How useful is D-lactate (d-lactic acid) as a marker for lactic acidosis of gastrointestinal (GI) origin?

D-Lactate as a Marker for Lactic Acidosis of GI Origin

D-lactate is not a sufficiently accurate biomarker for lactic acidosis of gastrointestinal origin and should not be relied upon as a primary diagnostic tool. 1, 2

Diagnostic Value of D-Lactate

D-lactate has limited utility as a marker for lactic acidosis of gastrointestinal origin for several reasons:

• According to the World Society of Emergency Surgery guidelines, no accurate biomarkers have been identified to conclusively diagnose intestinal ischemia or lactic acidosis of GI origin 1
• A cross-sectional diagnostic study of 129 patients found that D-lactate was neither sensitive nor specific enough for the differential diagnosis of acute mesenteric ischemia (AMI) 1
• D-lactate is primarily useful in a specific subset of lactic acidosis cases:
  • D-lactic acidosis in patients with short bowel syndrome
  • Patients with intestinal bacterial overgrowth
  • Those who have undergone bariatric surgery 2, 3

When D-Lactate Is Clinically Relevant

D-lactate becomes clinically significant in specific scenarios:

• Short bowel syndrome: D-lactate levels >3 mmol/L confirm D-lactic acidosis in these patients 3
• Bacterial overgrowth: Excessive fermentation of malabsorbed carbohydrates by colonic bacteria produces D-lactic acid 3, 4
• Post-bariatric surgery: Altered GI anatomy can lead to D-lactic acidosis 3

In these specific conditions, D-lactate can help diagnose D-lactic acidosis, which presents with:

• Neurological symptoms (confusion, ataxia, slurred speech)
• Metabolic acidosis with high anion gap
• Normal L-lactate levels (routine lactate tests only measure L-lactate) 3, 5

Better Markers for GI-Origin Lactic Acidosis

For diagnosing lactic acidosis of GI origin, particularly in acute mesenteric ischemia:

• L-lactate: More reliable than D-lactate, with elevated levels (>2 mmol/L) associated with irreversible intestinal ischemia (HR: 4.1,95% CI: 1.4-11.5) 1
• D-dimer: More useful than D-lactate, with D-dimer >0.9 mg/L showing specificity, sensitivity, and accuracy of 82%, 60%, and 79%, respectively 1
• Clinical presentation: Lactic acidosis combined with abdominal pain should prompt consideration for early CT angiography, even when the patient may not otherwise appear clinically ill 1

Clinical Algorithm for Suspected GI-Origin Lactic Acidosis

1. Measure serum L-lactate (not D-lactate) and D-dimer
2. If L-lactate >2 mmol/L with abdominal pain, consider urgent CT angiography
3. Consider D-lactate testing only when:
   • Patient has short bowel syndrome or history of bariatric surgery
   • Unexplained neurological symptoms with metabolic acidosis
   • Normal L-lactate with high anion gap acidosis

Pitfalls and Caveats

• Routine clinical lactate measurements only detect L-lactate, not D-lactate 3
• Special assays are required to measure D-lactate 3
• D-lactate levels can fluctuate significantly within hours (0.5-3.1 mmol/L in plasma) 4
• D-lactate is metabolized and excreted by humans, contrary to earlier beliefs 4
• Patients may present with lactic acidosis due to dehydration and decreased oral intake, which can be misattributed to intestinal ischemia 1
• Relying solely on D-lactate for diagnosis of GI-origin lactic acidosis may lead to missed diagnoses and delayed treatment of critical conditions like acute mesenteric ischemia 1