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This guide delves into the anatomy, physiology, and imaging techniques of the gastrointestinal system, covering key structures such as the mouth, esophagus, stomach, small intestine, large intestine, and accessory organs like the liver and gallbladder. It details gastric emptying studies, liver and spleen imaging, gallbladder functions, acute cholecystitis diagnosis, and GI bleeding causes. The document outlines the specific indications for imaging, patient preparation, and typical findings, making it a valuable resource for healthcare professionals involved in gastrointestinal diagnostics.
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NM 4203Scanning & Imaging Gastrointestinal System
Alimentary Canal • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine (colon)
Accessory Organs • Salivary glands • Pancreas • Liver • Gallbladder
Stomach Anatomy & Physiology • Three Regions: • Fundus : controls liquid emptying • Corpus (body) • Antrum : controls solid emptying
Gastric Emptying Study • Indications • Nausea, vomiting • Weight loss • Abdominal bloating • Mechanical causes • Ulcer, tumor, post-radiotherapy, pyloric stenosis, post-surgical • Nonmechanical causes • Diabetes, hypo or hypertension, neuropathy, gastroparesis, anorexia, amyloidosis
Gastric Emptying Study • Each lab must standardize meal type and size. • Solid phase could be meat, chicken liver, eggs, french toast, etc (99mTc Sulfur Colloid) • Liquid phase could be water, orange juice, apple juice. (111In DTPA)
Gastric Emptying Study • Patient fasting for at least 8 hrs. • Medium energy collimator (if doing liquid phase with In111DTPA) • Should eat meal within 5 minutes, followed by liquid.
Liver Anatomy & Physiology • Right upper quadrant of abdomen • Right lobe generally larger than left • Composed of: • Kupffer cells • Hepatocytes • Conversion of bilirubin to bile • Spleen: not part of the GI system
Liver – Spleen imaging • 99mTc Sulfur Colloid or 99mTc Albumin Colloid • Can do a flow (looking at vascularity of some defects) • No pt. prep • Static images 15 min. after injection • Anterior, RAO, Rt lat, RPO, posterior, LPO, Lt lat, LAO
Liver Hemangioma • 99mTc – Labeled Red Blood Cells • No pt. prep • Bolus 15 – 25 mCi with immediate flow imaging • Followed by pool images per facility protocol • SPECT usually 2-3 hours after injection.
Liver Hemangioma • Little or no blood flow to the lesion on early flow images • Delayed imaging usually shows increased uptake in hemangioma. • Other types of lesions will retain RBC’s, but only hemangiomas retain RBC’s for over 2 hrs. • Some consider this test to be 100% accurate for Hemangioma detection.
Gallbladder Anatomy & Physiology • Concentrates and stores bile • Stimulated by fatty meal to contract and release bile into the duodenum • Bile is useful to breakdown fats during digestion.
Hepatobiliary Imaging • Radiopharmaceuticals • 99mTc HIDA, 99mTc DISIDA, 99mTc Mebrofenin • Pt. should fast at least 2 hrs. before study, no more than 24 hrs. • Pain medications (opium or morphine based) should not be taken prior to imaging. • Rt. Lateral image is helpful to separate Gb (Gallbladder should be anterior to other structures)
Acute Cholecystitis • Usually due to cystic duct obstruction • Visualization of GB with radiopharmaceutical excludes diagnosis of acute cholecystitis • No GB visualized in 4 hrs, high probability of acute cholecystitis
Gallbladder Imaging: other medications • Cholecystokinin (CCK) • Causes gb contraction • Relaxes the sphincter of Oddi • Used for GB Ejection Fraction • Peptide hormone, naturally secreted by duodenum • Morphine • Decreases peristalsis • Constricts the sphincter of Oddi • Used when Gb is not visualized to “force” radiopharmaceutical into the gb.
Biliary Leak • Usually requested after surgery or trauma • Subtle leaks that may accumulate in the pelvis • May mimic a gb ~ labeled bile in the gallbladder fossa
Intestine anatomy & physiology • Small intestine • Duodenum, jejunum, and ileum • 20 feet long • Digestion and absorption of nutrients • Large intestine • Cecum, ascending colon, transverse colon, descending colon,sigmoid colon, and rectum. • Resorption of water
GI Bleed Imaging • Radiopharmaceutical • 99mTc Sulfur Colloid or 99mTc –labeled RBC’s (each facility may have different labeling method) • Bolus injection with immediate flow imaging
Causes of GI Bleeding • Diverticular disease • Angiodysplasia • Neoplasms • Inflammatory bowel disease • Not uncommon to never find a reason
Meckel’s Diverticulum • Common cause of GI bleeding in children. • Most are located in the ileum • 99mTc Pertechnetate ~ concentrates in gastric mucosa
Meckel’s Diverticulum • Painless rectal bleeding • More common in children • Some Meckel’s do not contain gastric mucosa, won’t show on scan • Glucagon – given i.v. 10 minutes after Tc injection or Zantac given i.v. prior to Tc injection • Decrease small bowel activity
Schilling Test • GI absorption of vitamin B12 • 57Co vitamin B12 given orally • Followed by IM injection of non-labeled vitamin B12 (saturates the liver) • Urine collected for 24 hrs.
