acute kidney injury (AKI)

Question 1

definition of AKI

Answer 1

Acute kidney injury (AKI), previously known as acute renal failure (ARF), is an acute decline in renal function, leading to a rise in serum creatinine and/or a fall in urine output.[1] The change in terminology emphasises that kidney injury presents as a disease spectrum from mild renal impairment to severe renal failure.[1][2][3] A standardised definition is important to facilitate clinical care and research.[4] AKI may be due to various insults such as impaired renal perfusion, exposure to nephrotoxins, outflow obstruction, or intrinsic renal disease. The resulting effects include impaired clearance and regulation of metabolic homeostasis, altered acid/base and electrolyte regulation, and impaired volume regulation.

Question 2

classification

Answer 2

Classification based on pathophysiology
Pre-renal: failure due to impaired renal perfusion, with an appropriate renal response.
- hypotension of any cause
Intrinsic: failure due to direct injury to renal parenchyma.
- drugs, glomerulonephritis, vasculitis
Post-renal: failure due to obstruction of urinary outflow.
- obstruction

Question 3

signs and symptoms

Answer 3

May be none, or fatigue, malaise, rash, joint pains, nausea/ vomiting, chest pain, palpitations, shortness of breath, fluid overload, abdominal pain, oliguria, hypo- or hypertension

Question 4

investigations

Answer 4

Urgent ABG/VBG for K+
• ECG for hyperkalaemic changes
• Bloods: U&ES, Ca2+, PO43–, FBC, ESR, CRP, clotting, LFTS, CK in all. Consider ‘renal
screen’: protein electrophoresis, hepatitis serology, autoantibodies (ANCA, ANA,
anti-GBM), complement, ASOT, rheumatoid factor, cryoglobulins.
• Urine: dipstick, send for microscopy, culture, albumin/creatinine ratio
• renal USS
• CXR (check for heart failure)

Question 5

treatment

Answer 5

pre-renal azotaemia:

• volume expansion / RBC transfusion
• with severe hypotension: vasopressor
• with volume overload: diuretic
• with uraemia, severe metabolic acidosis, hyperkalaemia refractory to medical management, or volume overload unresponsive to diuretics: renal replacement therapy (diuretics)

intrinsic renal failure:
=> same treatment as pre-renal, but treat underlying cause too!

obstructive renal failure:
1. bladder catheterisation
2. relief of obstruction above bladder neck
=> treat other problems accordingly like above

Question 6

complications

Answer 6

• hyperphosphataemia
• uraemia
• volume overload
• hyperkalemia
• metabolic acidosis
• chronic progressive kidney disease
• end stage renal disease

Question 7

prognosis

Answer 7

Recovery for AKI is variable and depends on cause of injury and the severity and duration of AKI.

There is an independent association of AKI with a higher risk of death. In-hospital mortality rates associated with AKI vary from 6% to 80%, and there is increased long-term mortality in those with AKI surviving hospitalisation.

Up to 6% of patients admitted to the intensive care unit have AKI requiring renal replacement therapy. In hospital, when AKI requires dialysis, mortality exceeds 50%; those with multi-organ failure are at greatest risk. Mortality rates are high due to death from underlying disease and complications, not just the AKI.