Ordering Stool Tests for Bowel Disorders | Blood & Stool

Fecal Matter

Order Tests

Human Feces

Stool assumes an important role in the differential diagnosis of disorders such as gastrointestinal infections, malabsorption syndromes, and inflammatory bowel diseases. Stool color varies greatly depending on the diet. The normal color of stool is tawny due to the presence of bilirubin and bile. Clay-colored or putty colored stool is observed in biliary obstructions. If more than 100 mL of blood is lost from the upper gastrointestinal system, black, tarry stool is observed. Besides bleeding, black-colored stool may be observed if patients receive treatment containing iron or bismuth. Red-colored stool is observed in lower gastrointestinal tract bleeding. We present the most up-to date information about stool tests that play an important role in the differential diagnosis and follow-up of gastrointestinal diseases. Specimens are examined for consistency (hard, formed, loose or watery) and for the presence of eye-catching abnormalities, such as a distinctive color, odor, worms, or pus. All fecal specimens must be properly labelled with the patient's name, age, sex, and the date of the sample collection. Multiple stool examinations are required before the presence of an infection is ruled out.

Normal Faeces Appear Brown and Formed or Semi Formed

Gross Examination of Fecal Matter

Many factors should be taken into account when ordering stool tests, including results from a physical examination, or results from a previous stool test.

Intestinal Malabsorption

The body requires a steady supply of nutrients to build, repair and maintain itself; to produce energy, enzymes, hormones, proteins, cells, tissues and bone, and to fight infections. Malabsorption can evolve to general malnutrition or to symptoms associated with deficiencies in specific nutrients. Nutrients are absorbed primarily by cells in the small intestines and are transported throughout the body. Interference with this process can lead to malabsorption. The severity of deficiencies seen depend on whether the problem affects general digestion and absorption or affects specific nutrients. Fat, proteins and carbohydrates cannot be properly digested without bile and pancreatic enzymes. Insufficiencies in these substances can occur with liver and pancreatic diseases that limit their production, or with conditions such as cystic fibrosis that prevent pancreatic enzymes from getting to the digestive tract. If the intestines are unable to or prevented from absorbing nutrients, then the nutrients are eliminated from the body in the stool. The most common signs and symptoms seen with general malabsorption include: diarrhea, loose and foul-smelling fatty stools (steatorrhea), abdominal pain, cramps, bloating, and gas. Other signs may be due to specific deficiencies caused by malabsorption. This may include: weakness, fatigue, dry and scaly skin, rash, glossitis, unexplained weight loss, muscle pain, bone pain, nausea, stomatitis and vomiting.

Common Digestive Problems

The passage of three or more motions a day is considered as diarrhoea. Diarrhoea increases the frequency, fluidity or the volume of bowel movement, which is relative to the usual habit of an individual. Faecal samples are best described by their colour, consistency and presence or absence of macroscopic blood or exudate. Dysentery is characterized by the passage of blood and mucus-stained stool, which is often associated with abdominal cramps and tenesmus. Bacterial agents are responsible for diarrhoea and dysentery. Gastroenteritis is caused by an inflammation of the mucus membranes of the stomach and the intestines, resulting in diarrhoea which is associated with vomiting. Feces should be checked for the presence of disease-causing microorganisms. Feces which is destined for microbiological examination is collected during the acute stage of the disease. About 20–40 grams of well-formed stool or 5–6 table spoonfuls of watery stool will suffice for a routine examination. The specimen must reach the laboratory within 60 minutes of passing of the stool, since the motile organisms, for example, Vibrio and amoebic trophozoites are heat sensitive and they can die or become unrecognizable after that period. Testing is often performed in steps with results leading to a diagnosis while ruling out other possible causes. A gastrointestinal pathogen panel simultaneously tests for viruses, bacteria and parasites that are common causes of digestive tract infections and diarrhea.

Symptoms Associated with Deficiencies in Specific Nutrients

Macroscopic Evaluation of Stool

The presence of a small amount of mucus in stool is normal. However, the presence of copious mucus or bloody mucus associated with abdominal cramps and tenesmus is abnormal — and often associated with bacillary and amoebic dysentery.

Common Pathogens

The type A enterotoxins of Staphylococcus aureus are most often incriminated in outbreaks of staphylococcal food poisoning. Bacillus cereus produces two types of toxins — one which causes diarrhoea and abdominal pain, and the other which causes nausea and vomiting. Clostridium perfringens causes gastroenteritidis which is characterized by diarrhoea and abdominal cramps. Clostridium difficle is associated with antibiotic associated diarrhoea and pesudomembrane colitis. Severe dehydration, vomiting, abdominal pain and acidosis associated with cholera are due to the action of the exotoxin of Vibrio cholera. E. coli (EPEC) neither produce toxins nor invade the gut mucosa, but have been implicated in diarrhoea in infants. E. coli (ETEC) produces a heat-labile enterotoxin (LT) and a heat stable enterotoxin (ST), that cause mild to severe diarrhoea in developing countries — an important cause of traveler's diarrhea. Shigella species cause bacillary dysentery. Salmonella spp (S. typhimurium and S. enteritidis) cause acute gastroenteritis which is characterized by self-limiting fever and diarrhoea. Campylobacter jejuni is the common cause of enteritis in most developing countries. Yersinia enterocolitica has been identified as an important cause of diarrhoea.

Intestinal Parasites

Entamoeba histolytica produces amoebic dysentery which is characterized by large, flask shaped ulcers which may get complicated into amoebic liver abscess and amoebic lung abscess. An infection with Giardia lamblia may lead to explosive watery diarrhoea, foul smelling stools and steatorrhoea. Cryptosporidium parvum, Isospora belli and Cyclospora cayetanensis have been recognized as important agents which are responsible for the watery diarrhoea in immunocompromised patients — particularly in those with HIV-AIDS. Balantidium coli produces dysentery which is transmitted by the ingestion of infective cysts in food and water or from hands which are contaminated with pig faeces. Ascaris lumbricoides has a world-wide distribution and its spread occurs by the faecal pollution of the environment. Trichuris trichiura can cause chronic diarrhea and intestinal ulceration with blood and mucus. Hookworm resides in the intestine and sucks blood, leading to iron deficiency anaemia and chronic blood loss. Taenia saginata and Taenia solium can produce a serious infection called neurocysticercosis, which causes epilepsy and other central nervous disorders. Enterobius vermicularis eggs cause intense irritation and scratching in the infected anal area.

Examination of Stool for Bacteria, Pathogens, and Parasites

Microscopic Findings in Stool

Since intestinal flora is greatly influenced by the diet, we lay emphasis on the importance of stool tests, in the diagnosis and follow-up of gastrointestinal disorders.