<prompt> Which is best for diagnosis of small intestinal mucosal disease?Small bowel Series using barium contrastUrinary D- xylose testSmall intestinal mucosal biopsyBreath hydrogen test  <response>: Mucosal disease of small intestine : Infection esp. Giardia, Whipples disease, tropical sprue, inflammatory diseases esp. Crohns disease, radiation enteritis, eosinophilic enteritis, ulcerative jejunitis, mastocytosis, tropical sprue, infiltrative disorders amyloidosis, scleroderma, lymphoma, collagenous sprue, microscopic colitis, biochemical abnormalities gluten-sensitive enteropathy, disaccharidase deficiency, hypogammaglobulinemia, abetalipoproteinemia, amino acid transpo deficiencies, endocrine disorders diabetes mellitus, hypoparathyroidism, adrenal insufficiency, hypehyroidism, Zollinger-Ellison syndrome, carcinoid syndrome For some small intestinal disorders that are characterized by diarrhea or malabsorption, the biopsy findings may be distinctive and lead to a specific diagnosis. Whipple Disease- -PAS positive inclusions that is Schiff reagent positive inclusion inside the macrophages of lamina propria - Caused by bacteria - Tropheryma whipplei Note Gluten sensitive enteropathy is strongly associated with HLA DQ2 and HLA DQ8 