Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.
Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
For fecal occult blood testing, several (usually three) samples of stool are collected for testing. The reason for testing multiple samples is that bleeding from cancers and polyps often is intermittent and only one of the samples may show blood.
There are two types of fecal occult blood testing, 1) chemical and 2) immunologic.
Chemical testing: For chemical testing, a solution containing the chemical guaiac and an oxidizing chemical is used. If blood is present in the sample of stool, the mixing of the solution with blood causes the guaiac to turn visibly blue. The blue color is caused by the interaction (promoted by the oxidizing agent) of the heme portion of the
hemoglobin molecule, the oxygen carrying molecule in red blood cells, and the guaiac.
Immunologic testing:
For immunologic testing, a sample of stool is mixed with a solution that contains an antibody to globin, the protein part of the hemoglobin molecule. The antibody is combined with a small amount of gold. When the antibody/gold complex binds to the globin in stool, the antibody/gold/globin complex settles out of the solution as a visible line on the test strip.
How do the results of chemical fecal occult blood testing compare with immunologic fecal occult blood testing?
A chemical fecal occult blood test is inexpensive and easy, but it has several disadvantages.
Substances in fruits and vegetables can mimic heme and cause chemical fecal
occult blood tests to be falsely positive, that is, falsely abnormal. Therefore, it is necessary to restrict certain fruits and vegetables before and during the collection of stool samples.
Unlike heme which can travel intact from the stomach or small intestine and into the stool, globin is destroyed in the small intestine. As a result, a positive chemical
fecal occult blood test can be caused by bleeding anywhere in the stomach or intestines, but a positive immunologic
fecal occult blood test only occurs when there is bleeding into the colon. Therefore, it is necessary to restrict red meat containing hemoglobin before and during the collection of stool samples or the heme from the ingested meat will cause a falsely positive test.
Some drugs commonly cause small amounts of bleeding into the stomach or small intestine. Moreover, vitamin C and a few other drugs can cause an abnormal chemical
fecal occult blood tests. Therefore, these drugs must be stopped before and during the collection of samples.
The immunologic fecal occult blood test has additional advantages over the chemical
fecal occult blood test. First, it is more sensitive for blood. This means that given the same amount of blood in the stool, the immunologic
fecal occult blood test will more frequently be abnormal. In other words, it will more frequently detect cancers and precancerous polyps. Second, it is more specific for blood. That is, there will be fewer abnormal tests due to interfering substances in the diet, and as a result, an abnormal immunologic
fecal occult blood test will more commonly be due to cancer or a precancerous polyp. As a result, less follow-up testing (for
example, colonoscopy) will be necessary to pursue a falsely abnormal
fecal occult blood test.
Abdominal pain is pain in the belly and can be acute or chronic. Causes include inflammation, distention of an organ, and loss of the blood supply to an organ. Abdominal pain can reflect a major problem with one of the organs in the abdomen such as the appendix, gallbladder, large and small intestine, pancreas, liver, colon, duodenum, and spleen.
Rectal bleeding (hematochezia) refers to the passage of bright red blood from the anus. Rectal bleeding may be moderate to severe and most bleeding comes from the colon, rectum, or anus. Common causes include anal fissures, hemorrhoids, diverticulitis, and more.
Crohn's disease is a chronic inflammatory disease,
primarily involving the small and large intestine, but which can
affect other parts of the digestive system as well. Abdominal pain, diarrhea, vomiting, fever, and weight loss are
common symptoms.
Anemia is the condition of having less than the normal number of red blood cells or less than the normal quantity of hemoglobin in the blood. The oxygen-carrying capacity of the blood is, therefore, decreased.
Colon cancer is a malignancy that arises from the inner lining of the colon. Most, if not all, of these cancers develop from colonic polyps. Removal of these precancerous polyps can prevent colon cancer.
Ulcerative colitis is a chronic inflammation of the colon. Symptoms include abdominal pain, diarrhea, and rectal bleeding. Ulcerative colitis is closely related to Crohn's disease, and together they are referred to as inflammatory bowel disease. Treatment depends upon the type of ulcerative colitis diagnosed.
IBS (irritable bowel syndrome) is a common gastrointestinal disorder involving abnormal gut contractions (motility) characterized by abdominal pain,
bloating, mucous in stools, and irregular bowel habits with alternating diarrhea
and constipation, symptoms that tend to be chronic and to wax and wane over the
years. Treatment options include medication and lifestyle changes such as diet, exercise, and stress management to control symptoms. Also called spastic colitis, mucus colitis, nervous colon syndrome.
Dyspepsia (indigestion) is a functional disease in which the gastrointestinal organs, primarily the stomach and first part of the small intestine, function abnormally. It is a chronic disease in which the symptoms fluctuate infrequency and intensity. Symptoms of dyspepsia include upper abdominal pain, belching, nausea, vomiting, abdominal bloating, early satiety, and abdominal distention (swelling). These symptoms are most often provoked by eating.
Inflammation of the inner lining of the colon is referred to as colitis. Symptoms of the inflammation of the colon lining include diarrhea, pain, and blood in the stool. There are several causes of colitis including infection, ischemia of the colon, inflammatory bowel disease (Crohn's disease, Ulcerative colitis, or microscopic colitis). Treatment depends on the cause of the colitis.
A colon polyp is a benign tumor of the large intestine. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can easily be removed during colonoscopy and are not life threatening. If benign polyps are not removed from the large intestine, they can become malignant over time.
Gastritis is an inflammation of the stomach lining. Causes of gastritis include drinking too much alcohol, medications such as NSAIDs, ibuprofen, aspirin, H. pylori infection, severe infections, burns, anemia, and autoimmune disorders. Gastritis is diagnosed with endoscopy, blood tests, or stool tests. Treatment depends upon the cause of gastritis.
Digestion is the complex process of turning food you eat into the energy you need to survive. The digestive process also involves creating waste to be eliminated, and is made of a series of muscles that coordinate the movement of food.
Disease prevention in men includes routine screening tests that are part of basic prevention medicine. Take an active role in your own health care and discuss screening tests with your doctor early in life. Age of screening and timing of screening depends upon the condition being assessed.
Disease prevention in women includes screening tests that are a basic part of prevention medicine. All screening tests
are commonly available through your general doctor. Some specialized tests may be available elsewhere.
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