The differential diagnosis for AKA is very broad. It is essentially the differential diagnosis of wide anion-gap metabolic acidosis. Lactic acidosis, uremia, and ingestants (particularly methanol and ethylene glycol) should be considered. A mild lactic acidosis is occasionally present in AKA related to ethanol metabolism, but it is comparatively inconsequential. A significant lactic acidosis always stems from another cause. Lactic acidosis related to anaerobic metabolism (e.g., hypotension, sepsis, or tissue ischemia) or associated with methanol, ethylene glycol, and salicylic acid are usually markedly more severe and less readily masked by concurrent metabolic alkalosis. Both salicylic acid poisoning and sepsis (related lactic acidosis) often present with triple acid-base disturbances (metabolic acidosis, metabolic alkalosis, and primary respiratory alkalosis). Renal failure as a potential etiology can be ascertained from the serum chemistries. Diabetic ketoacidosis has a blood sugar level greater than 300 mg/dL. Finally, a differentiation from starvation ketosis is an academic exercise and unimportant, because underlying pathophysiology, treatment, and implications are similar. Isopropyl alcohol ingestion results in production of ketones and is on occasion associated with a mild lactic acidosis on a similar basis as is found in AKA. The presence of an osmolal gap (which is also a feature of methanol and ethylene glycol poisoning) may be differentiating. However, ethanol is osmotically active and, if present, will also contribute to an osmolal gap. If the blood alcohol level is known, then its contribution to any osmolal gap can be calculated. If the entire osmolal gap cannot be attributed to the ethanol level, then isopropyl alcohol (mild or no acidosis), methanol, or ethylene glycol (severe acidosis) may well be the explanation. Each 100 mg/dL of ethanol raises the osmolal gap by 22. (A full discussion on the diagnostic approach to distinguish various wide anion-gap type acidosis is found in Chap 21, "Acid-Base Disorders." Details of osmolal gap are discussed in Chap,.,„23, "Fluids and Electrolyte Problems.")
Patients with AKA often have concurrent illnesses that may have promoted the alcohol cessation and anorexia. Thus, a thorough investigation for underlying illnesses should be performed. Common concurrent illnesses are pancreatitis, gastritis or upper gastrointestinal bleeding, seizures, alcohol withdrawal, sepsis, and hepatitis.
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