Feces

Feces It is the waste material passed out from the bowl through the anus. Feces is composed of the remaining digested / undigested food, water,bacteria and gastrointestinal tract secretions. Formation Of Feces; Chyme passes from the small intestine to the large intestine, as the chyme moves through the first half of colon large amounts of water and electrolytes is absorbed(when 9L of water fluids enter the intestine only 0.1L of water is excreted in feces since most of it is absorbed in the small intestine and 1/10 is absorbed in the large intestine.Water absorbtion transforms the chyme to a mush-like consistancy, then it moves to the transverse colon and it solidifies further and finally it passes the descending colon to the anus.

Composition of Feces; 1- Water 75%. 2-Solid 25%. a) Solidified components of the digestive juices,undigested fibers (e.g celluose) which is insoluble,acts as bowl irritant,draws water out into lumen,cleans out lower GIT and is correlated with lower risk of colon cancer. b) Dead bacteria (20%). c) Fat (10-20%). d) Inorganic material (10-20%). e) Undigested protein(2-3%).

Properties; Colour; Normal feces has a dark brown colour, (bilirubin in the presence of bacteria will get oxidized to urobilin which gives stool its typical colour) - Odor; The odor of feces is affected significantly by the type of food ingested and the bacterial flora of the individual (of the main order contributers H 2 S and mercaptens. - Consistency; Normal feces is solid to semi-solid depending on diet g/day.

Water and electrolytes; Electrolytes like bicarbonate are secreted by the wall of the large intestinal lumen, which helps to neutralize the acidic byproduct of bacterial metabolism. Na + and Cl - are absorbed by the intestinal wall which creats a concentration gradient that facilitates water absorbtion. The large intestine only absorbs 8L of water per day,the rest will remain in the colon giving feces a liquid consistency.

Bacteria; Bacteria in the colon, - Contributes to the formation and absorption of vit B 12,thiamin, riboflavin and vitamin K. - It digests cellulose producing nutrients that can be absorbed by the colon. - It produces gases such as CO 2, H 2 and methane which makes flatus (gas) thus contributing to feces ordor.

Fecal Analysis; Stool analysis is done to: Help identify diseases of the digestive tract, liver, and pancreas. Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help determine how well the pancreas is functioning. Help find the cause of symptoms affecting the digestive tract, including prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever. Screen for colon cancer by checking for hidden (occult) blood. Look for parasites, such as pinworms or Gardia Lamblia. Look for the cause of an infection, such as bacteria, a fungus, or a virus. Check for poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then checked for the fat and meat fibers. This test is called a 72-hour stool collection or quantitative fecal fat test.

Fecal Specimen collection; The patient is given a proper sample collection container,which is clean, dry, sealable and leak proof. The stool sample should not be contaminated with urine or water (urine can destroy protazoa). Fecal Analysis Methods; 1- Gross Examination ; The gross examination provides clues to possible GI disorders. a)Colour; Black colour may indicate old blood from the upper GIT, whereas bright red blood in feces indicates blood from the lower GIT. A very pale stool indicates biliary obstruction, or a barium sulfate enema.

The presence of blood streaked mucus or pus often accompanies bacterial or amebic dysentery. b)Consistancy ; A ribbon like fecal specimen could indicate irritable bowl syndrome or GIT obsruction. 2-Microscopic examination; a)Fecal leukocytes, especially neutrophils are associated with dysenttery. They can be detected by dried smears of the stool stained with gram stain.

Fecal leukocytes White blood cells in a stool sample stained with Methylene Blue

2-Microscopic examination; Meat fibers ; Increased undigested food such as meat fibers and vegetables correlate with mal digestion, and patients with hypermotility, pancretitis….. Increased meat fibers can be recognized microscopically as they are rectangular with the cross striations typical of muscle fibers.

3- Chemical analysis; a)Occulent blood, fecal blood is found in infection,trauma, colorectal cancer, ulcers hemorrhoids. Blood can be detected by many tests the best test is the guaiac impregnated paper in a card board holder.Patients should be instructed to avoid red meat, turnips, horse raddish, asprin, vitC as they interfere with the test.

guaiac test; A thin layer of feces is applied to a thick piece of paper attached to a thin film coated with guaiac. Both sides of the test card are peeled open, to access the inner guaiac paper. One side of the card is marked for application of the stool and the other is for the developer fluid.After applying the feces, one or two drops of hydrogen peroxide are then dripped on to the other side of the film, and it is observed for a rapid blue color change. When the hydrogen peroxide is dripped on to the guaiac paper, it oxidizes the alpha-guaiaconic acid to a blue colored quinone. When no blood or peroxidases,or catalases from vegetables are present this oxidation occurs very slowly.Heme found in blood catalyzes this reaction giving a positive result in two seconds. Therefore a positive result is one where there is a quick and intense blue color change of the film.

The guaiac test can often be false positive which is a positive test result when there is in fact no source of bleeding. This is particularly common if the recommended dietary preparation is not followed, as the heme in red meat or the peroxidase or catalase activity in vegetables, especially if uncooked, can cause analytical false positives. Vitamin C can cause analytical false negatives due to its anti-oxidant properties inhibiting the color reaction. Other tests for fecal blood include ; benzidine, orthotoluidine ……., but they are very sensitive thus they lead to many false positive results.

guaiac test; Both square test areas in the upper area of the card show the intense blue color of a positive result. The lower two smaller circular areas on the orange stripe are analytical control reactions, positive on the left and negative on the right, that help assure that the card and developer bottle have been maintained in proper conditions and have not been damaged before the test is performed

Fecal Analysis Methods; b) Fetal Hemaglobin ; Newborns may excrete stool containing blood. This could originate from the maternal blood ingested at delivery or from the newborns own GIT. Differentiating between these two sources of blood is important for the newborns survival. To determine whether it is fetal Hemoglobin (Hb F) or maternal Hemoglobin (Hb A). The stool is mixed with waterto yeild a pink supernatant. The supernatant is removed and then alkalinized with dilute NaOH, if the pink color remains, the blood contains fetal Hemoglobin (Hb F), if the pink color changes to yellow or brown within two minutes the Hb is maternal Hemoglobin (Hb A).

Fecal Analysis Methods; c)Fecal CHO ; Disaccharides are osmotically active and trigger movement of alarge amount of water to the intestines, when present in the colon.Fecal CHO are present in Celiac disease, and lactose intolerance. The CHO test is most useful in infants to diagnose chronic diarrhea cases which could be caused by e.g Celiac disease, and lactose intolerance. CHO in feces is detected by the Copper reduction test, to detect reducing sugars, if positive infant is tested by more specific serum tests. If CHO is present the pH of feces drops from pH 7 or 8 to a pH below 5.5.

Stool analysis Normal: The stool appears brown, soft, and well-formed in consistency. The stool does not contain blood, mucus, pus, harmful bacteria, viruses, fungi, or parasites.bacteria virusesfungi parasites The stool is shaped like a tube. The pH of the stool is about 6.pH The stool contains less than 2 milligrams per gram (mg/g) of sugars called reducing factors.milligrams Stool analysis

Abnormal: The stool is black, red, white, yellow, or green. The stool is liquid or very hard. There is too much stool. The stool contains blood, mucus, pus, harmful bacteria, viruses, fungi, or parasites. The stool contains low levels of enzymes, such as trypsin or elastase. enzymes The pH of the stool is less than 5.3 or greater than 6.8. The stool contains more than 5 mg/g of sugars called reducing factors; between 2 and 5 mg/g is considered borderline. The stool contains more than 7 g of fat (if your fat intake is about 100 g a day).