A stool analysis is a series of tests done on a stool (feces) sample to help diagnose certain conditions affecting the digestive tract. These conditions can include infection (such as from parasites, viruses, or bacteria), poor nutrient absorption, or cancer.
For a stool analysis, a stool sample is collected in a clean container and then sent to the laboratory. Laboratory analysis includes microscopic examination, chemical tests, and microbiologic tests. The stool will be checked for color, consistency, amount, shape, odor, and the presence of mucus. The stool may be examined for hidden (occult) blood, fat, meat fibers, bile, white blood cells, and sugars called reducing substances. The pH of the stool also may be measured. A stool culture is done to find out if bacteria may be causing an infection.
Stool Examination – Part 1 – Stool Analysis , Stool for ova and parasite, Complete Stool studies
- A random stool sample can be taken.
- More than 2 grams of the stool is needed
- To rule out worm infestation three consecutive stools are tested.
- Collect three stools in the span of 10 days.
- Two samples on alternate days.
- One sample after purgation.
- Collect the sample in clean, dry urine free container.
- In the case of Infants, collect from the diaper.
- Advise patients for the following things for at least 48 hours before the collection of the stool:
- Avoid mineral oils.
- Do not take bismuth.
- Antibiotics like tetracyclines.
- Anti-diarrheal drugs which are non-absorbent.
- Avoid anti-malarial drugs.
- The patient should not have a barium swallow examination before the stool examination.
- For occult blood stop iron-containing drugs, meat and fish at least 48 hours before the collection.
- Warm stools are better for the ova and parasites.
- Don’t refrigerate the stool for ova and parasites.
- Stool for ova and parasites can be collected in formalin and polyvinyl alcohol. These are used as a fixative.
- If there is blood or mucus, that should be included in the stool. Because most of the pathogens are found in this substance.
- Exam the stool before giving antibiotic or other drugs.
- Semi-formed stool should be examined within 60 minutes of collection.
- Liquid stool should be examined within the first 30 minutes.
- Solid stool should be examined within the first hour of collection.
- Trophozoites degenerate in liquid stool rapidly, so exam the stool within 30 minutes.
- In the case of constipated cases, use non-residual purgative on the night before the collection of the stool.
Stool preservatives are:
- Preservatives for the wet preparation are:
- 10% formol-saline for the wet preparation. This is best preservatives as it kills the bacteria and preserves the protozoa and helminths.
- Sodium acetate formalin.
- Methionate iodine formalin. This is a good preservative for the field collection of the stool.
- For staining use Polyvinyl alcohol.
- Avoid preservatives for the culture of stool.
- Usually three parts of the preservatives and one part of the stool.
- To evaluate the function and integrity of the GI tract.
- To rule out the presence of WBCs and RBCs.
- To find ova or parasites.
- To see the presence of fat for malabsorption syndrome.
- For screening of colon cancer.
- For asymptomatic ulceration of GI tract.
- Evaluate diseases in the presence of diarrhea and constipation.
- Summary of stool studies are done to evaluate:
- Intestinal bleeding.
- Inflammatory diseases.
- Different causes of diarrhea.
- The stool is examined:
- Gross Stool examination includes:
- Concretions (gallbladder stone rarely may be found).
- Microscopic examination includes:
- Presence of leukocytes (pus cells).
- Presence of Red Blood Cells.
- Ova and parasites.
- Presence of meat fibers and muscle fibers.
- Presence of fat.
- Yeast and molds.
- The chemical examination includes:
- Stool pH.
- Reducing substances.
- For occult blood.
- Presence of fat, carbohydrate, and proteins.
Normal components of the stool:
- Undigested food particles like:
- Vegetable cells.
- Vegetable fibers.
- Muscle fibers.
- Starch granules.
- Desquamated epithelial cells.
- Digestive tracts products like:
- Bile pigments products.
- Digested but not absorbed food.
- Products produced by the decomposition of the stool are:
- Various gases like H2S, CO2, and nitrogen.
The consistency of the Stool may be:
- Normal is soft and formed.
- Loosely formed stools.
