What is the diagnosis and next steps for a patient with impaired renal function, indicated by elevated creatinine levels, while being treated with vancomycin?

Differential Diagnosis

The patient's elevated creatinine level, from 0.78 to 2.13 mg/dL, in the context of vancomycin treatment, suggests a renal issue. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis
  • Vancomycin-induced nephrotoxicity: This is a well-documented side effect of vancomycin, especially with elevated trough levels. The rapid increase in creatinine levels after starting vancomycin supports this diagnosis.
• Other Likely Diagnoses
  • Pre-renal acute kidney injury (AKI): Dehydration or decreased blood flow to the kidneys could cause a rise in creatinine. However, there's no clear indication of dehydration or hypovolemia in the provided information.
  • Post-renal AKI: Obstruction of the urinary tract could cause AKI, but there's no mention of symptoms or findings suggestive of obstruction.
• Do Not Miss Diagnoses
  • Rhabdomyolysis: Although less likely, rhabdomyolysis can cause a rapid increase in creatinine and is a medical emergency. It would be crucial to check for muscle pain, dark urine, and elevated CPK levels.
  • Contrast-induced nephropathy: If the patient has undergone any imaging studies with contrast recently, this could be a consideration, although the timing and context are not provided.
• Rare Diagnoses
  • Acute interstitial nephritis (AIN): This is an inflammatory condition that can be caused by medications, including antibiotics. While vancomycin is more commonly associated with nephrotoxicity, AIN is a possibility, especially if the patient has been exposed to other medications.
  • Vasculitis or glomerulonephritis: These are less common causes of AKI and would typically be associated with other systemic symptoms or findings, such as hematuria or proteinuria, which are not mentioned in the provided information.

Given the context of vancomycin treatment and the rapid rise in creatinine, vancomycin-induced nephrotoxicity is the most likely diagnosis. However, it's essential to consider other potential causes, especially those that could be rapidly progressive or have significant morbidity if missed.