Stool Examination

Sample for stool examination

1. The fresh stool can be examined immediately for moving organisms.
2. Stool in 10% formalin can be used for Helminths and protozoa.
3. A stool in formalin-ethyl acetate is used to concentrate the stool.
4. The smallest amount of stool needed for the examination is 2 to 5 grams.
5. For ova and parasites, there are three methods:
   1. Direct stool examination.
   2. Concentration method.
   3. The permanent stain of the stool.

Samples for various parasitic infestations:

Precautions for stool examinations:

1. Advise patients about the following things for at least 48 hours before the collection of the stool:
   1. Avoid mineral oils.
   2. Do not take bismuth.
   3. Don’t take antibiotics like tetracyclines.
   4. Anti-diarrheal drugs are non-absorbent.
   5. Avoid anti-malarial drugs.
   6. The patient should not have a barium swallow examination before the stool examination.
   7. Stop iron-containing drugs, meat, and fish 48 hours before the collection for occult blood.
2. Warm stools are better for the ova and parasites.
3. Don’t refrigerate the stool for ova and parasites.
4. Stools for ova and parasites can be collected in formalin and polyvinyl alcohol. These are used as a fixative.
5. If there is blood or mucus, that should be included in the stool because most of the pathogens are found in this substance.
6. Examine the stool before giving antibiotics or other drugs.
7. The semi-formed stool should be examined within 60 minutes of collection.
   1. The liquid stool should be examined within the first 30 minutes.
   2. The solid stool should be examined within the first hour of collection.
8. Trophozoites degenerate in liquid stool rapidly, so examine the stool within 30 minutes.
9. In the case of constipated cases, use non-residual purgative on the night before collecting the stool.

Indications for stool examination:

1. To evaluate the function and integrity of the GI tract.
2. To rule out the presence of WBCs and RBCs.
3. To find ova or parasites.
4. To see the presence of fat for malabsorption syndrome.
5. For screening for colon cancer.
6. For asymptomatic ulceration of the GI tract.
7. Evaluate diseases in the presence of diarrhea and constipation.
8. Summary of stool studies is done to evaluate:
   1. Intestinal bleeding.
   2. Infestation.
   3. Inflammatory diseases.
   4. Malabsorption.
   5. Different causes of diarrhea.

Stool preservatives are:

1. Preservatives for the wet preparation are:
   1. 10% formol-saline for the wet preparation. This is the best preservative as it kills bacteria and preserves protozoa and helminths.
   2. Sodium acetate formalin.
   3. Methionate iodine formalin. This is a good preservative for the field collection of the stool.
2. For staining, use Polyvinyl alcohol.
3. Avoid preservatives for the culture of stool.
   1. Usually, three parts of the preservatives and one part of the stool.

Gross Stool examination includes:

1. Color.
2. Consistency.
3. Quantity.
4. Odor.
5. Mucous.
6. Helminths.
7. Concretions (gallbladder stones rarely may be found).

Undigested food particles like:

1. Vegetable cells.
   1. Vegetable fibers.
   2. Plant hairs.
   3. Amorphous vegetable material.

2. Pollen grains are regular in size and often present in large numbers.

Stool examination: Stool showing pollen grains

Stool showing undigested citrus fruit (Oranges or grapefruit)

Muscle fibers:

1. These are usually light brown. Sometimes it may show striations.
2. Meat fibers and muscle fibers are seen in the stool. Their presence shows defective indigestion.
   1. The increased amount of meat fibers are found in:
      1. Malabsorption syndrome.
      2. A pancreatic functional defect like cystic fibrosis.

Stool examination: Stool muscle fibers

Starch granules:

1. It may be spherical if undigested; they have concentric layers of white, homogenous material.

Stool examination: Stool starch and iodine stain of starch result

Stool examination: Stool showing potato remnants

1. Fishbones.
2. Water.

Bacteria:

1.  On the stool smear, do the gram stain and see the bacteria. Normally there are bacteria in the stool.

Desquamated epithelial cells:

• This depends upon the size of the nuclei and the cytoplasm. These are usually from the anal canal mucosa.

