output
- < 0.5ml/kg/hr for >6 hours
What is KGIO stage 2 for AKI?
SCr
- Increase ≥ 2-2.9X compared to baseline
Urine output
- <0.5ml/kg/hr for >12 hours
What is KGIO stage 3 for AKI?
SCr - Increase ≥3X compared to baseline OR - Increase ≥ 354 micromol/L OR - Commenced on RRT irrespective of stage
Urine output
- <0.3ml/kg/hr for >24 hours
OR
- Anuria for 12 hours
How do you compare serum creatinine to a baseline?
- Lowest creatinine value within 7 days
- Look at older results and use lowest or mean creatinine value from between 7 days – 1 year
- If no baseline available, repeat creatinine measurement after 48-72 hours
What can raise baseline creatinine?
- CKD progression
- Trimethoprim treatment
- Recently completed pregnancy
What is the most common cause of AKI?
Pre-renal
- Dehydration
- Sepsis
What are the pre-renal causes of AKI?
Reduced renal perfusion
- Dehydration
- Sepsis
- Hypotension
- Shock
- Hepatorenal syndrome
- Severe HF
- Intra-abdominal hypertension/compartment syndrome
What are the renal causes of AKI?
Intrinsic damage to glomeruli, renal tubules or interstitium of the kidneys
- NSAIDs
- ACE-i
- ARBs
- Gentamicin
- GN/vasculitis
- Contrast
- Interstitial nephritis
- Myeloma
- Rhabdomyolysis
- Acute tubular necrosis
- Glomerulonephritis
What are the post-renal causes of AKI?
Obstruction
- Prostate enlargement
- Kidney or ureteric stones
- Pelvic cancer
- External compression of ureter
