What is the initial workup for acute renal failure?

From the Guidelines

The initial workup for acute renal failure should begin with a thorough history, physical examination, and laboratory analysis of blood and urine, including serum creatinine, blood urea nitrogen, complete blood count, and differential, as well as urine microscopy for casts and epithelial cells, chemistry, and biomarkers 1. The diagnosis of acute kidney injury (AKI) is defined as an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline (within prior 7 days) or urine volume 0.5 mL/kg/hr for 6 hours 1. Key components of the initial workup include:

• Serum creatinine and blood urea nitrogen to assess the severity of renal impairment
• Urinalysis with microscopic examination to identify casts, epithelial cells, and other abnormalities
• Complete blood count and differential to evaluate for potential causes of AKI, such as infection or inflammation
• Calculation of the fractional excretion of sodium (FENa) to help differentiate between prerenal, intrinsic, and postrenal causes
• Renal ultrasound to rule out obstruction and assess kidney size and echogenicity
• Medication review to identify nephrotoxic agents that should be discontinued
• Volume status assessment to guide fluid management decisions It is essential to identify the specific cause of AKI, as there are different treatments for diseases such as glomerulonephritis, vasculitis, and ureteral obstruction 1. The evaluation of the patient with AKI should be tailored to the individual's clinical presentation and suspected underlying cause, with additional tests and imaging studies ordered as needed to guide management and treatment.

From the Research

Initial Workup for Acute Renal Failure

The initial workup for acute renal failure involves a comprehensive approach to identify the underlying cause and assess the severity of the condition. The following steps are recommended:

• 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
  • Complete blood count 2
  • Urinalysis 2, 4
  • Fractional excretion of sodium 2, 4
• Ultrasonography of the kidneys to rule out obstruction, particularly in older men 2

Classification of Acute Kidney Injury

Acute kidney injury can be classified into three categories:

• Prerenal: caused by poor renal perfusion or decreased blood flow to the kidneys 2, 3, 4
• Intrinsic renal: caused by direct damage to the kidneys 2, 3, 4
• Postrenal: caused by obstruction of the urinary tract 2, 3, 4

Management of Acute Renal Failure

The management of acute renal failure involves:

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