What is the initial workup for a patient presenting with acute renal failure?

From the Guidelines

The initial workup for a patient presenting with acute renal failure should include a comprehensive history, physical examination, laboratory tests, and imaging studies, as outlined in the 2021 study published in the Journal of the American College of Radiology 1. Begin by obtaining a detailed medical history focusing on potential causes such as medication use (especially NSAIDs, antibiotics, contrast agents), recent illnesses, changes in urination patterns, and pre-existing conditions like hypertension or diabetes. Physical examination should assess volume status, vital signs, and signs of systemic disease. Essential laboratory tests include:

• Serum creatinine
• Blood urea nitrogen (BUN)
• Electrolytes (sodium, potassium, calcium, phosphate)
• Complete blood count
• Urinalysis with microscopy Calculate the fractional excretion of sodium (FENa) to help distinguish between prerenal, intrinsic, and postrenal causes, as suggested by the Kidney Disease Improving Global Outcomes (KDIGO) guideline 1. A renal ultrasound should be performed to evaluate kidney size, echogenicity, and to rule out obstruction. Additional tests may include urine protein-to-creatinine ratio, complement levels, and autoimmune markers if glomerular disease is suspected. This comprehensive approach allows for rapid identification of the underlying cause, which is crucial for appropriate management as acute renal failure can quickly progress to permanent kidney damage if not addressed promptly. The KDIGO guideline provides a framework for the diagnosis and staging of acute kidney injury, including the use of creatinine and urine output criteria to classify the severity of AKI 1. By following this approach, clinicians can provide timely and effective care for patients with acute renal failure, improving outcomes and reducing the risk of long-term kidney damage. It is essential to note that the diagnosis and management of acute renal failure require a multidisciplinary approach, involving nephrologists, radiologists, and other healthcare professionals, as emphasized in the 2021 study published in the Journal of the American College of Radiology 1.

From the Research

Initial Workup for Acute Renal Failure

The initial workup for a patient presenting with acute renal failure involves a comprehensive approach to identify the underlying cause and guide management. This includes:

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

Diagnostic Classification

Acute renal failure can be classified as prerenal, intrinsic renal, or postrenal based on the diagnostic evaluation 2, 3, 5. This classification helps guide management and treatment.

Management

Management of acute renal failure involves:

• Fluid resuscitation 2, 5
• Avoidance of nephrotoxic medications and contrast media exposure 2, 5
• Correction of electrolyte imbalances 2, 5
• Renal replacement therapy (dialysis) for refractory hyperkalemia, volume overload, intractable acidosis, uremic encephalopathy, pericarditis, or pleuritis, and removal of certain toxins 2