From the Guidelines
The workup for acute kidney failure should involve a comprehensive approach, including a thorough history and physical examination, laboratory tests such as serum creatinine and blood urea nitrogen, urinalysis, and imaging studies like renal ultrasound, to identify the cause and guide treatment. This approach is crucial in distinguishing between prerenal, intrinsic, and postrenal causes of acute kidney injury (AKI), which is essential for targeted treatment strategies to prevent further kidney damage and promote recovery 1.
Key Components of the Workup
- A thorough history and physical examination to identify potential causes of AKI, such as medication use, recent illnesses, and signs of volume status.
- Laboratory tests, including:
- Serum creatinine and blood urea nitrogen to assess kidney function.
- Electrolytes, complete blood count, and urinalysis to identify potential electrolyte imbalances and signs of kidney damage.
- Urine studies, such as microscopic examination, protein quantification, and calculation of fractional excretion of sodium (FENa) to differentiate between prerenal, intrinsic, and postrenal causes.
- Imaging studies, such as renal ultrasound, to rule out obstruction and assess kidney size and structure.
- Additional tests, such as renal Doppler ultrasound to evaluate blood flow, and in some cases, a kidney biopsy may be necessary for definitive diagnosis of intrinsic kidney disease.
Diagnosis and Staging of AKI
The diagnosis of AKI is based on an increase in serum creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine output less than 0.5 mL/kg/h for 6 hours 1. The staging of AKI is based on the severity of the kidney injury, with stage 1 being the least severe and stage 3 being the most severe 1.
Importance of Early Detection and Treatment
Early detection and treatment of AKI are crucial in preventing further kidney damage and promoting recovery. Biomarkers like NGAL and KIM-1 can provide early detection of kidney injury, allowing for prompt intervention and treatment 1. A systematic approach to the workup and diagnosis of AKI is essential in identifying the cause and guiding treatment, ultimately improving patient outcomes and reducing morbidity and mortality.
From the Research
Diagnosis of Acute Kidney Failure
The diagnosis of acute kidney injury (AKI) is typically based on measurements of blood urea nitrogen (BUN) and serum creatinine 2. However, these markers are not very sensitive or specific for the diagnosis of AKI.
Diagnostic Criteria
The Kidney Disease: Improving Global Outcomes (KDIGO) defines AKI as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 3. The severity of AKI is determined by the degree of SCr increase or decrease in urine output.
Evaluation and Management
Evaluation of AKI begins with a careful review of the patient's history, physical examination, urinalysis, and available laboratory data 4. The history should focus on risk factors, including nephrotoxic drugs, and the physical examination should include determination of fluid volume status 3. Urinalysis with microscopy can narrow the differential diagnosis. Management of AKI includes control of the underlying cause, achievement and maintenance of euvolemia, nutritional optimization, blood glucose control, and pharmacotherapy 3, 5.
Key Considerations
- Accurate diagnosis of the underlying cause is key to successful management 5
- Determining the cause is critical when possible 3
- Nephrology consultation should be considered when there is inadequate response to supportive treatment and for AKI without a clear cause, stage 3 or higher AKI, preexisting stage 4 or higher chronic kidney disease, renal replacement therapy, and other situations requiring subspecialist expertise 3, 5
- Biomarkers of AKI, such as interleukin-18, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1, may aid in the diagnosis and prediction of long-term kidney outcomes and mortality 2, 6