Differential Diagnosis for Acute Kidney Injury
The patient presents with acute kidney injury (AKI) 48 hours after being hospitalized for herpes simplex virus encephalitis and starting treatment with intravenous high-dose acyclovir. Given the clinical context, the differential diagnoses can be categorized as follows:
Single Most Likely Diagnosis
- D. Intratubular Obstruction: This is likely due to acyclovir crystalluria, given that the patient is on high-dose intravenous acyclovir. The presence of fine-needle crystals in the urinalysis supports this diagnosis. Acyclovir can precipitate in the renal tubules, especially in a dehydrated state or with high doses, leading to intratubular obstruction and AKI.
Other Likely Diagnoses
- B. Acute Interstitial Nephritis: Although less likely than intratubular obstruction due to acyclovir, acute interstitial nephritis (AIN) could be considered, especially if the patient had been exposed to other medications known to cause AIN, such as antibiotics (though they were discontinued) or NSAIDs (not mentioned). However, the absence of eosinophilia and the specific context of acyclovir use make this less probable.
- C. Acute Tubular Necrosis: This could be a consideration, especially if there were issues with hypotension, sepsis, or nephrotoxic agents. However, the patient's vital signs are normal, and there's no clear indication of sepsis or recent hypotension that would typically precede ATN.
Do Not Miss Diagnoses
- A. Acute Glomerulonephritis: Although less likely given the clinical context, acute glomerulonephritis should not be missed as it can have serious implications. The presence of hematuria and proteinuria could suggest glomerular disease, but in the context of hereditary nephritis and the current clinical scenario, it's less likely to be the acute cause of AKI.
Rare Diagnoses
- Other rare causes of AKI, such as vasculitis or thrombotic microangiopathy, are not strongly suggested by the clinical presentation or laboratory findings in this case. The patient's history and current treatment provide a more straightforward explanation for the AKI, making these rare diagnoses less likely.