Acute Kidney Injury Flashcards
What is AKI?
Abrupt deterioration in renal function, usually over hours/days. Results in a failure to maintain fluid, electrolyte and acid-base balance.
What is pre-renal AKI?
Decreased renal perfusion pressure
What is intrinsic renal AKI?
Pathology of the vessels, glomeruli, or tubules-interstitium.
What is post-renal AKI?
Obstruction of urinary outflow.
What can causes the impaired perfusion in pre-renal AKI?
Cardiac failure Sepsis Blood loss Dehydration Vascular occlusion
What can cause glomerulonephritis, small-vessel vasculitis and acute tubular necrosis in intrinsic renal AKI?
Drugs
Toxins
Prolonged hypertension
What can cause Interstitial nephritis in intrinsic renal AKI?
Drugs
Toxins
Inflammatory disease
Infection
What can cause obstruction of urinary flow in post-renal AKI?
Retroperitoneal fibrosis Benign prostatic enlargement Bladder cancer Prostate cancer Cervical cancer Urethral structure/valves Meatal stenosis
Define meatal stenosis.
Meatal stenosis is an abnormal narrowing of the urethral opening (meatus).
Define oliguria?
Decreased urine output (<400ml/day)
What is the most common underlying pathophysiological cause of AKI?
Acute tubular necrosis
What causes acute tubular necrosis?
Under perfusion and reduced renal blood flow with intrarenal microvascular vasoconstriction leads to a decrease in the delivery of O2 increasing tubular hypoxia, leading to tubular necrosis.
Can also be caused by nephrotoxic drugs.
Why is acute tubular necrosis reversible?
Tubular cells have the ability to regenerate rapidly and to reform the disrupted tubular basement membrane - which is why ATN is reversible.
What are the 3 types of tubular renal AKI?
Acute tubular necrosis
Acute interstitial nephritis
Myeloma / Tumourlysis / Rhabdomyolysis
What can cause acute interstitial nephritis?
Allergic reaction - drug related
Can also be caused by infection e.g UTI
How do you test of post-renal obsturction of the urinary tract?
Ultrasound scan.
Pruritis
Severe itching of the skin
What is the major respiratory complication of AKI?
Shortness of breath due to pulmonary oedema.
How is GFR affected in post renal AKI?
Postrenal failure is caused by obstruction of the urinary tract, leading to increased intratubular pressure and a fall in GFR.
What can cause intratubular obstruction in intrinsic AKI?
Blockage of the tubules by protein (rhabdomyolysis and myeloma).
What can urine biochemistry help identify in investigation?
Whether the AKI is renal or pre-renal.
Why is an ultrasound carried out in cases of AKI?
To exclude post-renal obstruction.
What are the two major concerns of AKI?
Hypovolaemia and hyperkalaemia.
Hyperkalaemia
High potassium
Hypernatremia
High sodium
Interstitial nephritis is what type of AKI?
Intrarenal
Interstitial nephritis is usually caused by what?
Type 1 or Type IV hypersensitivity reaction caused by drugs such as NSAID’s, Diuretics or penicillin.
What is renal artery stenosis?
The narrowing of one or both renal arteries.
What can cause renal artery stenosis?
Atherosclerosis
Fibromuscular dyplasia
Fibromuscular dysplasia
Fibromuscular dysplasia (FMD) is a non-atherosclerotic, non-inflammatory disease of the blood vessels that causes abnormal growth within the wall of an artery.
Post renal AKI
Due to obstruction of urine from the kidneys leading to a build up of pressure and urine.
Name two nephrotoxic drugs that can cause intrarenal aki.
NSAIDS
ACE inhibitors
Why does aki cause pulmonary oedema?
As the kidneys are unable to filter blood, there is a build up of fluid hypervolemia. Which leads to leakage of fluid into the lung causing pulmonary oedema.
Nephrotoxic syndrome
Nephrotic syndrome is a kidney disorder that causes your body to pass too much protein in your urine. Nephrotic syndrome is usually caused by damage to the glomerular capillaries.
What is the triad of symptoms seen in nephrotoxic syndrome?
Oedema
Proteinuria
Low albumin levels in the blood
What is the major complication of nephrotoxic syndrome?
Oedema
How does nephrotoxic syndrome increase the risk of clotting?
Nephrotic syndrome increases the amount of anti-thrombin III lost in the urine.
Due to decreased protein in the blood the liver also activates protein synthesis increasing the number of clotting factors produced.
NICE Criteria for AKI:
Rise in creatinine of ≥ 25 micromol/L in 48 hours
Rise in creatinine of ≥ 50% in 7 days
Urine output of < 0.5ml/kg/hour for > 6 hours
Risk factors for AKI:
Consider the possibility of an acute kidney injury in patients that are suffering with an acute illness such as infection or having a surgical operation. Risk factors that would predispose them to developing acute kidney injury include:
CONTRAST CT
ACE inhibitors / NSAIDS both nephrotoxic
usual risk factors for everything…
Whenever someone asks you the cause of renal impairment always answer “the causes are pre-renal, renal or post-renal”. This will impress them and allow you to think through the causes more logically.
Whenever someone asks you the cause of renal impairment always answer “the causes are pre-renal, renal or post-renal”. This will impress them and allow you to think through the causes more logically.
Treatment of AKI:
Fluid rehydration with IV fluids in pre-renal AKI.
Stop nephrotoxic medications such as NSAIDS and antihypertensives that reduce the filtration pressure (i.e. ACE inhibitors).
Relieve obstruction in a post-renal AKI, for example insert a catheter for a patient in retention from an enlarged prostate.
What are the complications:
Hyperkalaemia
Fluid overload, heart failure and pulmonary oedema
Metabolic acidosis
Uraemia (high urea) can lead to encephalopathy or pericarditis.
