What is the workup for Impaired renal function (Renal Insufficiency)?

From the Guidelines

A renal insufficiency work-up should begin with a comprehensive metabolic panel, including serum creatinine, blood urea nitrogen (BUN), and electrolytes, and calculate the estimated glomerular filtration rate (eGFR) using the CKD-EPI equation, as recommended by the most recent guidelines 1. The work-up should also include:

• A complete blood count to assess for anemia
• Urinalysis with microscopy to look for proteinuria, hematuria, and casts
• Measure urine protein-to-creatinine ratio to quantify proteinuria
• If acute kidney injury is suspected, compare current lab values to baseline and repeat tests within 24-48 hours
• For chronic kidney disease evaluation, include tests for secondary hyperparathyroidism (intact PTH, calcium, phosphorus) and vitamin D levels Renal ultrasound should be performed to assess kidney size, echogenicity, and rule out obstruction. Additional imaging such as CT or MRI may be necessary depending on findings. Further specialized tests may include:
• Autoimmune markers (ANA, ANCA, anti-GBM antibodies)
• Complement levels
• Serum and urine protein electrophoresis
• Hepatitis B and C serologies A kidney biopsy may be indicated if the cause remains unclear or if specific diagnoses like glomerulonephritis are suspected, as suggested by the KDIGO practice guideline on glomerulonephritis 1. This comprehensive approach allows for the identification of the underlying cause of renal insufficiency, assessment of its severity, and guides appropriate management strategies, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Diagnostic Evaluation

The workup for impaired renal function (renal insufficiency) involves a thorough investigation, including:

• 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 3, 4, 2, 5
  • Complete blood count 2
  • Urinalysis 2
  • Fractional excretion of sodium 2
• Ultrasonography of the kidneys to rule out obstruction, particularly in older men 2
• Calculation or measurement of creatinine clearance to assess the severity of renal insufficiency 4

Classification and Management

Renal failure can be classified as acute or chronic, with different diagnostic and therapeutic consequences:

• Acute kidney injury (AKI) is characterized by abrupt deterioration in kidney function, and its management involves fluid resuscitation, avoidance of nephrotoxic medications, and correction of electrolyte imbalances 2
• Chronic renal failure is often progressive, and its management involves treating high blood pressure, proteinuria, and hyperlipidemia, as well as avoiding dehydration and certain medications or toxic substances 4
• Referral to a nephrologist is recommended for patients with chronic renal insufficiency, particularly when creatinine clearance falls below 50 ml/min or when symptoms occur 4

Biomarkers and Monitoring

Various biomarkers can be used to assess renal function and detect kidney disease, including:

• Serum creatinine (SCr) and creatinine-based estimating equations, which have limitations in certain situations 5
• Novel biomarkers, such as KIM-1, NGAL, and cycle arrest biomarkers, which have the potential to identify patients with AKI and CKD earlier and improve outcomes 5
• Combinations of biomarkers, such as NGAL, cystatin C, and FGF-23, which can increase diagnostic accuracy and improve risk stratification for kidney disease progression and mortality 5