Stool smear showing squamous epithelial cell and macrophagic cell

Polymorphonuclear leucocytes:

1. When stained, smears may show a nucleus divided into four separate spheres with peripheral chromatin.
   1. Also, show an apparent karyosome.
   2. The nuclear material is larger in proportion to the amount of cytoplasm compared to the amoebic cyst.
   3. The shapes of the nuclei are variable.

Macrophagic cells:

1. These have numerous inclusions in the dark-staining cytoplasm.
2. These need to differentiate from the intestinal amoebae. There are large particles in the cytoplasm.
3. The nucleus has no karyosomes.
4. Degenerated macrophagic cells lose their nucleus and have few ingested materials.
5. Also, the nucleus has a fine network of chromatin and large particle scattered.

Stool smear showing degenerated macrophagic cell

Digestive tract products:

1. Digestive tracts products like:
   1. Enzymes.
   2. Mucus.
   3. Bile pigments products.
2. Digested but not absorbed food.
3. Products produced by the decomposition of the stool are:
   1. Skatole.
   2. Indole.
   3. Various gases like H₂S, CO₂, and nitrogen.

Macroscopic or gross appearance of the stool:

1. The gross findings of the stool are important. Note the consistency and the color of the stool.
2. Try your best to examine the stool as received in the lab. In case of delay, use the preservatives.
3. The mushy or liquid stool may suggest the presence of protozoan trophozoites. If the stool is examined, within one-half hours gives the best result.
4. Helminth eggs and larvae are found in the liquid or formed stool. Grossly you may see proglottids or adult tapeworms.

Physical character and appearance:

The consistency of the Stool (gross appearance):

1. The stool consistency may be:
   1. Normal is soft and formed.
   2. Loosely formed stools.
   3. Watery stools.
   4. Thin stools.
   5. Pellet-like stools.
   6. Dry or hard stools are found in constipated patients.
   7. Puttylike stools.
   8. The small round hard stool is due to habitual constipation.
2. Pasty stools are due to high-fat contents and are seen in:
   1. Common bile duct obstruction.
   2. In Celiac disease, the stool looks like aluminum paint.
   3. Cystic fibrosis due to pancreatic involvement and are greasy.
3. Diarrheal stools are watery.
4. Steatorrhea stool is:
   1. 1. Large in amount.
      2. Frothy.
      3. Foul-smelling.
5. Constipated stools are firm and may see spherical masses.
6. Ribbon-like stool suggests the spastic bowel, rectal narrowing, stricture, or partial obstruction.
7. The hard stool is due to excessive water absorption and prolonged contact with the colonic mucosa.

Color of the stool:

1. The normal color is due to the presence of stercobilinogen and is brown.
2. Yellow or yellow-green color is seen in diarrhea.
3. Black and tarry (related to consistency) stools are due to bleeding of the upper GI tract from tumors.
4. The maroon or pink color is from the lower GI tract due to tumors, hemorrhoids, fissures, or inflammatory processes.
5. Clay-colored stools are due to biliary tract obstruction.
6. Mucous in the stool indicate constipation, colitis, or malignancy.
7. The pale color with a greasy appearance is due to pancreatic deficiency leading to malabsorption.

Causes of different colors of the stool:

Quantity of the stool:

1. Normally there is 100 to 200 G/day.
   1. With a vegetable diet, maybe 250 g/day.
2. Many disorders cause large, bulky stools, even in people who don’t eat much.
   1. Like malabsorption syndrome and carbohydrate indigestion.
3. Your stool size has more to do with how well you digest your foods than what you eat.
4. Some foods produce larger stools because they don’t break down completely.
5. Some gastrointestinal disorders also cause poor food breakdown and absorption, which leads to large, bulky stools.

The odor of the stool:

1. The foul odor is caused by undigested protein and by excessive intake of carbohydrates.
   1. Stool odor is caused by indole and skatole, formed by bacterial fermentation and putrefaction.
2. A bad odor is sickly produced by undigested lactose and fatty acids.
3. The odor is increased due to excess intake of proteins.
4. The putrid odor is due to severe diarrhea of malignancy or gangrenous dysentery.

