Acute Kidney Injury Flashcards
What is acute kidney injury?
abrupt deterioration in renal function, usually over hours or days which is usually reversible
What is the name given to the stage classification of AKI based on urine output and serum creatinine?
KDIGO classification
Give two features of KDIGO stage 1 AKI:
1) serum creatinine 1.5-1.9 times the baseline
2) urine output <0.5mL/kg/h for 6-12 hours
Give two features of KDIGO stage 2 AKI:
- Serum creatine 2-2.9 times the baseline
- Urine output <0.5mL/kg/h for 6-12 hours
Give two features of KDIGO stage 3 AKI:
1) serum creatinine 3 times the baseline
2) anuria for 12+ hours
What percent of septic shock patients will have AKI?
50%
What are the three broad categories for causes of AKI?
1) pre-renal
2) renal
3) post-renal
Give 3 broad pre-renal causes of AKI?
- Hypovolaemia
- Hypotension
- low cardiac output
all causes reduced kidney perfusion and so a fall in GFR
Give an anatomical pre-renal causes of AKI?
renal artery stenosis
Give 8 causes of hypovolaemia:
1) dehydration
2) septic shock
3) reduced intake of fluids
4) haemorrhage/ blood loss
5) gut losses e.g. vomiting and diarrhoea
6) cardiac failure or shock
7) renal losses e.g. diuretics
8) burns
Give 9 renal (intrinsic) causes of AKI:
- Glomerulonephritis
- acute interstitial nephritis
- Acute tubular necrosis
4) rhabdomyolysis
5) acute cortical necrosis
6) contrast nephropathy
7) acute phosphate nephropathy
8) tumour lysis syndrome
9) hepatorenal syndrome
Does glomerulonephritis present with nephrotic or nephritic syndrome?
nephritic
What 4 drugs that can cause acute interstitial nephritis?
- Penicillin
- rifampicin
- NSAIDs
- Furosemide
Describe acute interstitial nephritis:
Acute hypersensitive reaction of the kidneys most often related to drugs, presenting with an allergic type picture with raised WCC, IgE and eosinophils
Give 3 causes of acute interstitial nephritis other than drugs:
- SLE
- sarcoidosis
- Sjogren’s syndrome
Give 6 symptoms of acute interstitial nephritis:
- Fever
- Rash
- Arthralgia
- eosinophilia
- mild renal impairment
- hypertension
What is arthralgia?
Discomfort, pain or inflammation arising from any part of a joint including cartilage, bone, ligaments, tendons or muscles.
Describe a histological finding associated with acute interstitial nephritis:
interstitial oedema and interstitial infiltrate in the connective tissue between renal tubules
What is the most common cause of AKI?
acute tubular necrosis
What are the two main causes of acute tubular necrosis?
1) ischaemia
2) nephrotoxins
True or false: serum urea creatinine ratio presents as normal in acute tubular necrosis
true
What is acute tubular necrosis?
An intrinsic acute kidney injury caused by ischaemic or nephrotoxic injury to renal tubular epithelial cells, which results in tubular dysfunction or detachment from the basement membrane.
How does acute tubular necrosis present?
- Hypotension
- Fluid depletion
- exposure to nephrotoxic agents
What is rhabdomylysis?
the breakdown of muscle tissue releases muscle fibre contents into the blood due to a crush or prolonged epileptic seizure
How can rhabdomyolysis cause AKI?
the myoglobin released from muscle tissue is toxic to tubular cells
Give two blood markers for rhabdomyolysis:
1) raised creatine kinase
2) raised myoglobin
Describe how you can differentiate between acute tubular necrosis and acute interstitial nephritis using urine dip test:
acute interstitial nephritis is inflammatory process meaning raised WCC will be found in urine - acute tubular necrosis is not inflammatory
Give 3 post-renal (obstructive) causes of AKI:
1) kidney stones in the ureter or bladder
2) benign prostatic hyperplasia
3) external compression of the ureter
What are 4 presentations associated with AKI?
1) oliguria
2) arrhythmias (raised potassium)
3) encephalopathy (raised urea)
4) pulmonary and peripheral oedema (fluid overload)
What is oliguria?
