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Acute kidney injury: Difference between revisions
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<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]]. | <section begin="clinical biochemistry" /><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]]. <section end="clinical biochemistry" /> | ||
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'''.<section end="radiology" /> | The condition is nowadays called acute kidney injury rather than '''acute renal failure'''.<section end="radiology" /><section begin="clinical biochemistry" /> | ||
== Etiology == | == Etiology == | ||
AKI is classified according to the underlying cause, whether it’s a prerenal cause, a renal cause, or a postrenal cause. However, there are usually multiple factors involved. | AKI is classified according to the underlying cause, whether it’s a prerenal cause, a renal cause, or a postrenal cause. However, there are usually multiple factors involved. | ||
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** [[Prostate cancer]] | ** [[Prostate cancer]] | ||
** [[Gynaecological cancer]] | ** [[Gynaecological cancer]] | ||
<section end="clinical biochemistry" />Of these, the prerenal causes are the most common, followed by acute tubular necrosis. | |||
Of these, the prerenal causes are the most common, followed by acute tubular necrosis. | |||
Drugs which can cause AKI (by various mechanisms) are most commonly [[Non-steroidal anti-inflammatory drugs|NSAIDs]] and [[Renin angiotensin aldosterone system inhibitors|RAAS inhibitors]]. | Drugs which can cause AKI (by various mechanisms) are most commonly [[Non-steroidal anti-inflammatory drugs|NSAIDs]] and [[Renin angiotensin aldosterone system inhibitors|RAAS inhibitors]]. | ||
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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" /><section begin="clinical biochemistry" /> | ||
<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 | <section end="radiology" />In the evaluation of AKI, we use serum [[creatinine]] as a marker of [[Kidney function tests|kidney function]] (''normal range 60 – 100 µmol/L)''; the estimated [[Glomerular filtration rate|GFR]] (eGFR) can ''not'' be used, as it's estimated according to formulas which are made for chronic kidney disease. The definition of AKI requires either (1) an increase in serum creatinine by 27 µmol/L, or (2) an increase to more than 150% of baseline serum creatinine over 48 hours, or (3) a decrease in urine volume to < 3 mL/kg over 6 hours.<section end="clinical biochemistry" /> | ||
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 newly discovered CKD? | ** 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? | ||
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* Is there a renoparenchymal disease? | * Is there a renoparenchymal disease? | ||
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 | Patient history, physical examination, previous [[kidney function tests]], and [[ultrasound]] can help answer these questions. An AKI kidney has normal macroscopic morphology, as opposed to a CKD kidney. A renal cause usually has abnormal [[urine analysis]], with proteinuria, increased urinary sodium, or decreased urinary osmolality. A postrenal cause can have a palpable bladder, or obstruction or hydronephrosis can be visible on [[ultrasonography]]. 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 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. | <section end="radiology" /><section begin="clinical biochemistry" />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.<section end="clinical biochemistry" /> | ||
If the cause remains unclear despite these investigations, a [[renal biopsy]] may be required. | If the cause remains unclear despite these investigations, a [[renal biopsy]] may be required. | ||