Urine Ketones Positive ≠ DKA

What Does Ketonuria Actually Mean?

• Brenner and Rector's The Kidney, 2-Volume Set, p. 1003: "Ketones may appear in the urine, but not in serum, with prolonged fasting or starvation. Ketones may also be detected in the urine in alcoholic or diabetic ketoacidosis."

What IS Required to Diagnose DKA?

• Goldman-Cecil Medicine International Edition: "The three fundamental biochemical features of diabetic ketoacidosis are hyperglycemia or a history of diabetes (the 'D'), urinary ketone levels of 2+ or more or 3.0 mmol/L or more (the 'K'), and an arterial or venous pH of less than 7.3 (the 'A')."
• The Washington Manual of Medical Therapeutics: "Euglycemic DKA (plasma glucose <200 mg/dL) has been described in pregnancy, alcohol ingestion, fasting or starvation, and in patients with T1DM and T2DM treated with SGLT2 inhibitors."

Key Pitfalls

1. Starvation/fasting - the most common cause of positive urine ketones in otherwise healthy people. No acidosis, no hyperglycemia.
2. Alcoholic ketoacidosis (AKA) - positive ketones with low or normal glucose. The mechanism is alcohol-induced suppression of gluconeogenesis + lipolysis.
3. SGLT2 inhibitor-related euglycemic DKA - glucose can be <200 mg/dL, so a "normal" glucose does NOT rule out DKA if the patient is on empagliflozin, dapagliflozin, etc.
4. Dipstick underestimates ketosis - it misses beta-OHB (the dominant ketone). A serum beta-hydroxybutyrate level is the more reliable test.

Bottom Line

Diagnostic Criteria for Alcoholic Ketoacidosis (AKA)

Classic Presentation (Required Clinical Context)

• History of chronic alcohol use (usually severe/advanced alcoholism)
• Recent binge drinking followed by sudden cessation of oral intake (1-3 days prior)
• Nausea, vomiting, and abdominal pain causing poor food intake
• Dehydration
• Alcohol level is typically low or undetectable by the time AKA develops (the binge has ended)

Rosen's Emergency Medicine: "Alcoholic ketoacidosis occurs most frequently in severe chronic alcoholics who have had a recent binge followed 1 to 3 days later by protracted vomiting, decreased food intake, dehydration, and abstinence."

Biochemical Criteria

Why the pH and Urine Ketones Can Be Misleading

1. Urine ketone dipstick may be NEGATIVE - The nitroprusside reaction on dipstick only detects acetoacetate. In AKA, the high NADH/NAD+ ratio from ethanol metabolism strongly shifts the equilibrium toward beta-OHB, so acetoacetate is very low. The dipstick underestimates (or completely misses) the true degree of ketosis. Serum beta-OHB is the correct test.
2. pH may not be acidic - Patients frequently have concurrent:
   • Metabolic alkalosis from vomiting (HCl loss)
   • Respiratory alkalosis from underlying liver disease These can mask the anion gap acidosis. The pH may be normal or even elevated, yet the patient still has significant ketonemia. The elevated anion gap may be the only clue.

NKF Primer on Kidney Diseases: "AKA almost always presents with an expanded AG, but acidemia is less universal... patients with AKA may not be acidic and rarely do they have a simple metabolic acidosis."

Comprehensive Clinical Nephrology: "The increase in NADH/NAD+ is reflected by a higher ratio of beta-hydroxybutyrate to acetoacetate. The nitroprusside reaction may be diminished by this redox shift despite the presence of severe ketoacidosis."

Pathophysiology in Brief

1. Massive catecholamine surge from alcohol withdrawal + volume depletion + starvation - far greater peripheral lipolysis than starvation alone, leading to marked free fatty acid delivery to the liver and severe ketoacid production.
2. Ethanol metabolism generates NADH - NADH accumulation inhibits hepatic gluconeogenesis (explaining why glucose stays low despite high counter-regulatory hormones) and shifts ketone equilibrium to beta-OHB.

Key Differentiating Features vs. DKA

Important Comorbidities to Exclude

• Lactic acidosis (from thiamine deficiency, sepsis, or shock)
• Toxic alcohol ingestion (methanol, ethylene glycol) - check osmolar gap
• Salicylate toxicity
• Pancreatitis, GI bleeding, pneumonia as precipitants

Symptom to Diagnosis (4th ed.): "Patients with alcoholic ketoacidosis often have concomitant lactic acidosis... toxic ingestions (methanol, ethylene glycol, or salicylate) should also be considered, especially in patients with a large osmolar gap."

Treatment (Confirms the Diagnosis)

• IV thiamine FIRST (before any glucose) - to prevent Wernicke encephalopathy
• IV dextrose + normal saline - glucose stimulates insulin, which shuts off ketogenesis
• Correct hypokalemia, hypomagnesemia, hypophosphatemia
• Resolution typically occurs within 12-24 hours

"Any patient with nausea and vomiting with a recent history of alcohol abuse should probably be treated for presumptive AKA until the diagnosis is clearly ruled out." - NKF Primer on Kidney Diseases