Acute Kindey Injury Flashcards

1
Q

Acute Kidney Injury (AKI) definition
- characterized by what?
- what do we see?

A

= abrupt ↓↓ in renal function
- characterized by sudden ∆ in creatinine and/or urine output
- retention of uremic toxins
- dysregulation of fluid, electrolytes, acid-base balance
- previously referred as acute renal failure…

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2
Q

Acute Renal Failure (ARF) =

A

= abrupt, sustained ↓ GFR; most severe AKI

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3
Q

Azotemia =

A

↑ blood nitrogen compounds (i.e. BUN, creatinine)

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4
Q

Uremia =

A

severe azotemia with adverse clinical manifestations

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5
Q

Traditional view of azotemia
- what this means for nephron loss
- what this means for timing

A

Traditionally …
- Azotemia = BUN + creatinine outside established reference ranges (>75% loss of nephron function) → very late diagnosis

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6
Q

Acute Kidney Injury = spectrum of renal injury + disease severity
- what is this spectrum
- what is the most sever form of AKI
- when is recovery possible?

A

Normal - Clinically non-detectable, non-azotemic injury
<><>
Intrinsic injury - dysfunction
<><>
structural damage - altered function
<><>
kidney failure - most severe stage of AKI = Acute Renal Failure
- Recovery (CKD stage 1)
- CKD stage 2-4
- death

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7
Q

Measures of Renal Function, and what they tell us

A

Urine specific gravity (USG)
- tubular function
- ability to concentrate and/or dilute urine
<><><><>
Serum creatinine (SCr)
- late surrogate marker of GFR
- elevation when ~75% of nephrons loss
<><><><>
Symmetric dimethylarginine (SDMA)
- earlier surrogate marker of GFR
- sensitive, but less specific
<><><><>
Urine output (UOP)

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8
Q

limitations of creatinine as a measurement

A
  • late surrogate marker of GFR
  • elevation when ~75% of nephrons loss
    <><>
  • It is possible to have functional loss of an entire kidney, but creatinine still within normal reference range!
    <><><><>
  • In early kidney disease, large changer in GFR relate to very small changes in creatinine.
  • Only in late kidney disease do small changes in GFR relate to larger creatinine changes
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9
Q

creatinine measurement within a 4h period that is consistent with AKI?
- therefore, what must we do for proper interpretation?

A
  • An increase in creatinine by 26.5 𝜇mol/L (even in the non-azotemic range) within a 48-hour period is consistent with AKI
    <><><>
    Therefore:
    1. look at changes outside established reference range
    2. evaluate for small changes in creatinine (26.5 𝜇mol/L) from baseline
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10
Q

Categories of Azotemia

A

Pre-renal (volume-responsive)
- 2° to hypoperfusion in a structurally normal kidney
<><>
Intrinsic / renal
- 2° to intrinsic kidney dysfunction
<><>
Post-renal
- 2° to urine flow / drainage obstruction

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11
Q

Pre-renal Azotemia
- causes
- lab results
- fixable? progression?

A
  • ↓ blood flow to functional kidneys impair solutes / toxins clearance, e.g.:
  • dehydration
  • hypovolemia
  • hypotension
    <><>
  • Usually ↑ BUN / creatinine with a concentrated USG
    <><>
  • Rapidly improves when underlying condition is corrected promptly
    > otherwise, may progress to intrinsic AKI
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12
Q

Intrinsic Renal Azotemia
- causes

A
  • Ischemic
    > Hemodynamic
    instability
    v Prolonged dehydration
    v Shock
    vAnesthesia (↓ BP)
    vRenal artery thrombosis
    vSepsis / SIRS
    <><>
    Infectious
  • Leptospirosis
  • Pyelonephritis
  • Borreliosis (Lyme)
  • Feline infectious peritonitis (FIP)
    <><>
  • Toxins / Drugs
    <><>
  • Neoplasia
    > Renal lymphoma
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13
Q

Intrinsic Renal AKI - Nephrotoxic drugs

A
  • NSAIDS
  • Aminoglycoside
  • Amphotericin B
  • ACE inhibitors
  • Furosemide
  • Cisplatin
  • Carboplatin
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14
Q

Intrinsic Renal AKI - Nephrotoxic toxins?

