DIAGNOSTIC TESTS
I. LABORATORY TESTS
Laboratory tests for GI disorders include stool testing for blood (Hemoccult), other stool tests, and a variety of blood tests, such as hematocrit and hemoglobin for monitoring GI bleeding.
A. Hemoccult Guaiac Tests (Hemoccult)
Commercially available guaiac-impregnated slides or wipes present a simple, inexpensive, and aesthetically acceptable method of testing feces for blood.
Nursing and Patient Care Considerations
Advise patient as to the test preparation procedure. For 3 days before the test and during the stool collection period:
• Diet should have a high-fiber content.
• Avoid red meat in the diet.
• Avoid foods with a high peroxidase content, such as turnips, cauliflower, broccoli, horseradish, and melon.
• Avoid iron preparations, iodides, bromides, aspirin, NSAIDs, or vitamin C supplements greater than 250 mg/day.
• Avoid enemas or laxatives before the stool specimen collection.
NURSING ALERT
Certain protocols may specify to avoid aspirin and NSAIDs for at least 1 week before Hemoccult testing to prevent bleeding. Vitamin C (ascorbic acid) can cause a false-negative reading.
Procedure
• A wooden applicator is used to apply a stool specimen to the slide, or a special wipe is used and placed in the packet. Three stool samples are taken because of the possibility of intermittent bleeding and false-negative results.
• Slides (or wipes) applied inside a packet can be brought or mailed to the health care provider or laboratory.
• When hydrogen peroxide (denatured alcohol-stabilizing mixture) is added to samples, any blood cells present liberate their hemoglobin, and a bluish ring appears on the electrophoretic paper. Read precisely at 30 seconds.
• A single positive test is an indication for further diagnostic evaluation for GI lesions. False-positive results occur in about 10% of tests. Test may become false-negative in 10% of specimens tested 4 or more days after streaking on paper.
Community and Home Care Considerations
• Nonadherence to the diet/medication restrictions can cause false-positive or false-negative readings.
• The stool must not be contaminated with urine or toilet tissue.
• The stool guaiac specimen packets do not require refrigeration.
• Stool specimen packets should be submitted for laboratory testing within 6 days.
B. Stool Specimen
Advise patient as to the test preparation procedure. For 3 days before the test and during the stool collection period:
• Diet should have a high-fiber content.
• Avoid red meat in the diet.
• Avoid foods with a high peroxidase content, such as turnips, cauliflower, broccoli, horseradish, and melon.
• Avoid iron preparations, iodides, bromides, aspirin, NSAIDs, or vitamin C supplements greater than 250 mg/day.
• Avoid enemas or laxatives before the stool specimen collection.
NURSING ALERT
Certain protocols may specify to avoid aspirin and NSAIDs for at least 1 week before Hemoccult testing to prevent bleeding. Vitamin C (ascorbic acid) can cause a false-negative reading.
Procedure
• A wooden applicator is used to apply a stool specimen to the slide, or a special wipe is used and placed in the packet. Three stool samples are taken because of the possibility of intermittent bleeding and false-negative results.
• Slides (or wipes) applied inside a packet can be brought or mailed to the health care provider or laboratory.
• When hydrogen peroxide (denatured alcohol-stabilizing mixture) is added to samples, any blood cells present liberate their hemoglobin, and a bluish ring appears on the electrophoretic paper. Read precisely at 30 seconds.
• A single positive test is an indication for further diagnostic evaluation for GI lesions. False-positive results occur in about 10% of tests. Test may become false-negative in 10% of specimens tested 4 or more days after streaking on paper.
Community and Home Care Considerations
• Nonadherence to the diet/medication restrictions can cause false-positive or false-negative readings.
• The stool must not be contaminated with urine or toilet tissue.
• The stool guaiac specimen packets do not require refrigeration.
• Stool specimen packets should be submitted for laboratory testing within 6 days.
B. Stool Specimen
The stool is examined for its amount, consistency, and color. Normal color varies from light to dark brown, but various foods and medications may affect stool color. Special tests may be made for fecal urobilinogen, fat nitrogen, food residue, and other substances. Fecal leukocytes are tested by Wright’s stain, and stool cultures are obtained to identify bacteria, virus, or ova and parasites.
Nursing and Patient Care Considerations
• Use a tongue blade to place a small amount of stool in a disposable waxed container.
• Save a sample of fecal material if unusual in appearance, contains worms or blood, blood streaked, unusual color, or excess mucus; show to health care provider.
• Specimens for parasitology must be collected in vials containing special preservatives. For accurate specimen results, the vials must be sent to the laboratory as soon as possible. The vials should be refrigerated if unable to submit quickly to the laboratory.
• Send specimens to be examined for parasites to the laboratory immediately so the parasites may be observed under microscope while viable, fresh, and warm.
