Kidneys: AKI, CKD

Question 1

What are the 6 main functions of the kidney

Answer 1

Electrolyte, fluid balance

Waste clearance

pH regulation

Hormone action site
-ADH, Aldosterone, PTH, ANP

Hormone production site
-renin, vitamin D, erythropoietin, prostaglandins

Gluconeogenesis

Question 2

Why are the kidneys vulnerable to damage?

What conditions are bad for the kidneys

Answer 2

20% of CO => kidneys
-PT in cortex needs rich supply

Hypotension, hypoxia

Question 3

Describe the 3 stages of AKIs
- serum creatinine
- urine output

Answer 3

Stage 1
C 1.5-1.9x from baseline
+26.5umol/L in 2 days
U <0.5ml/Kg/h for 6-12hrs

Stage 2
C 2-2.9x from baseline
U <0.5ml/Kg/h for 12+hrs

Stage 3
C 3x from baseline
     \+353.6umol/L
U <0.3ml/Kg/h for 24+hrs
     anuria for 12+hrs

Question 4

What are some causes of prerenal AKIs

• Volume depletion
• Drugs

Answer 4

Volume depletion

• hypovolemia
• renal artery stenosis

Drugs

• NSAIDs => low PGIs => no afferent VD
• ACEi => low Ang2 => no efferent VC

Question 5

What are some causes of intrinsic AKIs

• ATN
• Acute glomerulonephritis
• Acute interstitial nephritis
• Vascular

Answer 5

ATN
Ischemia
Nephrotoxics
-radiocontrast, aminoglycosides
-heme from rhabdomyolysis, hemolysis
-crystals

AIN

• penicillin, NSAIDs, allopurinol, furosemide
• infection
• systemic disease

Glomerulonephritides
Vasculitis

Question 6

What are some causes of post renal AKIs

Answer 6

Obstruction => hydronephrosis, loss of corticomedullary diff

• stones
• strictures
• BPH, cancers
• retroperitoneal fibrosis

Question 7

What are the 4 consequences of AKIs

How would you manage this

Answer 7

Supportive management and address underlying cause

Reduced urine output => pulmonary, peripheral edema

• diuretics
• ventilation/intubation if severe

Uraemia
-pericarditis, pleurisy, encephalopathy => RRT

Hyperkalaemia (5.5+)

• Ca glucoronate
• Insulin dextrose
• Remove K (Ca resonium/loop/dialysis)

Metabolic acidosis

• abdo pain, N+V, muscle weakness
• palpitations
• SOB

If not responding => RRT

Question 8

What is the prognosis of AKIs in hospital and why

Answer 8

Mortality increases due to large inflammatory response from kidney affecting the function of other organs

Question 9

What are the 4 steps in managing AKIs

Answer 9

1. Exclude life threatening complication
2. Address cause
3. Support
   
   • Nutrition
   • Ulcer prophylaxis
4. Avoid progression
   
   • Aminoglycosides, gentamicin
   • hypotension, hypovolemia

Question 10

What investigations would you do for a suspected AKI?

Answer 10

Urgent ABG, U&E => high urea, creatinine with electrolyte imbalances

Urinalysis

Imaging - within 24hrs if suspect obstructive cause

Question 11

Which drugs are safe to continue in AKI?

Answer 11

Aspirin at cardiac dose 75mg
Bb
Clopidogrel
Statins
Paracetamol
Warfarin

Question 12

Which drugs should you stop in AKI as renal function may deteriorate

Answer 12

NSAIDS except aspirin at cardiac dose
Aminoglycosides
ACEi, ARB
Diuretics

Question 13

Which drugs should you stop due to an increased toxicity risk?

Answer 13

Don’t usually worsen AKI
Digoxin
Lithium
Metformin

Question 14

Describe how kidney function changes in

• normal people
• AKI with recovery
• AKI without recovery
• CKD progressing to ESRF

Answer 14

Normally GFR declines with age

AKI with recovery => GFR suddenly declines but recovers
AKI without recovery => GFR suddenly declines and stays low

CKD progressing to ESRF => rapid decline in GFR

Question 15

How would you measure GFR
-what is it
What factors affect creatinine generation?
-decreased
-increased

Answer 15

Percentage of kidney function
MDRD formula
-age
-sex
-race
-creatinine

Decreased

• age
• female
• chronic illness

Increased

• black
• muscular
• meat eater

Question 16

What are the 5 stages of CKD
How frequently should you test each stage?
How would you judge the prognosis

Answer 16

Stage 1 => 90+ with evidence of CKD
-0-1x
Stage 2 => 60-89 with evidence of CKD
-0-1x
Stage 3 => 30-59
-1-2x
Stage 4 => 15-29
-2-3x
Stage 5 => U15, ESRF
-4x

Cause
GFR
Albuminuria/proteinuria

Question 17

Assessing for CKD

Answer 17

eGFR, ACR

• DM, HTN, CVD
• past AKI, urinary tract cond
• systemic disease with kidney involvement
• gout
• FHx of kidensy/ESRF
• incidental haematuria/proteinuria

If eGFR U60 => repeat eGFR within 2wks to rule out AKI (25%+ fall within 1wk)
If not AKi, repeat in 3 months => persistent reduced eGFR, high ACR

Question 18

Conservative management of CKD

Answer 18

Conservative

• smoking cessation, alcohol reduction
• healthy diet, weight
• annual vaccinations
• avoid NSAIDs, nephrotoxics where possible
• CV risk factor reduction

Manage conditions that affect kidneys

• lupus nephritis - immunosuppresion
• myeloma - chemo

Question 19

Conditions to look after in CKD

Answer 19

BP - correct hypervolemia then BP

Anemia - manage if symptomatic or HbU110
-Fe, B12, folate optimisation => EPO if needed

2ndary hyperPTH - dietary

• reduce PO4, PO4binders (Ca acetate)
• increase Ca, VitD, Adcal
• remove PT gland surgically

Metabolic acidosis => PO bicarbonate