Stool analysis determines the various properties of the stool for diagnostic purposes. Some of the more frequently ordered tests on feces include tests for leukocytes, blood, fat, ova, parasites, and pathogens (Table 4.1). (See Chapter 7 for stool culture.) Stool is also examined by chromatographic analysis for the presence of gallstones. The recovery of a gallstone (precipitated by cholesterol or bile pigments) from feces provides the only proof that a common bile duct stone has been dislodged and excreted. Stool analysis also screens for colon cancer and ulcerations without symptoms or other masses of the GI tract and evaluates GI diseases in the presence of diarrhea or constipation. Stool analysis is done in immunocompromised persons for parasitic diseases. Fat analysis is used as the gold standard to diagnose malabsorption syndrome. The Centers for Disease Control and Prevention recommends that stool samples submitted for enteric pathogen testing should also be tested for Shiga toxin (produced by Escherichia coli O157:H7 and other 
strains of E. coli).

Patients and healthcare personnel may dislike collecting and examining stool samples; however, this natural aversion must be overcome in light of the value of a stool examination for diagnosing disturbances and diseases of the GI tract, the liver, and the pancreas.