• Test for occult blood or to confirm grossly visible melena or blood—Hemoccult guaiac test.
• Consider that barium, bismuth, mineral oil, and antibiotics may alter the results.
Nursing and Patient Care Considerations
• Use a tongue blade to place a small amount of stool in a disposable waxed container.
• Save a sample of fecal material if unusual in appearance, contains worms or blood, blood streaked, unusual color, or excess mucus; show to health care provider.
• Specimens for parasitology must be collected in vials containing special preservatives. For accurate specimen results, the vials must be sent to the laboratory as soon as possible. The vials should be refrigerated if unable to submit quickly to the laboratory.
• Send specimens to be examined for parasites to the laboratory immediately so the parasites may be observed under microscope while viable, fresh, and warm.
• Test for occult blood or to confirm grossly visible melena or blood—Hemoccult guaiac test.
• Consider that barium, bismuth, mineral oil, and antibiotics may alter the results.
C. Hydrogen Breath Test
• The hydrogen breath test is used to evaluate carbohydrate absorption.
• A radioactive substance is ingested, and, after a certain time period, exhaled gases are measured.
• The test measures the amount of hydrogen produced in the colon, absorbed in the blood, and then exhaled in the breath.
• This test is used as a diagnostic test for short bowel syndrome, lactose intolerance, and bacterial overgrowth of the intestine (blind loop syndrome, Crohn’s disease, distal ileal disease).
Nursing and Patient Care Considerations
• The patient should be nothing-by-mouth (NPO) for 12 hours before the procedure.
• The patient should not smoke after midnight before the test.
• Antibiotics and laxative/enemas should not be used for 1 week before the test. These products may alter the laboratory results.
• Appropriate diet instructions should be given before discharge if the test is positive.
• The hydrogen breath test is used to evaluate carbohydrate absorption.
• A radioactive substance is ingested, and, after a certain time period, exhaled gases are measured.
• The test measures the amount of hydrogen produced in the colon, absorbed in the blood, and then exhaled in the breath.
• This test is used as a diagnostic test for short bowel syndrome, lactose intolerance, and bacterial overgrowth of the intestine (blind loop syndrome, Crohn’s disease, distal ileal disease).
Nursing and Patient Care Considerations
• The patient should be nothing-by-mouth (NPO) for 12 hours before the procedure.
• The patient should not smoke after midnight before the test.
• Antibiotics and laxative/enemas should not be used for 1 week before the test. These products may alter the laboratory results.
• Appropriate diet instructions should be given before discharge if the test is positive.
D. Helicobacter pylori Testing
• Laboratory tests for H. pylori include a serum immunoglobulin G antibody test and an H. pylori breath test.
• A positive antibody test may not differentiate between active and inactive disease.
• A negative test can be interpreted to mean no antibodies or antibodies present at a lower level than detectable.
Nursing and Patient Care Considerations
• Symptomatic patients and patients with an active or past history of ulcer disease should be tested for H. pylori. Endoscopy may be necessary for patients with symptoms of weight loss, anemia, occult blood loss, and patients older than age 50.
• It is recommended that negative H. pylori test results in a patient with ulcer-related complications be confirmed by a second test.
• Contact laboratory for the type of serologic test being performed for H. pylori and the appropriate tube for blood.
• Due to the potential for false-negative H. pylori breath test, preparation includes stopping treatment 2 weeks before testing.
• False-positive results from H. pylori breath testing may be caused by achlorhydria or urease production associated with other GI disorders.
• Laboratory tests for H. pylori include a serum immunoglobulin G antibody test and an H. pylori breath test.
• A positive antibody test may not differentiate between active and inactive disease.
• A negative test can be interpreted to mean no antibodies or antibodies present at a lower level than detectable.
Nursing and Patient Care Considerations
• Symptomatic patients and patients with an active or past history of ulcer disease should be tested for H. pylori. Endoscopy may be necessary for patients with symptoms of weight loss, anemia, occult blood loss, and patients older than age 50.
• It is recommended that negative H. pylori test results in a patient with ulcer-related complications be confirmed by a second test.
• Contact laboratory for the type of serologic test being performed for H. pylori and the appropriate tube for blood.
• Due to the potential for false-negative H. pylori breath test, preparation includes stopping treatment 2 weeks before testing.
• False-positive results from H. pylori breath testing may be caused by achlorhydria or urease production associated with other GI disorders.
II. RADIOLOGY AND IMAGING STUDIES
A. Upper GI Series and Small-Bowel Series
• Upper GI series and small-bowel series are fluoroscopic X-ray examinations of the esophagus, stomach, and small intestine after the patient ingests barium sulfate.
• As the barium passes through the GI tract, fluoroscopy outlines the GI mucosa and organs.
