Simultaneous measurement of peritoneal and plasma lactic acid can be used to assess patients with acute abdominal disease. In patients with gangrenous viscera, perforated hollow viscera, peritonitis, or intra-abdominal abscess, the peritoneal lactic acid levels are greater than plasma levels, whereas other patients with abdominal pain tend to have similar values in both peritoneal fluid and plasma.
Specimen Collection: Peritoneal fluid and plasma must be collected within a few minutes of each other to provide a valid interpretation.
difference between peritoneal and plasma lactic acid =
= (peritoneal lactic acid in mmol/L) - (plasma lactic acid in mmol/L)
ratio of peritoneal-to-plasma lactic acid =
= (peritoneal lactic acid in mmol/L) / (plasma lactic acid in mmol/L)
where:
• conversion from CU to SI units: conventional units mg/dL; factor 0.111
Interpretation:
• A difference of 1.5 mmol/L or more had a sensitivity and specificity of 100% in identifying patients with gangrenous viscera, perforated hollow viscera, peritonitis, intra-abdominal abscess.
• A difference of 2.0 mmol/L showed sensitivity of 84%, specificity of 100%, positive predictive value of 100% and negative predictive value of 84%.
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