Differential Diagnosis for Severe Metabolic Acidosis

Given the presence of severe metabolic acidosis, normal beta-hydroxybutyrate (BHB) levels, normal ethanol levels, acute kidney injury (AKI) without evidence of methanol or ethylene glycol poisoning, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis
  • Lactic acidosis: This is a common cause of severe metabolic acidosis, especially in the context of AKI. Lactic acidosis can result from tissue hypoxia, sepsis, or certain medications. The normal BHB and ethanol levels, along with the absence of methanol or ethylene glycol, make lactic acidosis a leading consideration.
• Other Likely Diagnoses
  • Diabetic ketoacidosis (DKA) with atypical presentation: Although BHB is normal, some cases of DKA may present with lower levels of ketones, especially if the patient has been treated with insulin or has a history of recurrent DKA. The presence of AKI could also complicate the typical presentation.
  • Salicylate toxicity: Aspirin overdose can cause severe metabolic acidosis. While it might not be the first consideration, it's a possibility, especially if there's a history of overdose or ingestion.
• Do Not Miss Diagnoses
  • Sepsis: Sepsis can lead to lactic acidosis and is a critical diagnosis to consider due to its high mortality rate if not promptly treated. The presence of AKI could be a complication of sepsis.
  • Ischemic bowel: This condition can cause lactic acidosis due to tissue hypoperfusion and is critical to identify early due to its high mortality rate.
• Rare Diagnoses
  • Pyroglutamic acidemia: A rare cause of metabolic acidosis, often associated with AKI and certain medications like acetaminophen.
  • Methylmalonic acidemia: A rare genetic disorder that can cause metabolic acidosis, though it's more commonly identified in pediatric patients.
  • Propionic acidemia: Another rare genetic disorder leading to metabolic acidosis, typically diagnosed in children but can be considered in adults with unexplained severe metabolic acidosis.

Each of these diagnoses requires careful consideration of the patient's clinical presentation, laboratory results, and medical history to determine the most appropriate diagnosis and treatment plan.