• Spot films record significant findings.
• Double-contrast studies administer barium first followed by a radiolucent substance, such as air, to produce a thin layer of barium to coat the mucosa. This allows for better visualization of any type of lesion.
Nursing and Patient Care Considerations
• Explain procedure to patient.
• Instruct patient to maintain low-residue diet for 2 to 3 days before test and a clear liquid dinner the night before the procedure.
• Emphasize nothing by mouth after midnight before the test.
• Encourage patient to avoid smoking before the test.
• Explain that the health care provider may prescribe all opioids and anticholinergics to be withheld 24 hours before the test because they interfere with small intestine motility. Other medications may be taken with sips of water, if ordered.
• Tell the patient that he will be instructed at various times throughout the procedure to drink the barium (480 to 600 mL).
• Explain that a cathartic will be prescribed after the procedure to facilitate expulsion of barium.
• Instruct the patient that stool will be light in color for the next 2 to 3 days from the barium.
• Instruct patient to notify health care provider if he has not passed the barium in 2 to 3 days because retention of the barium may cause obstruction or fecal impaction.
• Note that water-soluble iodinated contrast agent (such as Gastrografin) may be used for a patient with a suspected perforation or colonic obstruction. Barium is toxic to the body if it leaks into the peritoneum with perforation. It can also worsen an obstruction, thus is not used if an obstruction is suspected.
• Upper GI series and small-bowel series are fluoroscopic X-ray examinations of the esophagus, stomach, and small intestine after the patient ingests barium sulfate.
• As the barium passes through the GI tract, fluoroscopy outlines the GI mucosa and organs.
• Spot films record significant findings.
• Double-contrast studies administer barium first followed by a radiolucent substance, such as air, to produce a thin layer of barium to coat the mucosa. This allows for better visualization of any type of lesion.
Nursing and Patient Care Considerations
• Explain procedure to patient.
• Instruct patient to maintain low-residue diet for 2 to 3 days before test and a clear liquid dinner the night before the procedure.
• Emphasize nothing by mouth after midnight before the test.
• Encourage patient to avoid smoking before the test.
• Explain that the health care provider may prescribe all opioids and anticholinergics to be withheld 24 hours before the test because they interfere with small intestine motility. Other medications may be taken with sips of water, if ordered.
• Tell the patient that he will be instructed at various times throughout the procedure to drink the barium (480 to 600 mL).
• Explain that a cathartic will be prescribed after the procedure to facilitate expulsion of barium.
• Instruct the patient that stool will be light in color for the next 2 to 3 days from the barium.
• Instruct patient to notify health care provider if he has not passed the barium in 2 to 3 days because retention of the barium may cause obstruction or fecal impaction.
• Note that water-soluble iodinated contrast agent (such as Gastrografin) may be used for a patient with a suspected perforation or colonic obstruction. Barium is toxic to the body if it leaks into the peritoneum with perforation. It can also worsen an obstruction, thus is not used if an obstruction is suspected.
B. Barium Enema
• Fluoroscopic X-ray examination visualizing the entire large intestine is administered after the patient is given an enema of barium sulfate.
• Can visualize structural changes, such as tumors, polyps, diverticula, fistulas, obstructions, and ulcerative colitis.
• Air may be introduced after the barium to provide a double-contrast study.
Nursing and Patient Care Considerations
• Explain to the patient:
o What the X-ray procedure involves.
o That proper preparation provides a more accurate view of the tract and that preparations may vary.
o That it is important to retain the barium so all surfaces of the tract are coated with opaque solution.
• Instruct the patient on the objective of having the large intestine as clear of fecal material as possible:
o The patient may be given a low-fiber, low-fat diet 1 to 3 days before the examination.
o The day before examination, intake may be limited to clear liquids (no drinks with red dye).
o The day before the examination, a oral laxative, suppository, and/or cleansing enema may be prescribed.
• The patient will be NPO after midnight the day of procedure.
• An enema or cathartic may be ordered after the barium enema to cleanse bowel of barium and prevent impaction.
• Inform the patient that barium may cause light-colored stools for several days after the procedure.
NURSING ALERT
If barium enema and upper GI series are both ordered, the upper GI series is done last so barium traveling down the digestive tract does not interfere with the results of the barium enema.
• Fluoroscopic X-ray examination visualizing the entire large intestine is administered after the patient is given an enema of barium sulfate.
• Can visualize structural changes, such as tumors, polyps, diverticula, fistulas, obstructions, and ulcerative colitis.
• Air may be introduced after the barium to provide a double-contrast study.
Nursing and Patient Care Considerations
• Explain to the patient:
o What the X-ray procedure involves.
o That proper preparation provides a more accurate view of the tract and that preparations may vary.
o That it is important to retain the barium so all surfaces of the tract are coated with opaque solution.
