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Fecal smear is a laboratory test to check a stool sample for microscopic organisms that can cause diseases in the digestive tract.

A stool sample is needed.

There are many ways to collect the sample. You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. One test kit supplies a special toilet tissue that you use to collect the sample. When finished, put the sample in a clean container provided by your doctor's office.

To collect the sample from a child in diapers, line the diaper with plastic wrap. If the plastic wrap is positioned properly, you can isolate the stool from the child's urine. Preventing the mixing of urine and stool will give a better sample. When finished, put the sample in a clean container provided by your doctor's office.

Make sure you follow your doctor's instructions for returning the sample. Return the sample to the laboratory as soon as possible. The sample should not include toilet tissue or urine.

The stool sample is sent to a lab where a small amount is placed on a slide. The slide is placed under a microscope and checked for the presence of abnormal organisms such as bacteria, fungi, or viruses. A stain may be applied that highlights certain organisms under the microscope.

There is no preparation needed.

There is no discomfort.

Your doctor may order this test if you have severe, persistent (won't go away), or recurrent (keeps coming back) diarrhea of an unknown cause. The test result may be used to select the proper antibiotic treatment.

A normal result means no disease-causing organisms are present.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

An abnormal result means that abnormal bacteria or other organisms have been found in the stool sample, which may signal an infection of the digestive tract.

There are no risks associated with a fecal smear.

Stool smear

DuPont HL. Approach to the patient with suspected enteric infeciton. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 305.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.