The typical stool appearances described above are unmistakable. Greasy stools from a jaundiced patient point to biliary cirrhosis or pancreatic cancer. Microscopic examination showing fat globules and undigested meat fiber suggests pancreatic insufficiency. Microscopy permits identification of ova or parasites. Sudan III staining of a stool smear is a relatively simple and direct, but nonquantitative, screening test for fecal fat.
Abnormal findings are usual in primary jejunal disease but rare in other causes.
Although this test is popular in pediatric practice, complete urine collection in young children is difficult, and some investigators prefer measuring blood levels. Iron malabsorption can usually be inferred in a patient whose diet is adequate and who has no chronic blood loss or thalassemia but has an iron-deficiency state, indicated by low serum ferritin or iron levels. Diminished iron storage can be seen on bone marrow evaluation. Folic acid absorption is abnormal if a low serum or RBC folate level is found in a patient eating an adequate diet but not consuming excessive alcohol. Vitamin B 12 absorption is abnormal if serum B 12 is low.