Acute renal failure (pre-renal)

Question 1

How common is it?

Answer 1

Very common in acute illness. Stage 1 AKI is found in more than 15% of emergency hospital admissions. AKI with plasma creatinine >500micromol/L is diagnosed in 2 to 7.5 per 10,000 adult population per year in the UK.

Injury counts when serum creatinine is 2X increased from the baseline

Question 2

What risk factors are there?

Answer 2

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Hx of AKI.

Chronic kidney disease (eGFR<60mL/min/1.73m2).
Symptoms or history of urological obstruction or conditions which may lead to obstruction.

Chronic conditions such as heart failure, liver disease and diabetes mellitus.

Neurological or cognitive impairment or disability (which may limit fluid intake).

Sepsis.

Hypovolaemia.

Oliguria (urine output <0.5mL/kg/hour).

Nephrotoxic drug use within the last week (e.g. ACE inhibitor, NSAID, ARBs and diuretics.

Exposure to iodinated contrast agents within the last week.

Question 3

How does it present?

Answer 3

Suspect AKI if presented with an acute illness and any of the risk factors above.

Also new onset or significantly worsening urological symptoms.

Symptoms or signs of a multi-system disease affecting the kidneys and other organ systems.

Alteration of urine volume: Oliguria usually occurs in the early stages.

Recovery of renal function typically occurs after 7-21 days and in the recovery phase, which may last some weeks, there is often passage of large amounts of dilute urine.

Biochemical abnormalities:

• Hyperkalaemia
• metabolic acidosis
• hyponatraemia (due to water overload as a result of continued drinking)
• hypoglycalcaemia due to reduced production of Vit D
• hyperphosphatemia due to phosphate retention.

Question 4

Signs on examination?

Answer 4

Even when symptoms and signs develop they are very non-specific.

People may develop nausea, vomiting, drowsiness, breathlessness because of pulmonary oedema or metabolic acidosis and arrhythmias.

Symptoms in AKI are usually related to the underlying causes, rather than the AKI itself.
All patients with AKI should be examined for evidence of obstruction (enlarged palpable kidneys or bladder, large prostate on rectal examination, pelvic masses on vaginal examination in women).

Question 5

Investigations

Answer 5

Blood count: Anaemia and a very high ESR may suggest a myeloma or a vasculitis as the underlying cause.

Urine and blood cultures to exclude infection. Urine dipstick testing and microscopy: glomerulonephritis is suggested by haematuria and proteinuria on dipstick testing and red cell casts on microscopy. Renal ultrasound to assess for size.

Histological investigations: renal biopsy should be performed in every patient with unexplained AKI and normal-sized kidneys.

Question 6

Treatment

Answer 6

Fluid correction.
Sodium and potassium is restricted.
Stop nephrotoxic drugs and adjust the doses of others.