Citrulline is the amino acid N-(aminocarbonyl)-L-ornthine which was first isolated from the watermelon (Citrullus vulgaris). The molecular weight is 175.19 Daltons and 1 mg/dL = 0.5708 µmol/L.
Patients were evaluated at least 2 years after the last "digestive circuit modification" which allows for intestinal adaptation.
Patients were given oral feedings without enteral support. Parenteral nutrition was stopped at least 8 hours before blood collection and after an overnight fast.
estimated small bowel length in cm =
= 4.348 * ((plasma citrulline concentration in µmol/L) - 5.68) =
= (4.348 * (plasma citrulline concentration)) - 24.7
For a patient who is hyperphagic (intake 2.4 +/- 0.6 times resting energy expenditure and 2.2 g protein +/- 0.6 per kg):
estimated small bowel length in cm in a hyperphagic patient =
= 6.25 * ((plasma citrulline concentration in µmol/L) - 4.47) =
= (6.25 * (plasma citrulline)) - 27.9
For a patient who is normophagic (intake approximately half that of the hyperphagic patient):
estimated small bowel length in cm in a normophagic patient =
= 6.67 * ((plasma citrulline concentration in µmol/L) - 11.7) =
= (6.67 * (plasma citrulline)) - 78
A plasma citrulline concentration > 20 µmol/L identifies patients with no or transient intestinal failure, while a plasma citrulline concentration <= 20 µmol/L is associated with permanent intestinal failure (sensitivity 92% and specificity 90%).