An output of less than 400ml a day
Give 3 core investigations used for AKI:
1) U+Es (sodium, potassium, urea, creatinine)
2) urinalysis (proteinuria, haematuria, nitrates)
3) renal ultrasound (if patients have no identifiable cause
Does renal scarring indicate acute or chronic kidney disease?
Chronic
Why is acute tubular necrosis often reversible?
tubular cells have the capacity to regenerate rapidly and to reform the disrupted basement membrane
Describe how to manage fluid and electrolyte balance in AKI:
1) twice daily clinical assessment of fluid and electrolytes
2) give 0.9% saline
Describe how to manage hyperkalaemia in AKI:
give IV sodium bicarbonate to reduce potassium levels
Give two instances where you should not give IV sodium bicarbonate to AKI patients:
1) patients with fluid overload - it can worsen pulmonary oedema
2) patients with hypocalcaemia - it can trigger tetany
Describe how to manage pulmonary oedema for patients with AKI:
1) give IV furosemide to induce diuresis
2) if this does not work due to renal impairment, dialysis or hemofiltration will be required
Describe how to manage nutrition for AKI patients: (2)
1) salt and potassium should be restricted
2) protein intake should be limited
Give two examples of renal replacement therapy:
1) haemodialysis
2) hemofiltration
Give 5 instances in AKI where renal replacement therapy would be used:
1) uncontrolled hyperkalaemia
2) pulmonary oedema unresponsive to diuresis
3) severe acidosis
4) when nephrotoxic drugs need removing
5) symptomatic uraemia
After how many weeks of treatment does renal function return following AKI?
1-3 weeks
What is acute cortical necrosis?
Glomerular ischaemic injury
True or false: acute cortical necrosis is reversible
False
Why is acute cortical necrosis not reversible?
glomerulosclerosis occurs
What is acute cortical necrosis?
Renal (kidney) cortical necrosis is death of the tissue in the outer part of the kidney (cortex) that results from blockage of the small arteries that supply blood to the cortex and that causes acute kidney injury.
What are the symptoms of acute cortical necrosis?
- Dark urine
- Decreased urine volume
- Fever
- Pain at the side of the body
What causes acute cortical necrosis in new-borns?
In newborns, more than half of the cases occur after delivery complicated by premature detachment of the placenta. The next most common cause is a bacterial infection of the bloodstream (sepsis).
What is the most common cause of acute cortical necrosis in children?
In children, renal cortical necrosis may occur after severe infection, severe dehydration, shock, or the hemolytic-uremic syndrome.
What is the most common cause of acute cortical necrosis in women?
In women, about half of the cases occur after complications of pregnancy, such as premature detachment of the placenta or abnormal position of the placenta, bleeding from the uterus, infections immediately after childbirth, blockage of arteries by amniotic fluid, death of the fetus within the uterus, and preeclampsia.
What are the most common causes of acute cortical necrosis in adults?
Other causes in adults include severe infection, blood loss after injuries, rejection of a transplanted kidney, burns, inflammation of the pancreas (pancreatitis), snakebite, use of certain drugs, and poisoning caused by certain chemicals.
What is contrast nephropathy?
iodinated radiological contrast media can be nephrotoxic by causing renal vasoconstriction and by exerting a direct toxic effect on tubules
What is acute phosphate nephropathy?
where calcium phosphate deposits form in the kidneys due to sodium phosphate solution give for bowel preparations for GI investigations
Describe how tumour lysis syndrome can cause AKI:
chemotherapy causes rapid cell death of malignant cells, stimulating the release of intracellular and membrane products including uric acid, potassium and phosphate - the uric acid can lead to crystal uropathy
Name 3 products of tumour lysis syndrome:
- Uric acid
- Potassium
- Phosphate
Name a drug that can reduce to nephrotoxic effects of tumour lysis syndrome:
Rasburicase
Describe how rasburicase can reduce the nephrotoxic effects of tumour lysis syndrome:
it uses urase oxidase to oxidise uric acid
Describe how hepatorenal syndrome can cause AKI:
portal hypertension can cause profound renal vasoconstriction (while the kidneys remain histologically normal)
