AKI

Question 1

Define oliguria and anuria

Answer 1

Oliguria - little urine <400ml/day

Anuria < 100ml/day

Question 2

Define AKI. What is it measured in?

Answer 2

Acute Kidney Injury is a syndrome of decreased renal function (decline in actual GFR) that occurs over hours/days <2 weeks. Measured in serum creatinine or urine output decline.

Increase in SCr > 26.5umol/L in 48 hrs
Increase in serum creating by 1.5 x baseline within 7 days
Urine volume <0.5ml/kg/hr for 6 hours

Question 3

What is the first stage of AKI?

Answer 3

SCr > 26.5umol/L or 1.5-2 times the baseline

URine output < 0.5ml/kg/hr for 6-12h

Question 4

What is the 2nd stage of AKI

Answer 4

SCr > 2-2.9 x baseline

Urine output <0.5ml/kg/hr for >12h

Question 5

What is the 3rd stage of AKI

Answer 5

SCr >354umol/L or 3 x baseline or initiated on RRT

<0.3ml/kg/hr for > 24h or anuria for 12h

Question 6

What are the limitations of using serum creatining

Answer 6

Increased muscle mass - increased serum creatinine

Question 7

Risk factors for AKI

Answer 7

Pre-existing CKD
Age
Male sex
Comorbidity
CVS disease
Malignancy
Chronic liver disease
Complex surgery

Question 8

Causal categories of AKI

Answer 8

Pre-renal (reduced perfusion to the kidney)
Renal (intrinsic damage to kidneys)
Post-renal (obstruction to the urine)

Question 9

Describe pre-renal AKI

Answer 9

Decreased renal perfusion
If BP falls below a threshold the kidney is able to maintain blood flow and GFR declines.
reversible if recognised quickly

Question 10

Give causes of pre-renal kidney failure

Answer 10

Hyppovolaemia - haemorrhage, diarrhoea and vomitting, burns, pancreatitis
Systemic vasodilation - sepsis, cirrhosis, drugs, anaphylaxis
Reduced CO - LV dysfunction, MI, cariogenic shock, tamponade
Renal preglomerular vasoconstriction - sepsis, hepatorenal syndrome, hypercalcaemia, drugs - NSAIDs
Postglomerular vasodilation - ACE inhibitors, ATII antagonists

Question 11

What happens if pre-renal AKI is not treated promptly?

Answer 11

Kidney cells become hypoxic

Acute tubular necrosis occurs.

Question 12

What is acute tubular necrosis?

Answer 12

Damage to tubular cells so that they cannot reabsorb water and salt efficiently.
It is caused by ischaemia - fall in renal perfusion
Nephroxins - damage toe epithelial cells - cell death and shedding, all drugs are potentially nephrotoxins
sepsis

Question 13

Give the possible causes of renal AKI

Answer 13

Golmerular:
Acute glomerulonephritis - immune disease affecting the glomerulus
Acute tubular necrosis (prolonged pre-renal diseasE)

Acute tubule-interstitial nephritis - inflammation of the interstitial of the kidneys surrounding tubules:
Drug reaction - NSAIDs, antibiotics, PPIs
Infection - acute pyelonephritis

Vessels - vasculitis, DIC

Question 14

Describe post-renal AKI and give causes.

Answer 14

Obstruction to urine flow after it has left the tubules.
This causes a rise in intratubular pressure, dilation of the renal pelvis and reduced renal function.
Obstruction at ureter, bladder, urethra

Question 15

Where and how can post-renal AKI obstruction occur?

Answer 15

Within the lumen:
Renal stones, blood clot, stricture, tumour of renal tract

Within wall: (usually chronic)
Ureteric stricture, congenital

Pressure from external compression:
Pelvic malignancy, prostatic hypertrophy, aortic aneurism, retroperitoneal fibrosis

Question 16

Give some exogenous and endogenous nephrotoxins

Answer 16

exogenous: NASAIDs, ATII antagonists, ACE-i
endogenous: myoglobin bilirubin

Question 17

What is acute glomerulonephritis?

Answer 17

Immune disease of the glomerulus
primary - kidneys only
secondary - part of systemic response

Question 18

What is acute tubulointerstital nephritis

Answer 18

Inflammation of the kidney interstitial due to infection or toxins

Question 19

what sign indicates post-renal failure?

Answer 19

Anuria
History of renal stones/prostatism/pelvic surgery
Palpable bladder
Pelvic masses
Enlarged prostate

Question 20

Describe the presentation in sepsis

Answer 20

Pyrexia and rigors (sudden feeling of cold or shivering)
Vasodilation, warm peripheries
Bounding pulse
Rapid capillary erfill
Hypotension

Question 21

Describe the presentation of cardiac failure

Answer 21

Gallop rhythm
Raised BP
Raised JVP
Pulmonary oedema (basal crackers and dyspnoea
Peripheral oedema (sacrum ankle)

Question 22

Give investigations to carry out in AKI, what are they to check for?

Answer 22

Serum biochemistry U&E - urea and creatinine
ECG - hyperkaleamia
Urine dipstick - protein, blood
Urine microscopy - different casts
Ultrasound Scan - kidney size/asummetry/stones
CXR -pulmonary oedema/ fluid overload/infection
LFT - hepatorenal sundrome
Immunological test for intrinsic renal disease

Question 23

What serum biochemistry is expected and possible in AKI?

Answer 23

Raised urea and creatinine in all AKI

Hyperkalaemia, hyponatraemia, hypocalcaemia, hyperphosphataemia possible

Question 24

ECG changes in hyperkalaemia

Answer 24

Tall T
Small/absent P
Increased P-R interval
Wide QRS
Asystole

Question 25

What does proteinuria/haematuria suggest?

Answer 25

intrinsic renal disease

Question 26

Describe what is seen on microscopy in pre-renal AKI, ATN, glomerulonephritis

Answer 26

Pre-renal - hyaline cast (aggregation of protein in concentrated urine (normal))
ATN - muddy brown casts
Glomerulonephritis - RBC casts

Question 27

What immunological tests should be carried out? What do they indicate?

Answer 27

Anti-nuclear antibody (ANA) - systemic lupus erythematous (autoimmune disease)
Anti-neutrophil cytoplasmic antibody (ANCA) - systemic vasculitis
Anti-glomerular basement membrane antibodies (AGBM) - goodpasture’s disease (immune attack of lung and kidney BMs leading to lung bleeding and kidney failure

Question 28

What do small kidneys suggest? Asymmetry?

Answer 28

Small - CKD

Asymmetry - renal vascular disease