Jejunal biopsy is diagnostic in

biopsy reveals characteristic findings in the following diseases which may cause steatorrhea: sprue, amyloidosis, Whipple's disease, lymphoma, a-beta-lipoproteinemia, and scleroderma. In nontropical sprue (and to a lesser degree in tropical sprue), microscopic examination of the jejunum reveals blunting or absence of the villi, substitution of cuboidal for columnar surface cells, infiltration of the lamina propria with lymphocytes and plasma cells, and increased mitotic activity in the crypts of the unusually deep intestinal glands. In amyloidosis, which affects the intestinal tract in 50% of cases, there is deposition of amyloid in the lamina propria and around blood vessels. In Whipple's disease, villi of the intestinal mucosa are thickened and have bulbous tips, and the laminae propria contain foamy histiocytes and lipid deposits; also the macrophages contain a carbohydrate-protein complex which is readily demonstrated by the periodic-acid, Schiff staining technic. In lymphoma, mucosal lesions may be identical to those seen in sprue; on the other hand, diagnostic nodules of lymphocytes or unusual cellular infiltrations may be seen in the lamina propria. In a-beta-lipoproteinemia, numerous vacuoles of fat are found in the epithelial cells Ref Davidson edition23rd pg 809