AKIN Classification for Acute Kidney Injury (AKI)
Classifies severity of acute kidney injury, similar to RIFLE Criteria.
Patients on renal replacement therapy (RRT) are considered to be stage 3 regardless of whether they meet formal criteria.
Causes of elevations in creatinine can be grouped into three categories:
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Prerenal:
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Not all elevations in creatinine represent actual injury to cells within the kidneys.
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Volume depletion (or effective arterial volume depletion) results in a need to retain sodium and other solutes at the level of the tubule to help support blood pressure.
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This can be marked by the presence of a low fractional excretion of sodium and can be effectively treated with volume expansion.
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While this is often called AKI, it is technically a physiologic response to decreased renal perfusion.
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Intrarenal:
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Intrarenal causes of acute kidney injury include damage to the glomeruli (glomerulopathies) or tubules (acute tubular necrosis or allergic interstitial nephritis).
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Next steps should include examining the urine to try to determine the location of the injury within the nephron.
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Postrenal: Postrenal causes are generally due to obstruction to urine flow at the level of the ureters, bladder, or urethra.
- The management of AKI is both supportive and focused on etiology.
- While a kidney biopsy is frequently not needed to determine the cause of AKI, it can provide essential information, particularly if a glomerulopathy is suspected as the cause.
- Management should focus on identifying the cause of kidney injury, determining the need for a kidney biopsy, and reversing all contributing factors to prevent further loss of kidney function.
- Clinical actions may include correcting volume depletion or hypotension and avoiding medications that can contribute to further kidney injury.