Stool

Question 1

What are stool studies in general used for?

Answer 1

Used to evaluate function and integrity of the bowel
Performed to evaluate patients with intestinal bleeding, infections, infestations, inflammation, malabsorption, and diarrhea
Most results are available within 24 hours but some may take days to weeks

Question 2

What is the stool for occult blood (hemoccult) test used for?

What is normal?

Answer 2

Used for colorectal cancer screening of asymptomatic patients.

Normal is no occult blood.

Normally only minimal quantities (2-2.5 mL) of blood are passed into the GI tract and is usually not enough to cause a positive test result.

This test can detect occult blood when 5 mL of blood is lost per day

Question 3

What color on the stool card for the hemoccult test indicates a positive result?

Answer 3

Blue color means the stool contains blood.

No blue = no blood

Question 4

What are the interfering factors for the stool for occult blood (hemoccult) test?

Answer 4

Bleeding gums following a dental procedure or disease

Animal hemoglobin of ingested animal meat may cause a false positive result, although 8 oz. of cooked red meat per day will usually still have guaiac negative results

Question 5

What are the test results for the stool for occult blood (hemoccult) test?

Answer 5

GI tumor (cancers and polyps) – mucosa over neoplasm is friable

Peptic diseases (esophagitis, gastritis, and ulceration)

Varices (Esophageal) – large venous complexes covered by thin lining of mucosa. With increased intraabdominal pressure, they can rupture and bleed

Inflammatory bowel disease (ulcerative colitis, Crohn disease) – thickened and friable mucosa
Ischemic bowel disease – mucosa is the first layer affected by diminished blood supply. It sloughs and minor bleeding occurs

GI trauma – penetrating or blunt can cause bleeding

Recent GI surgery

Hemorrhoids and other anorectal problems

Question 6

What is the most common non-neoplastic cause of blood in stool?

Answer 6

Hemorrhoids and other anorectal problems – anorectal pathology is most common non-neoplastic cause of blood in stool

Question 7

What is * Melena?*

Answer 7

black tarry feces associated with GI bleed, caused by the oxidation of iron in hemoglobin during passage through the ileum and colon. Usually associated with upper GI bleed

Question 8

What is Hematochezia?

Answer 8

passage of bright red blood from the rectum. Usually associated with lower GI bleed

Question 9

What is the Apt Test used for?

What is normal?

Answer 9

Screening test to determine if blood in stool or amniotic fluid of newborn is fetal blood or swallowed maternal blood.

Normal is no newborn blood present and maternal blood is present.

Newborns may have a serious disease causing blood in the stool or may simply be defecating maternal blood that was swallowed during birth or breastfeeding

Question 10

When sodium hydroxide is added to the stool, what happens to the maternal blood and what happens to the fetal blood?

(Apt Test)

Answer 10

Maternal blood will dissolve leaving a brown stain.

Newborn blood will not dissolve and red blood will remain in the specimen

Question 11

What are the test results for the Apt Test?

Answer 11

Maternal blood – newborn usually defecates maternal blood in first 3-5 days. If maternal nipple disease exists, then the blood in the stool may persist in a breastfed newborn.

Fetal blood – indicates disease in GI tract of the newborn

Question 12

What is the Clostridial Toxin Assay used for?

What is normal?

Answer 12

Indicated in patients with diarrhea who have been taking broad spectrum antibiotics or in immunosuppressed patients with diarrhea even without taking antibiotics. The normal bowel flora is depressed allowing C. difficile to overgrow.

Normal is negative

Question 13

What is detected in the Clostridial Toxin Assay?

Answer 13

Bacteria releases a toxin that causes necrosis of colon epithelium, so toxin detection is diagnostic of clostridial enterocolitis (pseudomembranous colitis).

Diagnosed by identifying toxin by immunoassay (new method only takes 60-90 minutes) or stool culture for C. difficile

Question 14

What is Fecal Fat used for?

What is normal?

Answer 14

Used to confirm the diagnosis of steatorrhea which is suspected with large, greasy, foul smelling stools. High fecal fat content confirms the diagnosis

Normal findings: Fat 2-6 g/24 hrs.; retention coefficient >= 95%

Retention coefficient used for children to measure difference between ingested fat and fecal fat and expressing the difference (fat retained) as a percentage of ingested fat

Question 15

What causes increased levels of Fecal fat?

Answer 15

Cystic fibrosis – poor pancreatic function

Malabsorption from sprue, celiac disease, Whipple disease, Crohn disease (regional enteritis) – absorptive capability of stool is reduced with decreased transit time leading to fat not being absorbed

Maldigestion due to obstruction of pancreatobiliary tree (cancer, stricture, gallstones)

Short gut syndrome due to surgical resection or bypass or congenital abnormality – decreased transit time

Question 16

What is the stool culture used for?

What is normal?

Answer 16

Includes stool for culture and sensitivity, stool for ova and parasites.
Indicated with persistent diarrhea, fever, and bloating.

Be suspicious with well water exposure, prolonged course of antibiotics, or travel outside the US.

Normal findings are normal intestinal flora

Question 17

What are some pathogens that might affect the stool?

Answer 17

Several bacteria are pathogens, including Salmonella, Shigella, Campylobacter, Yersinia, pathogenic E. coli, Clostridium, and Staphylococcus

Parasites may also affect the stool – Ascaris (hookworm), Strongyloides ( tapeworm), Giardia (protozoans), and Cryptosporidium (especially in AIDS patients)

Normal flora can become pathogenic if overgrowth occurs due to antibiotics, immunosuppression, or overaggressive catharsis

Question 18

What are stool culture interfering factors?

Answer 18

Urine may inhibit bacterial growth so should not be mixed with stool.

Drugs may affect test results including antibiotics, bismuth, and mineral oil

Question 19

What are the possible test results for stool culture?

Answer 19

Bacterial, protozoan, or parasitic enterocolitis – organisms grown on special culture plates

Parasites – detected on a smear of stool

Question 20

What is the Tape test used for?

Answer 20

Used when pinworms (Enterobius) are suspected.
Place a strip of clear tape in perianal region.
Apply before bedtime (female worm lays eggs at night at the perianal area) and remove in morning before arising from bed

Press sticky surface of tape to a glass slide and examine under the microscope for pinworm ova

Question 21

What are fecal leukocytes used for?

When can you give antidiarrheal medication?

What is normal?

Answer 21

Used to determine the type of diarrhea, invasive or noninvasive, to the mucosa of the colon.

If none is present, an antidiarrheal medication can be given.
If fecal leukocytes are present, no antidiarrheal medication should be given.

Normal – no leukocytes present

Question 22

What does the presence of fecal leukocytes indicate?

Answer 22

Presence of fecal leukocytes indicates the cause of the diarrhea is an organism such as toxin producing E. coli or a process that is breaking the mucosal barrier of the colon.

Question 23

What does the Absence of fecal leukocytes indicate?

Answer 23

Usually not present when mucosa is not invaded, such as viral enteritis.

Absence of blood and leukocytes usually means the diarrhea is self-limiting and can be treated symptomatically.

C. difficile may or may not have leukocytes, so can’t rely on presence of leukocytes to make the diagnosis

Question 24

What is the Rotavirus antigen used for?

What is normal?

What is Rotavirus? How is it transmitted?

Answer 24

Used to detect rotavirus antigen in stool of pediatric patients.

Normal is negative. Presence of rotavirus in neonates less than 2 weeks old is inconclusive.

Rotavirus is a diarrheal disease. The virus replicates in epithelial cells of the small intestine and is pathogenic in infants and children during winter months.

It is transmitted by fecal-oral route