Mucus in the stool:

1. The mucosa of the colon produces mucus in response to parasympathetic stimulation.
2. Pure mucous is translucent, gelatinous material clinging to the stool’s surface. This may be seen in the following:
   1. Severe constipation.
   2. Mucous colitis.
   3. Excessive straining of the stool.
   4. Emotionally unstable patient.
3. Mucus in diarrhea with microscopically present RBCs and WBCs are seen in:
   1. Bacillary dysentery.
   2. Ulcerative colitis.
   3. Intestinal tuberculosis.
   4. Amoebiasis.
   5. Enteritis.
   6. Acute diverticulitis.
   7. Ulcerating malignancy of the colon.
4. Mucus with blood that is clinging to stool is seen in:
   1. Malignancies of the colon.
   2. Inflammatory lesion of the rectal canal.
5. An excessive amount of mucus was seen in:
   1. Villous adenoma of the colon.
   2. This depends upon the dietary intake.

Stool physical character and possible causes:

The chemical examination includes:

1. Stool pH.
2. Reducing substances.
3. For occult blood.
4. Presence of fat, carbohydrate, and proteins.

pH of the stool:

1. Normally stool is slightly acidic or alkaline, or neutral.
   1. pH is 7.0 to 7.5, depending on the diet.
   2. Newborn pH = 5.0 to 7.5.
2. The pH of the stool depends upon the diet and bacterial fermentation in the small intestine.
3. Carbohydrate changes the pH to acidic, while protein breakdown changes to alkaline.
   1. The breastfed infant’s pH has a slightly acidic stool.
   2. Bottle-fed infants have a slightly alkaline stool.
4. The pH stool test helps to evaluate carbohydrate and fat malabsorption.
5. pH stool also helps to know disaccharidase deficiency.
6. Alkaline (Increased pH) stool is seen in:
   1. Colitis.
   2. Villous adenoma.
   3. Diarrhea.
   4. Antibiotic therapy.
   5. Excess intake of proteins.
7. Acidic (Decreased pH) stool seen in:
   1. Fat malabsorption.
   2. Disaccharidase deficiency.
   3. Carbohydrate malabsorption.
   4. Excess intake of carbohydrates.
8. Precautions for pH estimation:
   1. Barium intake and laxatives change the pH.
   2. If the specimen is contaminated with urine, we must discard the sample.

Presence of Fat in the stool:

1.  The fat in the stool shows the possibility of:
   1. Malabsorption.
   2. Deficiency of pancreatic digestive enzyme.
   3. Deficiency of Bile.

Urobilinogen in the stool:

1. This is normally found in 40 to 280 mg/24 hours (100 to 400 Ehrlich units/100 gm).

Coproporphyrin in the stool:

1. 400 to 1000 mg/24 hours.

Fat in the stool:

1. Normally absent, which is less than 7 grams / 24 hours during three days period.
2. This is less than 30% of dry weight (On a diet of 50 grams of fat per day).
3. Normal
   1. 2 to 6 grams/24 hours (7 to 21 mmol/day).

Calcium in the stool:

1. This is about 0.6 grams / per 24 hours.

Stercobilinogen in the stool:

1. It is normally 40 to 280 mg/day, averaging 150 mg/day.

Nitrogen in the stool:

1. It depends upon the nature of the diet.
2. The normal amount is 1 to 1.5 g/day (<2.5 grams/day).

Microscopic stool Examination:

1. Presence of leukocytes (pus cells).
2. Presence of Red Blood Cells.
3. Ova and parasites.
4. Presence of meat fibers and muscle fibers.
5. Presence of fat.
6. Yeast and molds.
7. Bacteria.

Presence of Leukocytes:

1. Normally, there are no WBCs.
2. WBCs only appear in infection or inflammation.
3. Their presence is important in case of diarrhea or dysentery.
4. >3 WBCs /high fields are seen in ulcerative colitis and bacterial infection.
5. Greater numbers of WBCs indicate invasive pathogens.

