Differential Diagnosis for New AKI with Persistent HAGMA

Given the scenario of a patient with a new acute kidney injury (AKI) and persistent high anion gap metabolic acidosis (HAGMA) after an initial workup was negative, and an unremarkable urinalysis, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis
  • Lactic Acidosis: This is a common cause of HAGMA, especially in the context of AKI. Lactic acidosis can occur due to tissue hypoperfusion, sepsis, or as a side effect of certain medications. The new onset of AKI could exacerbate or contribute to the development of lactic acidosis.
• Other Likely Diagnoses
  • Diabetic Ketoacidosis (DKA): Although classic DKA presents with hyperglycemia, the presence of HAGMA and AKI could suggest a complicated or atypical presentation, especially if the patient has diabetes.
  • Ethylene Glycol or Methanol Poisoning: These toxic ingestions can cause HAGMA and AKI. The initial workup being negative does not rule out these possibilities if the ingestions were recent or if the tests were not specifically looking for these toxins.
  • Ketoacidosis due to Starvation or Alcohol: Similar to DKA, starvation or alcohol-induced ketoacidosis can present with HAGMA and could potentially lead to or worsen AKI.
• Do Not Miss Diagnoses
  • Sepsis: Sepsis can cause both HAGMA (through lactic acidosis) and AKI. It is crucial to consider and rule out sepsis due to its high mortality rate if left untreated.
  • Rhabdomyolysis: Although the urinalysis is unremarkable, rhabdomyolysis can cause AKI and sometimes contributes to HAGMA. It's a condition that requires prompt recognition and treatment.
• Rare Diagnoses
  • Pyroglutamic Acidemia: A rare cause of HAGMA, often associated with certain medications (like acetaminophen) or critical illness.
  • Isovaleric Acidemia or Other Organic Acidemias: These are rare genetic disorders that can cause HAGMA. They are more likely to be considered in patients with recurrent episodes of acidosis or in those with a family history of similar conditions.
  • Salicylate Toxicity: Aspirin overdose can cause HAGMA and AKI. Although less common, it is a critical diagnosis not to miss due to its potential for severe outcomes.

Each of these diagnoses requires careful consideration of the patient's clinical presentation, laboratory results, and history to determine the most appropriate next steps in management.