RENAL CONSULT / PEER REVIEWED

Acute Kidney Injury: Treatment Depends on the Cause

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Q)I have a patient with a discharge diagnosis of community-acquired acute kidney injury. What does this mean? What do I do now?

Acute kidney injury (AKI) refers to an abrupt decrease in kidney function that is possibly reversible or in which harm to the kidney can be modified.1,2 AKI encompasses a broad spectrum of conditions affecting the kidney—including acute renal failure, since even “failure” can sometimes be reversed.1 Criteria for AKI and its severity can be found in the Table.1

Defining Acute Kidney Injury

AKI can be either community-acquired (CA-AKI) or hospital-acquired (HA-AKI).1,2 In the United States, CA-AKI occurs less frequently than HA-AKI, although cases are likely underreported.1 Evaluation and management are similar for both.

The etiology of the AKI must be determined before treatment of the cause or precipitating factor can be attempted. Causes of AKI can be classified as prerenal (up to 70% of cases), intrinsic, or postrenal.1

Most AKI cases have a prerenal origin.3 Prerenal AKI occurs when there is inadequate blood flow to the kidneys, leading to a rise in blood urea nitrogen (BUN) and serum creatinine (SCr) levels. Reduced blood flow can be caused by

  • Diuretic dosing
  • Polypharmacy (diuretics, angiotensin-converting enzyme inhibitors [ACEIs]/ angiotensin receptor blockers [ARBs], and/or NSAIDs are common culprits)
  • Congestive heart failure exacerbation
  • Volume depletion through vomiting or diarrhea
  • Massive blood loss (trauma).3

Postrenal causes of AKI include any type of obstructive uropathy. Intrinsic causes involve any condition within the kidney, including interstitial nephritis or acute tubular necrosis. Use of antibiotics (eg, high-dose penicillin or vancomycin) is included in this category.

Obtaining an accurate medical history and examining the patient’s fluid status are critical. Although numerous novel biomarkers have been investigated for detection of AKI, none are yet in wide use. The primary assessment measures remain a serum panel to evaluate SCr and BUN levels; an electrolyte panel to assess for abnormalities; a complete blood count to assess for anemia caused by a less likely source; urinalysis; and imaging to assess for abnormalities or structural changes.

Urinalysis. Urine often holds the key to diagnosis of AKI. Notably in a prerenal injury, its specific gravity will be elevated, but the rest of the urine will likely be bland.3

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