Stool Analysis

Clinical significance of stool analysis: Stool analysis is a series of tests done on stool (feces) samples for differential diagnosis of certain diseases of digestive system. Clinical significance of stool analysis: Diagnosis of digestive system infections: Bacteria, parasites, virus, and fungi. Diagnosis of pancreas disorders (inflammation); malabsorption of nutrients (fat). Primary screening test for some types of digestive system malignancy such as: colon cancer (occult blood). Primary screening for peptic ulcer disease, and some types of anemia (occult blood).

Which patients need urgent stool analysis? Patients with diarrhea. Patients with abdominal pain. Patients with anemia. Other patients for whom stool analysis is non-urgently required: Patients who is too thin or do not grow well. Patient with stool color that is changed to abnormal color.

Stool analysis procedure is divided into: Physical examination: Color Consistency Chemical examination: PH Sugar content. Fat content. Occult blood. Microscopic examination.

Physical Examination: Color: Normal feces is dark brown color (bilirubin in the presence of bacteria is oxidized to urobilinogen which is reduced to stercobilin which gives the stool its color). Abnormal Color: Black color: blood of upper GIT origin. Red color: blood of lower GIT origin. White color: yeast fermentation (Candida). Very pale color: biliary obstruction or barium (swallow or enema).

Normal feces is solid to semi-solid depending on the type of diet. Consistency: Normal feces is solid to semi-solid depending on the type of diet. Liquid stool indicates diarrhea (gastroenteritis). A ribbon like fecal specimen could indicate irritable bowl syndrome or GIT obstruction. Fatty stool indicates mal-digestion; Vitamins deficiency (A,D,E,K). N

Chemical Examination: The pH: The pH of the stool is 7.0-7.5 (low PH indicate carbohydrate malabsorption). Sugar contents: The stool contains less than 0.25 grams per deciliter (g/dL) or less than 13.9 millimoles per liter (mmol/L) of sugars. Elevated sugar indicates (more than 0.5g/dl): Lactose intolerance.

Fat contents: The stool contains 2-7 grams of fat /24h. High levels of fat in the stool may be caused by diseases such as pancreatitis, cystic fibrosis, or celiac disease (autoimmune allergy to gluten protein in wheat). Test: add 95% ethanolic-Sudan black-II stain or acetic acid to the specimen: 60 red droplets of neutral fats on HPF is considered fat malabsorption (steatorrhea). An inherited condition, affects the cells that produce mucus, sweat and digestive juices, causes the secretions to become thick and sticky. Most patients with cystic fibrosis (90-95%) have pancreatic enzyme insufficiency.

Hydrogen peroxide is then added Occult blood: Stool guaiac test : Stool applied to a paper surface with phenolic compound alpha-guaiaconic acid. Hydrogen peroxide is then added H2O2 oxidizes guaiaconic acid to dark-blue color within two seconds. Heme is a catalyst of this reaction. N

Clinical significance of the test: - Diagnosis of colorectal cancer. Patients should be instructed to avoid eating red meat, horse- radish, aspirin, or vitamin C as they interfere with the test by their catalases and peroxidases . Clinical significance of the test: - Diagnosis of colorectal cancer. - Diagnosis of ulcerative hemorrhoids. - Invasive gastroenteritis. N

Microscopic Examination: Fecal leukocytes, especially neutrophils are associated with dysentery. They can be detected by stool smears stained with gram stain. Parasites: Wet-mount smear (0.9% saline) or Iodine stained. Wet mount smear: Show the motility of active Protozoa. Iodine smear: Show the nucleus and karyosome of protozoa.

Protozoa: cysts and trophozoite Entamoeba histolytica. Giardia lamblia. Balantidium coli. Helminths: Ova ‘egg’: Schistosoma mansoni. Taenia worms Ascaris lumbricoides. Hook worms. Trichuris trichiura. Enterobius vermicularis. Larva: Strongyloides stercoralis.

Amoebic dysentery: Entamoeba histolytica (Rhizopoda) - Offensive stool. - Macroscopic: Feces mixed with blood and mucus. - Microscopic: RBCs, pus, mucus, and Entamoeba histolytica cyst or/and trophozoite (central karyosome). - Trophozoite show motility in one direction.

Entamoeba cyst (infective and diagnostic stage) Entamoeba trophozoite (diagnostic stage)

Entamoeba histolytica life cycle:

Giardia intestinalis Gastrointestinal Mastigophora. Habitat: Small intestine especially in duodenum. Disease: Fatty diarrhea especially in children. Morphology: Trophozoite: four pairs of flagella. Cyst.

Giardia cyst (infective and diagnostic) Giardia trophozoite (diagnostic stage).

Balantidial dysentery: Balantidium coli: - Ciliophora. - Kidney-shaped macronucleus and small micronucleus. - Ingestion of food and water contaminated by the cysts.

Helminths: Schistosoma mansoni: Trematoda. Intestinal bilharziasis. Diagnosis: finding of ova with lateral spine in the stool.

Taenia (Cestoda) infection: Taenia saginata (beef tapeworm). Taenia solium (pork tapeworm). Diagnostic stages: Gravid segments. Hexacantho-embryonated ova.

A pair of Taenia proglottids, dried and resembling sesame seeds, each containing hundreds of eggs

Ascaris lumbricoides: (Nematoda) Diagnostic stage: un-fertilized ova, fertilized, or embryonated ova. Adult stage. embryonated ova Fertile ova unfertile ova

Ascaris lumbricoides life cycle: N

Hook worms: Ancylostoma duodenale. Nematoda. Diagnostic stage: 4-8 cell embryonated ova. N

Enterobius vermicularis: -Nematoda. Diagnostic stage: D-shaped ova.

D-Shaped Ova

Trichocephalus trichiuris: n barrel shaped-egg  with two polar plugs

Strongyloides stercoralis: -Free-living Nematoda. -Diagnostic stage: Rhabditiform larvae in stool.

Stool analysis form: N