Gastrointestinal System Lab Assignment 2 Answer Key
REFERENCE: Textbook unless otherwise stated
GASTROINTESTINAL BLEEDING AND DETECTION AND LOCALIZATION
1. List the reasons that an acute GI Bleed scan is performed. (Page 538)
a. Evaluate presence of a bleed and localize site of bleeding prior to treatment
2. What are the labeling efficiencies for in-vivo and in-vivo/in-vitro techniques? What is the advantage
of these techniques? (Page 539)
a. In-vivo: 60-90% labelling efficiency
b. In-vivo/in-vitro method: approaches 95% labelling efficiency
c. Absence of blood manipulation or risk of contamination
3. When there is an abundance of free pertechnetate secreted by the gastric mucosa and the kidneys,
what areas of the anatomy might be affected? (Page 539)
a. Interfere with ability to detect bleeding site in the stomach, proximal small bowel, colon
4. What is the advantage of using 99mTc-Sulfur Colloid for gastrointestinal bleeding? (Page 539)
a. 99mTc-sulfur colloid minimizes background activity and promotes high contrast ratios
5. What is the advantage of using 99mTc-RBC for gastrointestinal bleeding? (Page 539)
a. 99mTc-Tagged RBCs have prolonged retention in intravascular pool, which is better for
intermittent, slow GI bleeding; allow repetitive imaging up to 36 hours, lower radiation dose
to the liver and spleen, better detection of bleeding in the upper abdominal region
6. List the body structures that are normally seen during gastrointestinal bleeding imaging using both
radiopharmaceuticals. (Page 539 and Page 540)
a. 99mTc-Sulfur Colloid: early: intravascular space; later: liver, spleen, bone marrow, genitals
b. 99mTc-Tagged RBCs: great vessels of abdomen, kidneys, spleen, large/small bowel, genitals
7. List the instances that may lead to a false-positive result occurring when using both
radiopharmaceuticals. (Page 540)
a. 99mTc-Sulfur Colloid: renal transplants with rejection; asymmetrical bone marrow
accumulation of tracer (Paget’s, post-radiation therapy, tumor, etc.)
b. 99mTc-Tagged RBCs: anatomic variants of vascular structure
ECTOPIC GASTRIC MUCOSA
8. Most Meckel’s diverticula are asymptomatic, however ¾ of all symptoms that occur in children are
presented in what form? What other symptoms may be present? (Page 540)
a. Bleeding is ¾ of all symptoms in children; other symptoms include inflammation,
obstruction, intussusception, perforation of the bowel
9. What is the “Rules of 2” for Meckel’s diverticulum? (GI Lecture)
a. 2% of population; under the age of 2 years; within 2 feet of ileocecal valve; 2 inches in
length; 2 types of heterotrophic mucosa (pancreatic/gastric); and 2:1 male: female ratio
10. List the pharmacological agent that may be used during patient preparation to enhance the
probability of observing the ectopic gastric mucosa in a Meckel’s diverticulum. (Page 180)
a. Cimetidine/ Tagamet 20 mg/kg orally, 24 hours up to 1 hour before study
LIVER AND SPLEEN IMAGING
11. Liver and spleen imaging should be performed before administration of what contrast
agent? Why? (Page 542)
a. Iodinated or barium contrast- can result in artifactual defects of spleen or liver
