Differential Diagnosis for Increased Osmol Gap
Single Most Likely Diagnosis
- Ethanol intoxication: This is often the most common cause of an increased osmol gap due to the high osmolality of ethanol. Ethanol is a common substance that can cause significant alterations in mental status and can be easily measured in the laboratory.
Other Likely Diagnoses
- Other alcohols (e.g., methanol, isopropanol, ethylene glycol): Like ethanol, these substances can significantly increase the osmol gap. They are less common causes than ethanol but are critical to identify due to their potential for severe toxicity.
- Diabetic ketoacidosis: Although the primary issue in diabetic ketoacidosis is the production of ketone bodies, which can increase the anion gap, the osmol gap can also be elevated due to the hyperglycemia.
- Hypertriglyceridemia: Extremely high levels of triglycerides can increase the osmol gap, although this is less common and usually seen in the context of other significant laboratory abnormalities.
Do Not Miss Diagnoses
- Methanol or ethylene glycol poisoning: These are critical to identify because they can cause severe and irreversible damage (e.g., blindness from methanol, renal failure from ethylene glycol) if not promptly treated with specific antidotes like fomepizole or hemodialysis.
- Isopropanol intoxication: Isopropanol has a higher osmolality than ethanol and can cause more severe CNS depression and other systemic effects, making prompt recognition and treatment crucial.
Rare Diagnoses
- Sorbitol: Used in some medical products and as a sugar substitute, sorbitol can increase the osmol gap, especially in the context of diabetic emergencies or when used in large quantities.
- Mannitol: This is an osmotic diuretic used in certain medical conditions. It can increase the osmol gap, particularly if there's impaired renal function leading to its accumulation.
- Glycerol: Elevated levels, such as those seen in certain metabolic disorders or with ingestion of large amounts, can contribute to an increased osmol gap.
- Propylene glycol: Used as a solvent in some pharmaceuticals (e.g., certain anticonvulsants), propylene glycol can accumulate and increase the osmol gap, especially in patients with renal impairment or those receiving high doses of medications containing this solvent.