Stool Examination

Gross and Microscopic Inspection

An acholic stool suggests biliary obstruction; a tarry stool indicates gastrointestinal (GI) bleeding; and a red stool signifies bleeding from the lower GI tract. The shape of the stool is usually reliably reported by the patient, and the appropriate deductions may be made without the physician observing the stool. Diarrheal stool is loose and watery, but stool associated with malabsorption can be large and greasy, often staining the toilet bowl. The Bristol Stool Scale clearly describes the foam, form, and character of the bowel movement material and has been useful in clinical and research settings ( Fig. 81.2 ). The character of stools is also discussed thoroughly in Chapters 64 (diarrhea) and 85 (constipation).

Microscopic examination of stool can be helpful when inflammatory cells (polymorphonuclear or eosinophilic) are identified. Furthermore, ova and parasites can be identified as eggs or larvae under the microscope.