Renal - Acute Kidney Injury Flashcards
What is the definition of acute kidney injury?
An acute drop in kidney funciton from the patient’s baseline of normal.
How is AKI diagnosed?
By measuring the patient’s serum creatinine
What is the NICE criteria for AKI?
Urine output of <0.5ml/kg/hour for over 6 hours
Rise in creatinine of >50% in 7 days OR rise in creatinine of >25 micromol/L in 48 hours
List some risk factors for developing an AKI
Nephrotoxic medications Heart failure Liver disease Dehydration Sepsis Old age CKD Diabetes Contrast medium in CTs Cognitive impairment
How can we differentiate the causes of Acute Kidney injury?
They will either be
Pre-renal
Renal
Post Renal
What is the most common form of AKI
Pre renal
How does pre renal AKI occurt?
There is reduced perfusion of the kidneys due to an inadequate blood supply
List the main causes of pre-renal AKI
Dehydration
Hypotension / shock
Heart failure
(Renal artery stenosis)
Define Renal AKI:
The intrinsic disease in the kidneys has led to a reduced filtration of blood
What are the causes of a renal AKI?
Glomerulonephritis
Acute Tubular necrosis
Interstitial nephritis
Describe the physiology of how a post renal AKI occurs?
There is an obstruction to the outflow from the kidney which leads to a back pressure into the kidney, reducing the kidney function.
AKA obstructive uropathy
List some causes of post renal AKI:
Kidney stones
Ureter strictures
Masses such as cancer in abdo
ENlarged prostate / prostate cancer
What investigation should be done if you cannot find the source of the post renal AKI?
USS of the urinary tract to source the blockage
What are some complications of an AKI?
Hyperkalemia
Fluid overload - from management
Metabolic Acidosis
Uraemia –> leading to encephalopathy and / or pericarditis
If protein and blood are found in the urinalysis what could be the cause of the AKI?
Acute nephritis
or infection
Give some examples of illnesses which can lead to/ make you more vulnerable to, acute tubular necrosis?
Cholestatic jaundice DIC Liver failure Pregnancy Pancreatitis
What are some acute features of acute tubular necrosis?
uraemia symptoms: Anorexia Vomiting Pruritis Drowsiness Fits Nausea Epistaxis
Define Acute tubular necrosis:
Damage and death of the epithelial cells of the renal tubules.
Acute tubular necrosis is reversible - true or false?
True
The epithelial cells have the ability to regenerate
How long does it usually take to recover from AKI with acute tubular encroiss?
7 - 21 days
Rhabdomyolysis is a form of ____ AKI?
Renal
List some toxins which can cause acute tubular necrosis:
Gentamicin NSAIDs Lithium Heroin Radiology contrast dye
What is a pathognomonic finding on urinalysis, specific to acute tubular necrosis?
Muddy brown casts
Renal tubular epithelial cells in the urine
In Acute Tubular necrosis, what 3 things will be raised on biochemistry?
Urea
Potassium
Phosphate
In acute tubular necrosis, what 3 things will be low on biochemistry?
pH
Calcium
Sodium
In acute tubular necrosis what part of the kidney specifically is blood flow reduced?
Renal cortex
What is the main symptom of an AKI resulting from acute tubular necrosis?
Oliguria (reduced urine output)
Acute tubular necrosis resolves spontaneously. True or false?
True
The main aims of management is preventing uraemia hyperkalaemia etc and reducing sepsis risks.
What is a severe outcome of acute tubular necrosis if it does not resolve quickly?
Cortical necrosis
Caused by reduced blood flow to the renal cortex, and instead of regenerating it heals via scarring (glomerulosclerosis) and eventually necrosis.
In an AKI what would be indicators for management with dialysis?
Pulmonary oedema
Persistent hyperkalemia despite intervention
Severe metabolic acidosis
Uraemic pericarditis / encephalopathy etc
Drug overdose (to remove drug)
List some medications which must be stopped in an AKI as they may worsen the renal funciton?
NSAIDs ACE inhibitors ARBs Aminoglycosides Diuretics
In hyperkalemia, which drug is given for cardiac stabilization purposes?
Calcium gluconate IV
How does insulin and dextrose infusion, and sometimes nebulised salbutamol, help in the management of hyperkalemia?
It temporarily reduces the k+ by shifting it from the extracellular to the intracellular compartments.
What medications can be given in hyperkalemia to reduce the potassium levels by removing them from the body?
Calcium resonium (orally or enema)
(Loop diuretics - use with caution)
Dialysis
Give some examples of medications which are suitable to continue in an AKI?
Warfarin Aspirin (at a cardioprotective dose) Paracetamol Statins Clopidogrel
Give some examples of medications that are nephrotoxic but do not worsen AKI so can be stopped or continued during an AKI?
Lithium
Digoxin
Metformin
What would brown granular casts in the urine be suggestive of?
renal AKI from Acute tubular necrosis
How can you differentiate between a pre renal and renal cause of an AKI?
Fluid challenge
If they respond well the cause is probably pre renal
In acute tubular necrosis, the serum urea:creatinine ratio will be normal. True or false?
True
In pre renal causes the ratio will be higher
In a Renal AKI, will the urine osmolality be high or low?
Low
roughly <350 mOsm/kg
In acute tubular necrosis the urine concentration of sodium will be low. True or false?
False
high excretion of sodium is suggestive of an impaired exchange at the tubule which indicates acute tubular necrosis