- watery stools.
- Thin stools.
- Pellet-like stools.
- Dry or hard stools found in constipated patients.
- Puttylike stools.
- small round hard stool is due to habitual constipation.
- Pasty stools are due to high-fat contents and seen in:
- common bile duct obstruction.
- Celiac disease. stool looks like aluminum paint.
- Cystic fibrosis due to pancreatic involvement and are greasy.
- Diarrheal stools are watery.
- Steatorrhea stool is:
- Large in amount.
- Foul smelling.
- Constipated stools are firm and may see spherical masses.
- Ribbon-like stool suggests the spastic bowel, rectal narrowing, stricture, or partial obstruction.
- The very hard stool is due to excessive absorption of water due to prolonged contact with colonic mucosa.
- Normal color is due to the presence of stercobilinogen.
- Yellow or yellow-green color is seen in diarrhea.
- Black and tarry (related with consistency) stools are due to bleeding of upper GI tract from tumors.
- Maroon or pink color is from lower GI tract due to tumors, hemorrhoids, fissure, or inflammatory process.
- Clay-colored stools are due to biliary tract obstruction.
- Mucous in the stool indicate constipation, colitis or malignancy.
- Pale color with greasy appearance is due to pancreatic deficiency leading to malabsorption.
|The color of the stool||Causes|
|1. Brown, dark brown or yellow-brown||Normal color is due to oxidation of bile pigments.|
|2. Gray color||Ingestion of chocolate or Cocoa. steatorrhea.|
|3. Green color||Ingestion of spinach, and chlorophyl vegetables, administration of calomel.|
|4. Black (Tary black)||Iron or bismuth ingestion, bleeding from the upper GI tract.|
|5. Very dark brown||Diet high in meat.|
|6. Red color||Diet high in beats, laxatives of vegetable origin, Bleeding from lower GI tract.|
|7. Green or yellow-green||Diet high in spinach, green vegetables.|
|8. REd streaks of blood on feces||Bleeding from the hemorrhoids, fissure, ulcerative lesion or carcinoma of rectum or anus.|
- Normally there is 100 to 200 G/day.
- With vegetable diet may be 250 g/day.
- Many disorders cause large, bulky stools even in people who don’t eat a lot.
- Like malabsorption syndrome, and carbohydrate indigestion.
- The size of your stools has more to do with how well you digest your foods than how much you eat.
- Some types of foods produce larger stools because they don’t break down completely.
- Some gastrointestinal disorders also cause poor food breakdown and absorption, which leads to large, bulky stools.
- The foul odor is caused by the undigested protein and by excessive intake of carbohydrate.
- Stool odor is caused by indole and skatole which are formed by the bacterial fermentation and putrefaction.
- A bad odor which is sickly produced by undigested lactose and fatty acids.
- The odor is increased due to excess intake of proteins.
- The putrid odor is due to severe diarrhea of malignancy or gangrenous dysentery.
- Mucous is produced by the mucosa of the colon in response to parasympathetic stimulation
- Pure mucous is translucent gelatinous material clinging to the surface of the stool. This may be seen in:
- Severe constipation.
- Mucous colitis.
- Excessive straining of the stool.
- emotionally unstable patient.
- Mucous in diarrhea with microscopically present with RBCs and WBCs is seen in:
- Bacillary dysentery.
- Ulcerative colitis.
- Intestinal tuberculosis.
- Acute diverticulitis.
- ulcerating malignancy of the colon.
- Mucus with blood which is clinging to stool is seen in:
- Malignancies of the colon.
- Inflammatory lesion of rectal canal.
- An excessive amount of mucus seen in:
- Villous adenoma of the colon.
- This depends upon the dietary intake.
- Normally stool is slightly acidic or alkaline or neutral.
- pH is 7.0 to 7.5 depending on the diet.
- Newborn pH = 5.0 to 7.5.
- pH of the stool depends upon the diet and bacterial fermentation in the small intestine.
- Carbohydrate changes the pH to acidic while the protein breakdown changes to alkaline.
- Breastfed infants pH has a slightly acidic stool.
