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
How is an AKI managed?
Specific treatment to eliminate the cause
Supportive treatment
Describe some possible specific treatments for an AKI
- Induce vomiting if recent toxin ingestion (antifreeze, lilies)
- Signs of AKI occur after 24-72h. Often present with vomiting, salivation, or neurological signs (tremors, seizures, ataxia).
- Give ABs if leptospirosis is suspected (or until pyelonephritis is ruled out)
Describe supportive treatment for an AKI
Initial IVFT- based on degree of hydration
What are the goals for fluid resuscitation in an AKI?
- Optimize intravascular circulating volume
- Increase cardiac output and perfusion pressure
- Improve renal blood flow, renal oxygen supply, and GFR
Should you use aggressive fluid therapy in an AKI? Why?
There is no evidence that aggressive IVFT (forced diuresis) can increase the rate of excretion of uraemic solutes above that achieved by restoration of normal perfusion
Don’t flush the kidneys
What are the possible consequences of IVFT and fluid overload?
Central nervous system – oedema
Lungs - oedema
Heart, liver gastrointestinal tract
What is oliguria?
Urine flow less than 2ml/Kg/hour - if hydrated and well perfused
Which drugs can be used to increase urine output?
Furosemide
- Increases urine output but does not improve GFR or outcome
- Allows you to carry on with IVFT
What consequences should you look out for when treating oliguria/anuria
- Polyuria: once the animal recovers from oliguria or anuria
- Acid-base/electrolyte abnormalities: Metabolic acidosis frequently occurs, Bicarbonate treatment can be risky
- Hyperkalaemia
Which drug is used in a vomiting patient?
Maropitant
How can you treat hypertension?
Exacerbated by overhydration
Reduce ivft, give diuretics
If persistent- can use antihypertensives but most are oral
You’ve just done a cruciate repair in a 10 year old dog- under anaesthesia the dog became hypotensive for several minutes. On recovery, is it safe to give a NSAID?
Risk of AKI
Not safe
In which patients are UTI most commonly seen?
Females>males
Dogs>cats
Define a UTI
Adherence, multiplication and persistence of an infectious agent within the urinary system
Define a bacteriuria
Bacteria in the urine
Define a pyuria
white blood cells in the urine.
Why are bacteria UTIs more common in females?
shorter, wider urethra
What is sporadic bacteria cystitis?
- Common in dogs
- Diagnosed when there is a bacterial infection with compatible clinical signs.
- Occurs in otherwise healthy female or neutered male dogs. Rare in intact male dogs (suspect prostatitis in these!)
What is recurrent bacterial cystitis?
Diagnosed when there are 3 or more episodes of bacterial cystitis in the previous 12 months
Define pyelonephritis
Infection of the renal parenchyma
What is bacterial prostatitis
Intact male dogs with UTIs should be assumed to have prostatic infection
What is a subclinical bacteriuria?
The presence of bacteria in urine as determined by positive bacterial culture from a properly collected urine specimen, in the absence of clinical signs.
Common especially in elderly animals, also diabetics, those recovering from disc surgery, others.
What are the clinical signs of cystitis?
Dysuria, pollakiuria, haematuria or urinary incontinence
What are the clinical signs of a pyelonephritis?
Abdominal pain, AKI, or septicaemia
May also have PUPD
How are UTIs diagnosed?
Urinalysis - beware dipsticks.
Urine sediment examination
- Significant numbers of WBCs (>5 per hpf)
- Bacteria
URINE CULTURE
How is sporadic bacterial cystitis treated?
Antibiotics for 3-5 days
NSAIDs can be used as well
Amoxicillin, cephalexin or trimethoprim.
Don’t use fluoroquinolones or extended release cephalosporins
How is recurrent bacterial cystitis treated?
Treat for 3-5 days but consider longer (7-14 days) if factors that may impair response are suspected to be present
List some predisposing causes for recurrent bacterial cystitis
Endocrinopathy
Kidney disease
Obesity
Abnormal vulval conformation
Congenital abnormalities
Prostatic disease
Bladder tumour
Urolithiasis
Immunosuppressive therapy
Urinary incontinence
How is bacterial prostatitis treated?
Use antibiotic that penetrates the blood-prostate barrier (sulphonamides, fluoroquinolones)
Treat for 4 weeks
How is subclinical bacteriuria treated?
Treatment is not recommended
