AKI

Question 1

Define AKI

Answer 1

An abrupt (over hours to days) sustained rise in serum urea and creatinine due to a rapid decline in GFR leading to a failure to maintain fluid, electrolyte and acid-base homeostasis - it is usually but not always reversible or self limiting.

Question 2

What are the criteria for diagnosing AKI

Answer 2

1. Rise in creatinine > 26μmol/L in 48hrs
2. Rise in creatinine > 1.5 x baseline (best figure in last 3 months)
3. Urine output < 0.5mL/kg/h for more than 6 consecutive hours

Question 3

Give 3 pre-renal causes of AKI?

Answer 3

1. Hypovolaemia (could be due to dehydration or haemorrhage)
2. Hypotension (could be due to cirrhosis or shock)
3. Hypo-perfusion (either due to hypotension or use of NSAIDs or ACEi)
4. Low cardiac output

Question 4

Give 3 intrinsic causes of AKI?

Answer 4

1. Tubulointerstitial disease (most commonly acute tubular necrosis)
2. Glomerular disease e.g glomerulonephritis
3. Vascular lesions e.g vasculitis or malignant hypertension

Question 5

Give 3 post-renal causes of AKI

Answer 5

1. Obstruction of the ureter
2. Obstruction of the bladder neck
3. Obstruction of the urethra

Question 6

What are some risk factors for AKI?

Answer 6

Age, HF, Sepsis, Hypovolaemia, Haematological malignancy, Diabetes, Prostate cancer, Nephrotoxic drugs

Question 7

Briefly describe the epidemiology of AKI

Answer 7

Common (15% of hospital patients), about 25% of patients with sepsis and 50% of patients with septic shock will have AKI, common in elderly

Question 8

Give the signs and symptoms of AKI

Answer 8

1. Alteration of urine volume - oliguria initially and then large amounts of urine during recover phase
2. Biochemical abnormalities - hyperkalaemia, metabolic acidosis, hyponatraemia, hypocalcaemia
3. Symptoms of uraemia - Fatigue, weakness, anorexia, nausea and vomiting. Followed by confusion, seizures and coma. May be pruritus and bruising. Breathlessness occurs from a combination of anaemia and pulmonary oedema secondary to volume overload

Question 9

What investigations would you do in AKI?

Answer 9

1. Blood count - anaemia and high ESR - suggest myeloma or vasculitis as cause
2. MSU
3. Urine dipstick: Can suggest infection (leucocytes + nitrites) and glomerular disease (blood + protein)
4. US
5. ECG - arrhythmias
6. CXR - Pulmonary Oedema
7. Renal biopsy

Question 10

What is the treatment for AKI?

Answer 10

Treat underlying cause, stop nephrotoxic drugs, optimise fluid balance, RRT

Question 11

How would you treat the underlying cause?

Answer 11

Pre-renal:

1. Correct volume depletion with fluids
2. Treat sepsis with antibiotics

Intrinsic renal:
Refer early to nephrology if concern over tubulointerstitial or glomerular pathology

Post-renal:

1. Catheterise and consider CT of renal tract (CTKUB)
2. If signs of obstruction and hydronephrosis then think cystoscopy and retrograde stents or nephrostomy insertion

Question 12

Give examples of nephrotoxic drugs

Answer 12

NSAIDs e.g. aspirin, diclofenac, ibuprofen
ACE-inhibitor e.g. ramipril, lisonopril, perinopril
Gentamicin (antibiotic)
Amphotericin (anti-fungal)

Question 13

Give 3 indications for dialysis

Answer 13

1. Symptomatic uraemia including pericarditis or tamponade
2. Hyperkalaemia not controlled by conservative measures
3. Pulmonary oedema thats unresponsive to diuretics
4. Severe acids
5. High potassium
6. Tall T waves, low flat p waves, broad QRS or arrhythmias on ECG
7. Metabolic acidosis
8. Fluid overload that is resistant to diuretics

Question 14

Give 3 complications with RRT

Answer 14

1. Cardiovascular disease e.g. MI or cerebrovascular accident due to combination of hypertension and calcium/phosphate dysregulation
2. Infection
3. Amyloid accumulates in long-term dialysis and may cause carpal tunnel syndrome, arthralgia and fractures
   Malignancy is commoner in dialysis patients - may be due to cause of end-stage renal failure e.g. urothelial tumours