What is the initial approach to evaluate and manage Acute Kidney Injury (AKI) with an unknown cause?

From the Guidelines

The initial approach to evaluating and managing acute kidney injury (AKI) of unknown cause involves a systematic assessment starting with a thorough history and physical examination, followed by laboratory and imaging studies, with a focus on discontinuing potentially nephrotoxic medications and optimizing hemodynamics. This approach is crucial in preventing further kidney damage and managing complications until the definitive treatment can be initiated. According to 1, evaluating nephrotoxins as a plausible cause of AKI is the first consideration in the management of medications for patients with AKI, and determining nephrotoxic causality involves assessment of the temporal sequence between administration and the onset of injury.

Key Steps in Evaluation and Management

• Obtain baseline renal function values including serum creatinine, blood urea nitrogen (BUN), and electrolytes, along with a urinalysis and urine microscopy to look for casts, cells, or crystals.
• Calculate the fractional excretion of sodium (FENa) to help distinguish between prerenal, intrinsic, and postrenal causes.
• Order a renal ultrasound promptly to rule out obstruction, which requires immediate intervention.
• Discontinue all potentially nephrotoxic medications including NSAIDs, aminoglycosides, contrast agents, and adjust medication dosages based on estimated GFR.
• Optimize hemodynamics by ensuring adequate hydration with isotonic fluids, but avoid volume overload.
• Monitor urine output (target >0.5 mL/kg/hr) and daily weights.
• Check for acid-base disturbances and electrolyte abnormalities, particularly hyperkalemia, which may require urgent treatment.

As recommended by 1, evaluating patients with AKI promptly to determine the cause, with special attention to reversible causes, is essential. By following this systematic approach, healthcare providers can identify the underlying cause of AKI, prevent further kidney damage, and manage complications effectively, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Initial Approach to Evaluate and Manage AKI with Unknown Cause

The initial approach to evaluate and manage Acute Kidney Injury (AKI) with an unknown cause involves a thorough history and physical examination to categorize the underlying cause as prerenal, intrinsic renal, or postrenal 2.

Key Components of Initial Evaluation

• Assessment of contributing causes of the kidney injury 3
• Assessment of the clinical course including comorbidities 3
• Careful assessment of volume status 3
• Institution of appropriate therapeutic measures designed to reverse or prevent worsening of functional or structural kidney abnormalities 3
• Laboratory work-up, including measurement of serum creatinine level, complete blood count, urinalysis, and fractional excretion of sodium 4
• Ultrasonography of the kidneys to rule out obstruction, particularly in older men 4

Management of AKI

• Fluid resuscitation 4
• Avoidance of nephrotoxic medications and contrast media exposure 4
• Correction of electrolyte imbalances 4
• Renal replacement therapy (dialysis) for refractory hyperkalemia, volume overload, intractable acidosis, uremic encephalopathy, pericarditis, or pleuritis, and removal of certain toxins 4

Importance of Early Determination of Etiology

Early determination of etiology, management, and long-term follow-up of AKI are essential, as even one episode of AKI increases the risk of cardiovascular disease, chronic kidney disease, and death 2. Recognition of risk factors, such as older age, sepsis, hypovolemia/shock, cardiac surgery, infusion of contrast agents, diabetes mellitus, preexisting chronic kidney disease, cardiac failure, and liver failure, is also important 4.