Plasma Citrulline Concentration

OBJECTIVES Postabsorptive plasma citrulline concentration has been proposed as a reliable marker of small bowel absorptive capacity in short bowel patients. The aim of this study was to address the potentially confounding impact of intestinal inflammation. METHODS Fifty-five patients were selected according to diagnosis, small bowel length, and degree of bowel inflammation. (a) Crohn's disease (CD) with massive small bowel resection leaving ≤50 cm (N = 6), (b) CD with 50–150 cm remaining (N = 9), (c) CD with no resection but active inflammation (high C-reactive protein [CRP] and Crohn's Disease Activity Index [CDAI] >220) (N = 7), (d) CD without resection or active inflammation (normal CRP and CDAI <150) (N = 9), (e) mesenteric infarction (MI) with resection leaving ≤50 cm (N = 6), (f) MI leaving 50–150 cm (N = 6), (g) active celiac disease (N = 6), (h) healthy volunteers (N = 6). Postabsorptive fasting plasma citrulline was measured using reverse-phase, high performance liquid chromatography. Absorptive capacity and permeability were also measured after oral sugar-mix ingestion (5 g lactulose, 1 g L-rhamnose, 0.5 g D-xylose). RESULTS The plasma citrulline strongly correlated with small bowel length (P < 0.0001) and xylose absorption (P < 0.001). No correlation was found with CDAI, permeability, CRP, albumin, sedimentation rate, white cell count, or platelet count. Citrulline was significantly higher (P < 0.0004) in CD and MI patients with a remnant small bowel length of 50–150 cm (mean 21.0 μmol/L) than in those with length ≤50 cm (mean 9.2 μmol/L). CONCLUSIONS Plasma citrulline concentration is a simple and reliable surrogate for small bowel absorptive capacity and is not influenced by intestinal inflammation.