A
  • Ethylene glycol
  • Lilies 🐈
  • Grapes/raisins 🐩
  • Heavy metals (copper, lead)
  • Vit D3 analogs (psoriasis cream)
  • Vit D3 (cholecalciferol) rodenticide
  • Myoglobinuria / hemoglobinuria
  • Radiocontrast agents
  • Envenomation
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15
Q

Post-Renal Azotemia causes, how to fix . progression

A
  • Urine leakage (uroabdomen)
    > any part of the urinary tract
    <><>
    Urinary obstruction
  • urethral obstruction
  • bilateral ureteral obstruction
  • unilateral ureteral obstruction + ↓ renal function of contralateral kidney
    <><>
  • Restoration of urine flow / drainage rapidly resolves the azotemia
    > prolonged obstruction may lead to renal parenchymal injury
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16
Q

AKI history

A

normal > (brief) polyuria > oliguria > anuria
<><><><>
Non-specific
- lethargy, anorexia, vomiting, diarrhea
<><><>
Urine production (last known urination!) - polyuria, oliguria, anuria
<><><>
- Polydipsia, accompanies polyuria (overshadowed by anorexia)
- Less common: seizures, dyspnea, etc.
- Vaccination status (Leptospira spp. bacterins)

17
Q

Physical Examination findings for AKI

A
  • Hydration status: dehydrated vs. euhydrated vs. overhydrated
  • Halitosis, oral ulceration, tongue tip necrosis
  • Bradycardia, arrhythmias (hyperkalemia)
  • Normal-to-enlarged, painful kidneys
  • Melena, diarrhea (uremic gastropathy)
  • Hypertension
  • Bladder size
  • Cutaneous bruising (thrombocytopenia, uremic thrombocytopathia)
18
Q

Acute vs. Chronic Kidney Disease

A

AKI has:
- History of illness: Shorter vs longer
- Body condition score (BCS) vs decreased
- Abdominal (renal) pain: present vs absent
- renal size: Normal-to-enlarged vs Normal-to-small, irregular
- Packed cell volume (PCV): Normal-to-increased (hemoconcentration) vs Reduced (non-regenerative anemia)
- Potassium (K+): Normal-to-hyperkalemia vs Normal-to-hypokalemia

19
Q

Bloodwork for AKI may show:

A

Variable findings
<><>
Complete blood count
- leukocytosis, neutrophilia (infectious, inflammation)
- thrombocytopenia(leptospirosis)
<><><><>
Serum biochemistry profile
- azotemia
- hyperphosphatemia
- hyperkalemia
- hypercalcemia (vit D3 analog intoxication)
- ionized hypocalcemia (ethylene glycol intoxication)
- elevated liver enzymes +/- hyperbilirubinemia (leptospirosis)

20
Q

Urinalysis & Urine Culture (prior to fluid therapy, antibiotics) for AKI:

A

Urinalysis
- isosthenuria = 1.008 – 1.012
- ± glucosuria without hyperglycemia,± proteinuria
- active urine sediments:
> pyuria, hematuria, bacteriuria (UTI)
> granular casts
> calcium oxalate monohydrate crystals (picket fence) > suggestive of ethylene glycol intoxication
<><><><>
Aerobic urine culture
- cystocentesis / catheterization sample
- rule out UTI (source of pyelonephritis), guide antimicrobial therapy (UTI)

21
Q

Diagnostic Imaging findings for AKI:

A

Variable findings:
<><><><>
Abdominal ± pelvic radiographs
- renal size: 2.5-3.5x L2 (dogs), 2-3x L2 (cats)
- radio-opaque uroliths
- bladder silhouette, loss of serosal details, pelvic fx
<><><>
Abdominal (urogenital) ultrasonography
- normal / enlarged kidneys with normal architecture
- pyelectasia, hydronephrosis (pyelonephritis, ureteral obstruction)
- echogenic “rim” at corticomedullary junction (EG intoxication)
- diffuse thick cortex & perirenal hypoechoic halo (lymphoma?)
- peritoneal, retroperitoneal effusion
- uroliths, cystitis

22
Q

Infectious Disease Testing: Leptospirosis
- for AKI
> how do we do it?

A
  • Real-time Polymerase Chain Reaction (PCR) – detects antigens
  • blood, urine
  • false –ve: rapid organism clearance following antibiotics
    <><><><>
  • WITNESS® Canine Leptospira Antibody Test Kit – detects IgM
    <><><>
  • Microscopic Agglutination Test (MAT) – detects IgG
23
Q

Infectious Disease Testing: Borreliosis (Lyme)
- for AKI
> tests

A
  • SNAP® 4Dx® Plus test – qualitative, detects antibodies
  • Lyme Quant C6® test – quantitative serologic testing