What is the initial workup for a patient with Acute Kidney Injury (AKI)?

From the Guidelines

The initial workup for a patient with Acute Kidney Injury (AKI) should include a comprehensive history, physical examination, laboratory tests, and imaging studies, as outlined in the most recent guidelines 1. The workup should begin with obtaining a detailed medical history focusing on recent illnesses, medication use (especially nephrotoxic drugs like NSAIDs, aminoglycosides, or contrast agents), volume status changes, and symptoms of urinary obstruction.

• Physical examination should assess volume status, vital signs, and signs of systemic disease.
• Essential laboratory tests include serum creatinine and blood urea nitrogen (BUN) to confirm AKI and establish baseline renal function, complete blood count, comprehensive metabolic panel, and urinalysis with microscopy.
• Urine studies should include sodium, creatinine, protein, and osmolality to help differentiate between prerenal, intrinsic, and postrenal causes.
• Calculate the fractional excretion of sodium (FENa) to distinguish between prerenal disease (<1%) and acute tubular necrosis (>2%).
• Renal ultrasound is crucial to rule out obstruction and assess kidney size and echogenicity, as recommended by the American College of Radiology 1. Additional tests may include complement levels, antinuclear antibodies, and ANCA if glomerulonephritis is suspected, based on the clinical presentation and laboratory findings 1. This systematic approach helps determine the cause of AKI, which is essential for appropriate management and preventing further kidney damage, ultimately reducing morbidity, mortality, and improving quality of life.

From the Research

Initial Workup for Acute Kidney Injury (AKI)

The initial workup for a patient with Acute Kidney Injury (AKI) involves several key components:

• Patient history to identify the use of nephrotoxic medications or systemic illnesses that might cause poor renal perfusion or directly impair renal function 2
• Physical examination to assess intravascular volume status and identify skin rashes indicative of systemic illness 2
• Laboratory evaluation, including:
  • Measurement of serum creatinine level 2, 3, 4, 5, 6
  • Complete blood count 2
  • Urinalysis 2, 3
  • Fractional excretion of sodium 2
• Ultrasonography of the kidneys to rule out obstruction, particularly in older men 2 or as part of the diagnostic workup 5

Diagnostic Evaluation

The diagnostic evaluation can be used to classify AKI as prerenal, intrinsic renal, or postrenal 2. This classification is crucial for guiding management and treatment. The use of urine biochemical profile and microscopy can help identify the nature and site of kidney injury 3.

Importance of Early Detection

Early detection and management of AKI are critical for improving outcomes 2, 3, 5. The use of biomarkers, such as those discussed in 4, may help improve early diagnosis and guide treatment. 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 for preventing and managing AKI 2.