IDO1 and cholesteryl ester measurement: P-values obtained from Tukey's HSD (Honestly Significant Difference) post-hoc analysis after one-way analysis of variance testing of percentage mucosal IDO-1 positive mRNA and IDO-1 H-score in the duodenal mucosa of dogs with PLE (n = 6), dogs with CE (n = 18) and healthy Beagle control dogs (n = 8).