Differential Diagnosis for Hyperchloremic Metabolic Acidosis
- The following differential diagnosis is organized into categories to help guide the diagnostic process.
Single Most Likely Diagnosis
- Gastrointestinal Bicarbonate Loss: This is the most common cause of hyperchloremic metabolic acidosis, often due to severe diarrhea, where bicarbonate is lost in the stool, and chloride is exchanged to maintain electroneutrality.
Other Likely Diagnoses
- Renal Tubular Acidosis (RTA): Specifically, types 1 and 2, where the kidney fails to appropriately reboarm (reabsorb bicarbonate) or secrete hydrogen ions, leading to a loss of bicarbonate and a high chloride level.
- Diarrhea-induced Acidosis: Similar to gastrointestinal bicarbonate loss, but can be due to various causes of diarrhea, including infections, medications, or malabsorption syndromes.
- Amphetamine or Methamphetamine Intoxication: Certain drugs can cause a hyperchloremic metabolic acidosis by increasing chloride reabsorption in the kidneys.
Do Not Miss Diagnoses
- Lactic Acidosis: Although lactic acidosis typically presents with an increased anion gap, it can occasionally present as a hyperchloremic metabolic acidosis, especially if there is a concomitant loss of bicarbonate. Missing this diagnosis can be fatal.
- Salicylate Toxicity: Similar to lactic acidosis, salicylate toxicity can present with a mixed anion gap and non-anion gap (hyperchloremic) metabolic acidosis. It is crucial to identify and treat promptly.
- Ethylene Glycol or Methanol Poisoning: These can initially present with a high anion gap metabolic acidosis but can evolve into a hyperchloremic metabolic acidosis as the toxic alcohols are metabolized. Early recognition is critical for effective treatment.
Rare Diagnoses
- Chloride-rich Intravenous Fluids: Administration of large volumes of chloride-rich IV fluids, such as 0.9% saline, can lead to hyperchloremic metabolic acidosis, especially in patients with limited ability to exone (excrete) chloride.
- Bariatric Surgery: Certain types of bariatric surgery can lead to malabsorption of bicarbonate and an increased excretion of chloride, resulting in hyperchloremic metabolic acidosis.
- Topiramate-induced Acidosis: Topiramate, an antiepileptic drug, can cause a hyperchloremic metabolic acidosis by inhibiting carbonic anhydrase in the kidney, leading to bicarbonate loss.