From the Guidelines
The workup for acute kidney injury (AKI) should begin with a thorough history and physical examination, followed by basic laboratory tests including serum creatinine, blood urea nitrogen (BUN), electrolytes, urinalysis, and urine microscopy. Calculate the patient's baseline creatinine and determine the AKI stage using KDIGO criteria 1. Order a renal ultrasound to assess kidney size, hydronephrosis, and obstruction. Specific tests should include urine sodium, fractional excretion of sodium (FENa) or urea (FEUrea), urine protein-to-creatinine ratio, and complete blood count. If glomerulonephritis is suspected, obtain complement levels, anti-nuclear antibody, anti-neutrophil cytoplasmic antibody, and anti-glomerular basement membrane antibody. For suspected rhabdomyolysis, check creatine kinase levels. Consider nephrology consultation for severe AKI (stage 3), rapidly worsening kidney function, or unclear etiology. The workup aims to differentiate between prerenal (volume depletion, heart failure), intrinsic renal (acute tubular necrosis, glomerulonephritis), and postrenal (obstruction) causes, as management differs significantly based on etiology. Review medication history carefully to identify nephrotoxic agents that should be discontinued, and adjust medication dosages according to the reduced kidney function, as recommended by the KDIGO guidelines 1.
Key considerations in the workup of AKI include:
- Discontinuing all nephrotoxic agents when possible 1
- Ensuring volume status and perfusion pressure 1
- Monitoring serum creatinine and urine output 1
- Avoiding hyperglycemia 1
- Considering alternatives to radiocontrast 1
- Checking for change in drug dosing 1
It is essential to note that the etiology of AKI is often multifactorial, and a thorough evaluation is necessary to determine the underlying cause, as stated in the ACR Appropriateness Criteria for renal failure 1. The workup for AKI should be guided by the KDIGO criteria, which provide a framework for the diagnosis, classification, and management of AKI 1. By following these guidelines, healthcare providers can ensure that patients with AKI receive timely and effective treatment, which can help to improve outcomes and reduce morbidity and mortality.
From the Research
Workup for Acute Kidney Injury (AKI)
The workup for AKI involves a comprehensive evaluation to determine the underlying cause and severity of the injury. 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:
- Ultrasonography of the kidneys to rule out obstruction, particularly in older men 2, 4
Classification of AKI
AKI can be classified into three categories:
- Prerenal: caused by decreased blood flow to the kidneys 2, 3, 5, 4
- Intrinsic renal: caused by damage to the kidneys themselves 2, 3, 5, 4
- Postrenal: caused by obstruction of the urinary tract 2, 3, 5, 4
Management of AKI
The management of AKI involves:
- Fluid resuscitation 2, 6, 4
- Avoidance of nephrotoxic medications and contrast media exposure 2, 4
- Correction of electrolyte imbalances 2, 6, 4
- Renal replacement therapy (dialysis) for refractory hyperkalemia, volume overload, intractable acidosis, uremic encephalopathy, pericarditis, or pleuritis, and removal of certain toxins 2, 6