Serum B12 concentration is elevated in patients receiving chronic parenteral nutrition, but is not a marker of intestinal failure-associated liver disease

Background: Cobalamin is released during hepatic cytolysis associated with liver injury. Serum B12 concentration is frequently elevated in patients that receive long-term parenteral nutrition (PN). We hypothesized that serum B12 concentration would become elevated in intestinal failure-associated liver disease and would reflect in disease severity. Methods: We retrospectively evaluated 13 patients with short bowel syndrome (<200 cm residual small intestine) that included complete terminal ileum resection (3 male and 10 female, aged 42 to 78 y) that had received parenteral nutrition (PN) 6.1±3 years. All 13 patients had received at least 1 liver biopsy for presumed intestinal failure-associated liver disease. At the time of biopsy, patients had received PN between 2 and 7 days a week (4.7±1.9 d). The liver biopsies were evaluated and prospectively scored for pathology using 3 independent scoring systems validated for nonalcoholic steatohepatitis and nonalcoholic fatty liver disease [Brunt, NAFLD activity score (NAS) and Dixon methods], whereby numeric values were assigned to degrees of steatosis, inflammation, and fibrosis. Serum B12 concentration and hepatic chemistries (aspartate transaminase, alanine transaminase, alkaline phosphatase, and bilirubin) were recorded within 1 week of the biopsies. Results: Thirteen biopsies were available for analysis. Serum B12 concentration and hepatic chemistries were available for all biopsy times. The mean serum B12 concentration was 619±222 pg/mL. The mean daily parenteral B12 dose was 3.3±1.3 mcg. Mean NAS, Brunt, and Dixon scores were 2, 1, and 1, respectively. The Spearman correlation coefficients between serum B12 concentration and liver biopsy scores were 0.15, 0.1, and 0.1 for the NAS, Brunt, and Dixon scores, respectively, indicating that there was no correlation between serum B12 concentration and liver pathology. The Spearman correlation coefficient between the NAS inflammation subscore and serum B12 concentration was 0.02. B12 concentration also failed to correlate with hepatic chemistries. There was surprisingly little correlation between serum B12 concentration and exogenous B12 daily dose through PN (r=0.19, P=0.45). Conclusions: Elevated serum B12 concentration is commonly encountered in patients who receive long-term parenteral nutrition. This does not seem to be an indicator of hepatic pathology; rather it may reflect the provision of excessive intravenous vitamin B12 and other as yet unknown factors.