• Instruct the patient on the objective of having the large intestine as clear of fecal material as possible:
o The patient may be given a low-fiber, low-fat diet 1 to 3 days before the examination.
o The day before examination, intake may be limited to clear liquids (no drinks with red dye).
o The day before the examination, a oral laxative, suppository, and/or cleansing enema may be prescribed.
• The patient will be NPO after midnight the day of procedure.
• An enema or cathartic may be ordered after the barium enema to cleanse bowel of barium and prevent impaction.
• Inform the patient that barium may cause light-colored stools for several days after the procedure.
NURSING ALERT
If barium enema and upper GI series are both ordered, the upper GI series is done last so barium traveling down the digestive tract does not interfere with the results of the barium enema.
C. Ultrasonography (Ultrasound)
• A noninvasive test focuses high-frequency sound waves over an abdominal organ to obtain an image of the structure.
• Ultrasound can detect small abdominal masses, fluid-filled cysts, gallstones, dilated bile ducts, ascites, and vascular abnormalities.
• Ultrasound with Doppler may be ordered for vascular assessment.
Nursing and Patient Care Considerations
• If indicated, prepare the patient before the procedure with a special diet, laxative, or other medication to cleanse the bowel and decrease gas.
• Abdominal ultrasound usually requires the patient to be NPO for at least 6 hours before the procedure.
• Change position of patient, as indicated, for better visualization of certain organs.
• A noninvasive test focuses high-frequency sound waves over an abdominal organ to obtain an image of the structure.
• Ultrasound can detect small abdominal masses, fluid-filled cysts, gallstones, dilated bile ducts, ascites, and vascular abnormalities.
• Ultrasound with Doppler may be ordered for vascular assessment.
Nursing and Patient Care Considerations
• If indicated, prepare the patient before the procedure with a special diet, laxative, or other medication to cleanse the bowel and decrease gas.
• Abdominal ultrasound usually requires the patient to be NPO for at least 6 hours before the procedure.
• Change position of patient, as indicated, for better visualization of certain organs.
D. Computed Tomography Scan
• This is an X-ray technique that provides excellent anatomic definition and is used to detect tumors, cysts, and abscesses.
• The computed tomography (CT) scan can also detect dilated bile ducts, pancreatic inflammation, and some gallstones.
• It identifies changes in intestinal wall thickness and mesenteric abnormalities.
• Ultrasound and CT can be used to perform guided needle aspiration of fluid or cells from lesions anywhere in the abdomen. The fluid or cells are then sent for laboratory tests (such as cytology or culture).
• A newer technique of focused appendiceal CT can be used to diagnose appendicitis.
o Rectal contrast media is given so the colon is opacified quickly without waiting for oral contrast to reach the appendix.
o The right lower quadrant is focused on to visualize the appendix, so the procedure is quick.
Nursing and Patient Care Considerations
• Instruct the patient that fasting for 4 hours before the procedure and an enema or cathartic may be necessary. This is to clean the bowel for better visualization.
• Ask the patient if she is pregnant. If yes, do not proceed with scan and notify health care provider.
• Ask if there are known allergies to iodine or contrast media. A contrast medium may be given I.V. to provide better visualization of body parts. If allergic, notify the technician and health care provider immediately.
• Instruct the patient to report symptoms of itching or shortness of breath if receiving contrast media, and observe patient closely.
CREDITS TO MR. RELIE CASTRO
• This is an X-ray technique that provides excellent anatomic definition and is used to detect tumors, cysts, and abscesses.
• The computed tomography (CT) scan can also detect dilated bile ducts, pancreatic inflammation, and some gallstones.
• It identifies changes in intestinal wall thickness and mesenteric abnormalities.
• Ultrasound and CT can be used to perform guided needle aspiration of fluid or cells from lesions anywhere in the abdomen. The fluid or cells are then sent for laboratory tests (such as cytology or culture).
• A newer technique of focused appendiceal CT can be used to diagnose appendicitis.
o Rectal contrast media is given so the colon is opacified quickly without waiting for oral contrast to reach the appendix.
o The right lower quadrant is focused on to visualize the appendix, so the procedure is quick.
Nursing and Patient Care Considerations
• Instruct the patient that fasting for 4 hours before the procedure and an enema or cathartic may be necessary. This is to clean the bowel for better visualization.
• Ask the patient if she is pregnant. If yes, do not proceed with scan and notify health care provider.
• Ask if there are known allergies to iodine or contrast media. A contrast medium may be given I.V. to provide better visualization of body parts. If allergic, notify the technician and health care provider immediately.
• Instruct the patient to report symptoms of itching or shortness of breath if receiving contrast media, and observe patient closely.
CREDITS TO MR. RELIE CASTRO
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