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Acute kidney injury: Difference between revisions
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'''Acute kidney injury''' (AKI) is a clinical syndrome which is characterised by an acute decrease kidney function (<abbr>[[Glomerular filtration rate|GFR]])</abbr> (over hours or days), as evidenced by elevated creatinine. There may also be accumulation of urinary waste products and [[Oliguria and anuria|oliguria/anuria]], but not always. The cause may be prerenal, renal, or postrenal, but the most common causes are prerenal and [[acute tubular necrosis]]. | <section begin="radiology" />'''Acute kidney injury''' (AKI) is a clinical syndrome which is characterised by an acute decrease kidney function (<abbr>[[Glomerular filtration rate|GFR]])</abbr> (over hours or days), as evidenced by elevated creatinine. There may also be accumulation of urinary waste products and [[Oliguria and anuria|oliguria/anuria]], but not always. The cause may be prerenal, renal, or postrenal, but the most common causes are prerenal and [[acute tubular necrosis]]. | ||
During the evaluation it’s important to determine whether it’s really acute or chronic, and to determine the underlying cause. Management includes treating the cause and correcting severe electrolyte disturbances. In some cases, [[renal replacement therapy]] may be required. | During the evaluation it’s important to determine whether it’s really acute or chronic, and to determine the underlying cause. Management includes treating the cause and correcting severe electrolyte disturbances. In some cases, [[renal replacement therapy]] may be required. | ||
The condition is nowadays called acute kidney injury rather than '''acute renal failure'''. | The condition is nowadays called acute kidney injury rather than '''acute renal failure'''.<section end="radiology" /> | ||
== Etiology == | == Etiology == | ||
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== Clinical features == | == Clinical features == | ||
[[Oliguria and anuria|Oliguria]] is the most common symptom, but in many cases it’s asymptomatic. There may be symptoms of the underlying cause, or symptoms of [[uraemia]]. | [[Oliguria and anuria|Oliguria]] is the most common symptom, but in many cases it’s asymptomatic. There may be symptoms of the underlying cause, or symptoms of [[uraemia]]. | ||
<section begin="radiology" /> | |||
== Diagnosis and evaluation == | == Diagnosis and evaluation == | ||
<section end="radiology" />In the evaluation of AKI, the estimated [[Glomerular filtration rate|GFR]] (eGFR) can ''not'' be used to evaluate the kidney function, as it's estimated according to formulas which are made for chronic kidney disease. The serum [[creatinine]] must be used instead (''normal range 60 – 100 µmol/L)''. AKI is the only condition in which we use serum creatinine to monitor kidney function rather than eGFR. | |||
In the evaluation of AKI, the estimated [[Glomerular filtration rate|GFR]] (eGFR) can ''not'' be used to evaluate the kidney function, as it's estimated according to formulas which are made for chronic kidney disease. The serum [[creatinine]] must be used instead. AKI is the only condition in which we use serum creatinine to monitor kidney function rather than eGFR. | |||
During the evaluation of a person with acute kidney injury, it’s important to answer these 5 questions: | During the evaluation of a person with acute kidney injury, it’s important to answer these 5 questions: | ||
* Is it really AKI, or is it CKD or acute-on-chronic? | * Is it really AKI, or is it CKD or acute-on-chronic? | ||
** Is this really an acute loss of kidney function or is this a | ** Is this really an acute loss of kidney function or is this a newly discovered CKD? | ||
** Did the patient already have decreased GFR and this is just a worsening? | ** Did the patient already have decreased GFR and this is just a worsening? | ||
* Is there a prerenal cause? | * Is there a prerenal cause? | ||
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Patient history, physical examination, previous [[kidney function tests]], and [[ultrasound]] can help answer these questions. An AKI kidney has normal morphology, as opposed to a CKD kidney. A renal cause usually has abnormal [[urine analysis]]. A postrenal cause can have a palpable bladder, or obstruction or pyelectasis can be visible on US. Allergic symptoms can suggest nephritis. Low BP can suggest hypovolaemia. | Patient history, physical examination, previous [[kidney function tests]], and [[ultrasound]] can help answer these questions. An AKI kidney has normal morphology, as opposed to a CKD kidney. A renal cause usually has abnormal [[urine analysis]]. A postrenal cause can have a palpable bladder, or obstruction or pyelectasis can be visible on US. Allergic symptoms can suggest nephritis. Low BP can suggest hypovolaemia. | ||
<section begin="radiology" /> | |||
In case of AKI, the kidney is usually enlarged, which can be visualised on ultrasonography. Ultrasound may also reveal an underlying cause and is therefore usually the first choice imaging modality for AKI. | |||
<section end="radiology" /> | |||
The urea:creatinine ratio may be useful in finding the cause. A high ratio (> 20:1) suggests a prerenal cause, while a lower ratio (< 20:1) suggests a renal cause. | The urea:creatinine ratio may be useful in finding the cause. A high ratio (> 20:1) suggests a prerenal cause, while a lower ratio (< 20:1) suggests a renal cause. | ||