Stool examination: Stool with the presence of WBCs and RBCs

6. Viruses and parasites don’t cause the presence of  WBCs in the stool.
7. Increased number of WBCs seen in the stool:
   1. Bacillary dysentery.
   2. Chronic ulcerative colitis.
   3. Shigellosis.
   4. Salmonella infection.
   5. Yersinia infection.
   6. Invasive E.coli diarrhea.
   7. Fistula of anus or rectum.
   8. Localized abscess.
8. Few WBCs are seen in amoebiasis.
   1. Also, WBCs are seen in typhoid.

The absence of WBCs seen in some of the diarrhoeal conditions alike:

1. Cholera.
2. Viral diarrhea.
3. Drug-induced diarrhea.
4. Amoebic colitis.
5. Non-invasive E.coli diarrhea.
6. Parasitic infestation.
7. Toxigenic bacterial infection.

Presence of Red Blood Cells in the stool:

1. Normally RBCs are absent.
2. Epithelial cells are present, and these are increased with GI tract irritation.
3. Few WBCs are seen, which may be increased due to GI tract inflammation.
4. Blood in the stool can be:
   1. Bright red from the bleeding in the lower GI tract.
   2. Maroon in color.
   3. Black and tarry from bleeding from the upper GI tract.
   4. Occult blood (not visible to the naked eye).
5. Causes of blood in stool:
   1. Hemorrhoids.
   2. Cancer.
   3. Dysentery.
6. Make a smear from the mucus or blood-colored area from the watery or semiformed stool.

Stool examination: Stool gross appearance of mucus with blood

Presence of crystals and other substances:

1. Crystals of calcium oxalate, fatty acids, and triple phosphate are commonly present.

Stool examination: Stool showing crystals

2. Charcot-Leyden crystals are seen in parasitic infestation, especially in amoebiasis.

Stool Charcot-Leyden crystals

3. Undigested vegetable fibers and meat fibers are seen sometimes.
4. Neutral fat globules stained with Sudan may be seen normally at 0 to 2 +.
5. Hematoidin crystals are sometimes seen after GI tract hemorrhage.

Stool examination: Stool with the presence of WBCs and RBCs

Ova and parasites:

1.  Normally there are no parasites or eggs in the stool sample.
2. Multiple stool samples are needed to rule out the parasitic infestation for at least three consecutive days.
3. An abnormal result means parasites or eggs are present in the stool. Such infections include:
4. Roundworms: Ascaris lumbricoides.
5. Hookworms: Necator americanus.
6. Pinworms: Enterobius vermicularis.
7. Whipworm: Trichuris trichiura.
8. Tapeworms: Diphyllobothrium latum, Taenia saginata, and Taenia solium.
9. Protozoa: Entamoeba histolytica (an amoeba) and Giardia lamblia (a flagellate)
10. Strongyloidiasis.

Summary of the normal stool examination:

The summary of normal findings in the stool examination:

1. Quantity
   1. The bulk of the stool is 100 to 200 grams.
   2. It may be up to 250 grams on a vegetable diet.
2. Amount of water
   1. Normally there is up to 75 % of water in the stool.
   2. It is interesting that our body also has roughly 75% of water.
3. Gross appearance
   1. Normal is soft and formed.
   2. Scanty mucous was seen.
   3. Abundant mucous was seen.
   4. Mucous with blood seen.
   5. Grossly fibrous.
   6. Homogenous appearance.
4. Color
   1. The normal color is yellowish-brown due to the presence of bilirubin and bile.
   2. In infants, the color is green, and the stool is loose or pasty.
   3. Various colors depending on diet.
      1. Clay color stool is seen in biliary obstruction.
      2. Tarry stool is seen if more than 100 ml of blood comes from the upper GI tract.
      3. The red color is due to blood in the large intestine, undigested beets, or tomatoes.
      4. The black stool is seen due to blood, iron, or bismuth medication.
5. Consistency may be:
   1. Soft.
   2. Formed.
   3. Semiformed.
   4. Hard.
   5. Loose.
   6. Diarrheal.
   7. Watery like a fluid.
6. pH
   1. This is from 7.0 to 7.5.
   2. This may be acidic with high lactose intake.

Stool normal findings

In routine stool examination consists of the following: