D-Lactic acidosis

OVERVIEW

• aka D-lactic encephalopathy
• rare cause of high anion gap metabolic acidosis (HAGMA)
• typically occurs in patients short bowel syndrome or following jejuno-ileal bypass surgery
• usual L-lactate assay is normal, so a high index of suspicion is needed in at-risk patients

CAUSE

Risk factors

• abnormal gut structure (blind loops, short gut syndrome, jejuno-ileal bypass surgery)
• ischaemia
• small intestinal bacterial overgrowth (SIBO)
• antibiotics that select out Lactobacillus and Streptococcus bovis subtypes
• high carbohydrate load
• the possible causative role of probiotics is controversial (Rao et al, 2018)

Mechanism

• malabsorbed carbohydrate is fermented by an abnormal bacterial flora in the colon
• this produces excessive amounts of D-lactate
• acidic pH generated as a result of D-lactate production further propagates production of D-lactic acid, giving rise to a vicious cycle
• high amounts of D-lactate are absorbed into the circulation, resulting in an elevated concentration of D-lactate in the blood
• unclear if D-lactate itself, or other (co-absorbed) factors, is responsible for neurological symptoms

CLINICAL FEATURES

• Neurological symptoms
  • altered mental status, slurred speech, and ataxia (may appear “drunk”)
  • “brain fogginess”
• Presence of risk factors
• absence of another attributable cause

INVESTIGATIONS

• high anion gap (HAGMA)
• L-lactate normal (standard lactate assay)
• elevated plasma D-lactate level (> 3 mmol/L is diagnostic)
• normal glucose

MANAGEMENT

• supportive, including:
  • management of confusional state and falls risk
  • correction of acidosis (e.g. renal replacement therapy in severe cases)
• withdraw contributing factors
• restrict enteral carbohydrate intake
• antibiotics to clear causative colonic flora (rarely)
• for refractory cases, consider surgery (e.g. small intestine transplant, lengthening procedures)

References and Links

Journal articles

• Kowlgi NG, Chhabra L. D-lactic acidosis: an underrecognized complication of short bowel syndrome. Gastroenterol Res Pract. 2015;2015:476215. [pubmed] [article]
• Petersen C. D-lactic acidosis. Nutr Clin Pract. 2005;20(6):634-45. [pubmed]
• Rao SSC, Rehman A, Yu S, Andino NM. Brain fogginess, gas and bloating: a link between SIBO, probiotics and metabolic acidosis. Clin Transl Gastroenterol. 2018;9(6):162. [pubmed] [article]