- Bottle fed infants have a slightly alkaline stool.
- pH stool test helps to evaluate carbohydrate and fat malabsorption.
- pH stool also helps to know disaccharidase deficiency.
- Alkaline (Increased pH) stool is seen in:
- Villous adenoma.
- Antibiotic therapy.
- Excess intake of proteins.
- Acidic (Decreased pH) stool seen in:
- Fat malabsorption.
- Disaccharidase deficiency.
- Carbohydrate malabsorption.
- Excess intake of carbohydrates.
- Precautions for pH estimation:
- Barium intake and laxatives change the pH.
- If the specimen is contaminated with the urine, will need to discard the sample.
- Please see details of Reducing substances in the stool on the following link.
- This is the preliminary examination to find the cause of diarrhea.
- Presence of Leukocytes Normally there are no WBCs.
- WBCs only appear in infection or inflammation.
- Their presence is important in case of diarrhea or dysentery.
- >3 WBCs /high field are seen in ulcerative colitis and bacterial infection.
- Greater numbers of WBCs indicate invasive pathogens.
- Virus and parasites don’t cause WBCs in the stool.
- Increased number of WBCs in the stool.
- Bacillary dysentery.
- chronic ulcerative colitis.
- salmonella infection.
- Yersinia infection.
- Invasive E.coli diarrhea.
- Fistula of anus or rectum.
- Localized abscess.
- Few WBCs are seen in amoebiasis.
- Also, WBCs are seen in typhoid.
- The absence of WBCs seen in some of the diarrhoeal conditions alike:
- Viral diarrhea.
- Drug-induced diarrhea.
- Amoebic colitis.
- Non-invasive E.coli diarrhoea.
- Parasitic infestation.
- Toxigenic bacterial infection.
- Presence of Red Blood Cells in the stool.Blood in the stool can be:
- Bright red from the bleeding in the lower GI tract.
- Maroon in color.
- Black and tarry from bleeding from the upper GI tract.
- Occult blood (not visible to the naked eye).
- Causes of blood in stool:
- Make smear from the mucus area or from the watery stool.
- Please see more details in the occult blood.
|Stool findings (Physical features)||Possible Causes|
|1. Diarrhea mixed with blood and mucous||Typhoid, Amoebiasis and large colon carcinoma|
|2. Diarrhea mixed with Pus and mucous||Ulcerative colitis, Salmonellosis, Intestinal tuberculosis, Shigellosis, Regional enteritis, and acute diverticulitis|
|3. Patty stool with high-fat contents||Cystic fibrosis and CBD – obstruction|
|4. Formed stool with attached mucous||Constipation, Mucous colitis, and excessive straining|
|5. Small, hard dark balls like||Constipation|
|6. Clay-colored, pasty and little odor||Bile duct obstruction, and barium ingestion.|
|7. Black, tarry, sticky, watery, voluminous||Upper GI tract bleeding, Noninvasive infections like Cholera, Staphylo.coccal food poisoning, and Toxigenic E. Coli and Disaccharidase deficiency|
- Ova and parasites. Normally there are no parasites or eggs in the stool sample.
- Multiple stool sample is needed to rule out the parasitic infestation, at least three consecutive days.
- An abnormal result means parasites or eggs are present in the stool. Such infections include:
- Roundworms: Ascaris lumbricoides.
- Hookworms: Necator americanus.
- Pinworms: Enterobius vermicularis.
- Whipworm: Trichuris trichiura.
- Tapeworms: Diphyllobothrium latum, Taenia saginata, and Taenia solium
- Protozoa: Entamoeba histolytica (an amoeba), and Giardia lamblia (a flagellate)
- Presence of Fat. The fat in the stool shows the possibility of :
- Deficiency of pancreatic digestive enzyme.
- Deficiency of Bile.
- Meat fibers. and muscle fibers are seen in the stool. Their presence show defect in the digestion.
- The increased amount of meat fibers are found in:
- Malabsorption syndrome.
- The increased amount of meat fibers are found in:
A pancreatic functional defect like cystic fibrosis