Acute Kidney Injury and Urinary Tract Infections Flashcards
Define an acute kidney injury
A spectrum of disease associated with a sudden onset of renal parenchymal injury
What features of the kidneys make they at high risk of injury?
- High blood flow
- High metabolic demands
- Tubule cells can concentrate toxins
How does acute kidney injury differ from failure?
The word “Injury” rather than “failure” recognises the fact that recovery can occur
What are the consequences of an abrupt drop in kidney function?
- Abnormal GFR, tubular function and urine production
- A sudden inability to maintain fluid, acid-base, and electrolyte balance
- It may result in azotaemia
Describe the relationship between creatinine and GFR
- Not a straight line
- In the healthy state with normal renal function, you can have a really big drop in GFR and creatinine only goes up a little bit
- You have to lose 75% of GFR for creatinine to even go into the abnormal range
- Beyond that, small changes make a big difference!
What are the causes of an acute kidney injury?
Decreased renal blood flow
Toxins
Intrinsic renal diseases E.g. Leptospirosis, pyelonephritis
Systemic diseases
List some kidney toxins
Antibacterials (aminoglycosides)
NSAIDs
Ethylene glycol
Lilies (cat)
Grapes (dog)
Name the 4 phases of an acute kidney injury
Initiation phase
Extension phase
Maintenance phase
Recovery phase
Describe the initiation and extension phases of an AKI
Initiation - damage starts
Extension - ischemia, hypoxia, inflammation, ongoing cellular injury, cell death
Both of these phases may be clinically silent
Describe the maintenance phase of an AKI
Stabilisation of GRF
Typically see azotaemia, uraemia
Urine production is variable
Describe the recovery phase of an AKI
Azotaemia improves and the tubules undergo repair
Can be marked polyuria during this stage
If an acute kidney injury lasts longer than 7 days it is termed?
An acute kidney disease
If the kidney fails to return to normal after 90 days it is diagnosed as?
Chronic kidney disease
During recovery of the kidney, describe the two separate processes that occur
- Repair of kidney tissue. Renal function can return to normal, or repair could be maladaptive with inflammation, fibrosis, leading to permanent reduction in function (CKD).
- Activation of compensatory mechanisms in the remaining nephrons (ie, compensatory hypertrophy).
How can history be used to recognise an AKI?
Recent onset of anorexia, polydipsia, vomiting
May get CNS signs in ethylene glycol ingestion
Toxin exposure/ nephrotoxic drugs?
Ischaemic episode?
Vaccination status? – Leptospirosis
How can a physical exam be used to recognise an AKI - what are the clinical signs?
Uraemic breath
Hypothermia (unless infection)
+/- Kidney pain or enlargement
Tachycardia - dehydration, pain
Bradycardia - hyperkalaemia
Describe the blood test results seen in a patient with an AKI
- Azotaemia
- Increased phosphate
- Hyperkalaemia (if oliguric - can’t excrete)
- Calcium variable
Describe the urinalysis results seen in a patient with an AKI
Urine will probably be isosthenuric in AKI.
Can see glucosuria, haematuria.
Look at sediment for casts, WBCs, bacteria, crystals.
How might a CKD patient present in a way thats similar to an AKI
Present in “uraemic crisis” with acute decompensation of their azotaemia - be aware of this
Compare the main features of an AKI with CKD
AKI:
- Good BCS
- Acute onset of signs
- Possible history of toxin exposure
- Not anaemic
- Kidneys may be enlarged and painful
- Hyperkalaemia
- Good hair coat
CKD:
- Weight loss
- PUPD, poor appetite, GI signs
- Non-regenerative anaemia
- Kidneys small, firm and irregular
- Can seem well
- Normal or low potassium
- Poor hair coat