AKI, CKD and renal replacement therapy

Question 1

Define AKI

Answer 1

A significant deterioration in renal function, which is potentially reversible, over a period of hours or days

Question 2

What is the RIFLE criteria?

Answer 2

Classification of the severity of AKI:

Risk = 1.5x increase in Creatinine, 25% decreased GFR and less than 0.5ml/kg urine output for 6 hours
Injury = 2x increase in Creatinine, 50% decreased GFR and less than 0.5ml/kg urine output for 12 hours
Failure = 3x increase in Creatinine, 75% decreased GFR and less than 0.5ml/kg urine output for 24hrs (or anuria for 12 hours)
Loss (of kidney function) = requires RRT for >4 weeks
End (stage kidney failure) = requires RRT for >3months

Question 3

What is the AKIN criteria?

Answer 3

Modified classification of AKI (from RIFLE) designed to increase sensitivity and specificity of AKI:

Stage 1 = Creatinine >26.4 (1.5-2x increase) and less than 0.5ml/kg urine output for 6 hours
Stage 2 = 2-3x increase in Creatinine and less than 0.5ml/kg urine output for 12 hours
Stage 3 = Serum Creatinine >354 (>3x increase) and less than 0.3ml/kg urine output for 24 hours (or anuria for 12 hours)

Question 4

How can the causes of AKI be classified?

Answer 4

Pre-renal failure
Intrinsic renal failure
Post-renal failure

Question 5

What can cause pre-renal failure?

Answer 5

Renal hypoperfusion (reduced blood supply/ pressure to the kidneys) 
Can be caused by systemic hypotension (e.g. hypovolaemia caused by bleeding or dehydration, sepsis) or local (e.g. renal artery stenosis or drugs e.g. ACEi or NSAIDs) 

[Approx. 85% of AKIs are pre-renal]

Question 6

What can cause intrinsic renal failure?

Answer 6

1. Primary renal disease (e.g. glomerulonephritis)
2. Secondary renal disease (e.g. diabetes, myeloma)
3. Interstitial nephritis (usually drug-induced)
4. Secondary acute tubular necrotis (caused by prolonged renal hypoperfusion)

Question 7

What can cause post-renal failure?

Answer 7

Obstruction or blockage of drainage from the kidneys

[Nb. important to distinguish where blockage is above anatomically e.g. above bladder - identified through ultrasound and also whether blockage is in the lumen, tubular walls or outside of the walls]

Question 8

What can cause blockages in various layers of the urinary tract walls?

Answer 8

Lumen = stones
In wall = tumour
External = compression from other anatomical structures

Question 9

What clinical features would you want to establish when taking a history from someone with AKI?

Answer 9

Onset
Precipitating factors 
Urinary symptoms 
Chronic symptoms
Systemic features (e.g. autoimmune disease) 
Relevant PMH/FH 
Drug history

Question 10

What clinical features would you want to establish on examination of someone with AKI?

Answer 10

Fluid status (e.g. peripheral perfusion or oedema, JVP, pulse rate/rhythm/volume, lying and standing BP, tissue turgor)
Signs of sepsis (e.g. fever, tachycardia, tachypnoea)
Abdominal (e.g. ascites, masses, bladder)
Respiratory (pulmonary oedema/ effusion)
Cardiac (pericardial rub)
CNS (drowsiness, confusion)
Skin (e.g. rashes)

Question 11

What tests should be done when investigating renal function?

Answer 11

Bloods (biochemistry - Cr, eGFR, Na, K, Bic, Ca, CRP; haematology - Hb; immunology) 
Urine test (dipstick, output, albumin-creatinine ratio - ACR) 
Radiological (Renal USS, CXR, CT renal angiogram)

Question 12

What is the initial management for a patient with AKI?

Answer 12

Rectify life-threatening effects 
Generic (e.g. fluid, electrolytes) 
Review medication 
Close observation 
Diagnose cause and treat/ seek specialist advice

Question 13

What are the life-threatening consequences of AKI?

Answer 13

Hyperkalaemia (causes arrhythmias and cardiac arrest)
Fluid overload (can lead to respiratory arrest)
Hypotension (can lead to cardiac arrest)
Acidosis

Question 14

What ECG changes will be seen in patients with hyperkalaemia?

Answer 14

Peaked ("tented") T waves 
Prolonged P-R interval 
Prolonged QRS duration 
Loss of P waves
VF/ Asystole

Question 15

What is the difference between AKI and CKD?

Answer 15

AKIs = acute (hours or days) and reversible 
CKD = months/ years and irreversible

Question 16

What are the possible complications of CKD?

Answer 16

CVD 
Hypertension 
Anaemia
Bone-mineral metabolism 
Poor nutritional and functional status 
Progression of CKD 
AKI

Question 17

How is CKD measured?

Answer 17

Test for renal excretory functions (e.g. Creatinine, Cystatin C, eGR)
Test for albuminuria (proteinuria)

Question 18

What is classed as significant progression of CKD?

Answer 18

Sustained decrease in GFR of 25% or more and a change in GFR category within 12 months

OR

Sustained decrease in GFR of 15ml/min/1.73m per year

Question 19

What factors are associated with progression of CKD?

Answer 19

Hypertension (associated with level of eGFR) 
Diabetes Mellitus 
Albuminuria 
CVD 
Smoking 
Ethnicity 
NSAIDs

Question 20

What are the consequences of late presentation in patients with CKD?

Answer 20

Higher mortality, morbidity, hospital stay, costs etc.
Lack of vascular access
No possibility of pre-emptive transplantation

Question 21

What is established renal failure?

Answer 21

Stage of CKD where RRT is required to safely sustain life

Question 22

What are the options for renal replacement therapy?

Answer 22

1. Haemodialysis
2. Peritoneal dialysis
3. Transplantation (from deceased or living donor) - best option
4. Conservative care

Question 23

What is the disadvantage of haemodialysis as RRT?

Answer 23

Time consuming (requires 3 x 4hrs in hospital per week)

Question 24

What is the advantage of peritoneal dialysis as RRT?

Answer 24

Can be done at home

Question 25

What factors should be considered when discussing RRT modalities with patients with CKD?

Answer 25

Physical/ social factors (dexterity, mobility, support, employment) 
Medical factors (abdominal surgery, vascular disease, hypotension) 
Geographical factors (distance from haemodialysis unit, home environment)