Clinical AKI

Question 1

What classification scales are used in AKI?

Answer 1

• RIFLE (risk, injury, failure, loss and end-stage kidney disease) and AKIN (acute kidney injury network 1-3) criteria
• Modest increases in serum creatinine (60-110/120 mmol/L) represent significant renal injury

Question 2

What factors increase the risk of AKI?

Answer 2

•	Older adult-kidney function declines with age
•	Comorbidity
	Heart failure
	Diabetes (micro and macrovascular disease)
	Hypertension
	Vascular disease (atheroma)
	Chronic kidney disease
•	Medications
	Anti-hypertensives (ACE inhibitors)
	Diuretics
	NSAIDs
	Antibiotics and antimicrobials

Question 3

What are the pre-renal causes of AKI?

Answer 3

• Reduced renal perfusion leading to reduced glomerular filtration
• Prolonged hypoperfusion= acute tubular injury and necrosis
 Fluid losses leading to hypotension
 GI losses, haemorrhage, diuresis (drugs/ diabetes)
 Hypotension secondary to infection and sepsis
 Hypotension due to reduced cardiac output
 Hypotension due to medication
 Oedematous states including liver disease, heart failure and nephrotic syndrome
 Selective renal ischaemia
 Vascular occlusion

Question 4

What are the intrarenal causes of AKI?

Answer 4

• Intrarenal vascular injury
 Systemic vasculitis
 Accelerated (malignant hypertension)
 Emboli
• Glomerulonephritis
• Tubular injury
 Acute tubular necrosis
 Rhabdomyolysis (massive muscle necrosis- myoglobin causes cell death in tubes)
 Interstitial nephritis especially drugs
 Drug induced tubular injury (antimicrobials/ anti-cancer)
 Myeloma (tumour of plasma cells- filtration of light chains form crystal so occlusion)

Question 5

What are the postrenal causes of AKI?

Answer 5

• Most common cause is bladder outflow obstruction
 Prostate enlargement-hyperplasia, malignancy
 Neurogenic bladder
• Ureteric obstruction (usually bilateral)
 Malignancy-bladder, cervical
 Stones
 Surgical (pelvic)
 Retroperitoneal fibrosis

Question 6

Describe glomerulonephritis

Answer 6

• Wide spectrum of presentation from asymptomatic urinalysis abnormalities to severe AKI
• Rapidly progressive glomerulonephritis
 Systemic vasculitis usually anti-neutrophil cytoplasmic antibody positive
 IgA nephropathy- acute episodes precipitated by upper respiratory tract infection
 Post-infectious- streptococcal infection
 Lupus nephritis
 Infective endocarditis (heart valve= inflammatory response)

Question 7

Describe rapidly progressive glomerulonephritis

Answer 7

•	May have systemic symptoms
	Fever, night sweats
	Myalgia, arthralgia
	Rash (vasculitic)
•	Hypertension
•	Oedema (peripheral)
•	Elevated creatinine (AKI)
•	Urinalysis: blood >1+ and protein >2+ (a.k.a an active urinary sediment)

Question 8

Describe interstitial nephritis

Answer 8

• Most commonly associated with drugs (any drug can do cause it)
 Antibiotics-especially penicillin’s
 Non-steroidal anti-inflammatory drugs
 Proton pump inhibitors
 Diuretics
• Consider for a case of AKI. Clues include:
 Rash
 Fever
 Eosinophilia (blood count)
 Sterile pyuria i.e., leucocyte positive urinalysis

Question 9

What is considered in the initial assessment of AKI?

Answer 9

• Rising creatinine, oliguria
• Clinical context is key
 Pre-renal-fluid losses, infection, drugs, surgery, co-morbidities
 Intrarenal-systemic illness, drugs
 Post-renal-urinary symptoms
• Fluid status: Hypovolaemic, fluid overloaded, euvolaemic
• Exclude urinary retention
 Patient passing urine, palpable bladder, lower urinary tract symptoms
• Urinalysis
 Does this indicate a possible glomerular disease or infection?
• Check the drug chart: Any drug causes or drugs to withhold

Question 10

What are the investigations of AKI?

Answer 10

• Urea and electrolytes, look out for hyperkalaemia (K+>6.5 mmol will need treatment)
• Full blood count, CRP
• Infection screen-urine, blood, would swabs, drain fluids, sputum, stool
• Specific blood tests e.g.
 Autoantibodies e.g. ANCA, dsDNA, anti-GBM
 Myeloma screen-serum and urine electrophoresis
 Complement (can be low in post-infectious GN, lupus)
• Ultrasound renal tract or bladder scan
 Urinary obstruction and renal size

Question 11

What are the principles of AKI management?

Answer 11

• Treat hypovolaemia/fluid overload
• Treat underlying cause such as infection
• Withhold nephrotoxic drugs e.g.
 ACEi/ARB
 NSAIDs
 Diuretics
 Drugs that may accumulate in renal failure (metformin- lactic acidosis/ opioids)
• Relieve urinary obstruction (catheter/ procedure)