The presence of D-Lactate (D-lactic acid) in the blood is a reflection of bacterial overgrowth in the gastro-intestinal tract. Raised D-lactate is a rare finding in humans, but a common problem among ruminants (veterinary surgeons recognise that D-lactate production in cows is potentially fatal). D-lactic acidosis in the human as first described in association with short bowel syndrome (post-operative bacterial overgrowth) .
D-lactate should not be confused with L-lactate, which is a normal product of anaerobic metabolism. Unlike the L-form, D-lactate is not metabolised by mammals and its elimination from the body depends mainly on renal excretion.
D-lactate is produced from non-absorbed carbohydrates by colonic bacteria (which may also proliferate in the ileum). The absorption of large amounts of D-lactate can cause metabolic acidosis, altered mental status and a variety of other neurologic symptoms, in particular dysarthria and ataxia [2,3,4]. Its measurement is part of the differential diagnosis of chronic fatigue syndrome . Although a temporal relationship has been described between elevations of plasma D-lactate and the accompanying encephalopathy, the exact neurological mechanisms remain undescribed .
Otherwise healthy children with gastroenteritis may also develop D-lactic acidosis.
There are a number of other tests of gastro-intestinal function available from Biolab – the gut fermentation test, the PEG profile (gut permeability), the measurement of plasma short-chain polypeptides and the lactulose breath hydrogen test. Each of these tests provides somewhat different information from the D-lactate test, which is specific for the presence of D-lactate-producing bacteria in the gut (probably Enterococcus and Streptococcus spp. ).
Unaffected subjects have plasma concentrations of D-lactate of less than 60umol/L.
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