Differential Diagnosis for Confusion and Metabolic Acidosis in a 77yo Female
Single Most Likely Diagnosis
- Sepsis: Given the patient's age and presentation with confusion and metabolic acidosis, sepsis is a highly plausible diagnosis. The absence of abnormal U&Es, FBC, LFTs, and a normal CT head does not rule out sepsis, as it can present subtly in the elderly.
Other Likely Diagnoses
- Diabetic Ketoacidosis (DKA): Although the patient's U&Es are reported as nil acute, it's essential to check the blood glucose level to rule out DKA, especially since metabolic acidosis is a key feature.
- Lactic Acidosis: This could be due to various causes, including medication (e.g., metformin in the context of CKD), poor perfusion, or sepsis. Given the patient's CKD stage 3, metformin-induced lactic acidosis is a consideration if she is on this medication.
- Uremic Encephalopathy: Although the patient has CKD stage 3, significant metabolic disturbances can still occur, potentially leading to uremic encephalopathy, which could explain the confusion.
Do Not Miss Diagnoses
- Meningitis/Encephalitis: Despite a normal CT head, these diagnoses can present with non-specific symptoms in the elderly, including confusion. A lumbar puncture may be necessary to rule out these conditions.
- Carbon Monoxide Poisoning: This can cause confusion and metabolic acidosis without specific findings on initial laboratory tests or imaging. It's crucial to consider environmental exposures.
- Salicylate Toxicity: Aspirin overdose can lead to metabolic acidosis and altered mental status. It's vital to inquire about medication use and consider a salicylate level.
Rare Diagnoses
- Ethylene Glycol or Methanol Poisoning: These can cause metabolic acidosis and neurological symptoms. Although less common, they are critical to consider due to their potential for severe outcomes if not promptly treated.
- Mitochondrial Disorders: In rare cases, mitochondrial myopathies can present with lactic acidosis and neurological symptoms. This would be more unusual in a new presentation at the age of 77 but could be considered if other diagnoses are ruled out.