Digestive System Trivia

Patient Preparation, Contrast Media, and Pharmacology

  • Patient Fasting and Preparation:

    • When an Upper Gastrointestinal (UGI) series and esophagus examination are scheduled for the morning, food and fluids must be withheld starting after midnight, or for a duration of 8−9 hours8 - 9\text{ hours}.

  • Contrast Media Types for Upper GI:

    • Barium Sulfate: Standard positive contrast agent.
    • Gas-Producing Crystals: Used to produce carbon dioxide gas for double-contrast studies.
    • Water-Soluble Iodinated Contrast: Indicated whenever there is a suspected perforation or leak in the gastrointestinal tract.
    • Gastroview: A specific water-soluble, iodinated contrast agent with a bitter taste, utilized throughout the gastrointestinal tract when perforations are questionable.

  • Pharmacologic Agents:

    • Glucagon: Administered intravenously or intramuscularly before or during a double-contrast gastrointestinal examination to relax the smooth muscle of the gastrointestinal tract and significantly reduce gastrointestinal motility.

  • Double-Contrast Examination Advantages:

    • Superior visualization and detection of small mucosal lesions.
    • Enhanced demonstration and evaluation of the mucosal lining and rugae.

  • Barium Transit Timeline:

    • Under normal physiological conditions, barium sulfate takes approximately 24 hours24\text{ hours} to travel completely through the gastrointestinal tract and reach the rectum.

Esophageal Radiography and Maneuvers

  • Recommended Body Position:

    • The recumbent position is strongly recommended for radiographic imaging of the esophagus.
    • Physiological Rationale: Eliminates the acceleration of gravity, which slows transit and allows for more complete filling of the esophageal lumen, while facilitating easier visualization of esophageal varices.

  • Specialized Maneuvers and Positions:

    • Trendelenburg Position: The specialized body position best suited to demonstrate diaphragmatic herniations (hiatal hernias).
    • Valsalva Maneuver: The patient swallows barium while holding their breath and is then directed to bear down forcibly as if having a bowel movement. This maneuver increases intrathoracic and intra-abdominal pressure to distend the veins and demonstrate esophageal varices.

  • Standard Routine Projections:

    • A complete routine examination of the esophagus typically consists of:
    • Anteroposterior (AP) projection.
    • Right Lateral projection.
    • Oblique projection (performed upon request; the Right Anterior Oblique is standard).

  • Positioning and Centering Specifications:

    • Oblique Esophagus:
    • The recommended projection is the Right Anterior Oblique (RAO).
    • Patient body rotation ranges from 35∘−40∘35^\circ - 40^\circ.
    • Lateral Esophagus:
    • The midcoronal plane (MCP) is centered to the center of the radiographic table or vertical grid device.
    • Central Ray (CR) Centering Level:
    • The central ray is directed to the level of the thoracic vertebrae T5−T6T5 - T6.

Stomach and Upper Gastrointestinal Positioning

  • Respiration Phase:

    • All radiographic exposures of the stomach and intestines are recommended to be taken on suspended expiration to elevate the diaphragm and avoid compression of abdominal viscera.

  • Positioning for Specific Anatomical Demonstrations:

    • Anterior and Posterior Gastric Surfaces: The Right Lateral UGI position best demonstrates both the anterior and posterior surfaces of the stomach.
    • Duodenal Bulb and Pyloric Canal: The Right Anterior Oblique (RAO) position provides the best profile image of the pyloric canal, duodenal bulb, and C-loop of the duodenum in an average (sthenic) patient.

  • Centering Landmarks and Anatomical Vertebrae:

    • PA Projection of the Stomach:
    • The central ray is centered to the level of L1−L2L1 - L2.
    • The transverse point of entry is located halfway between the patient's left lateral border of the body and the midsagittal plane (MSP).
    • AP and PA Oblique Projections of the Stomach:
    • The image receptor (IR) and central ray are centered at the level of L1−L2L1 - L2.
    • Localization Methods: Positioned a hand's width above the iliac crest, approximately 1−2 inches1 - 2\text{ inches} above the lower rib margin, or halfway between the xiphoid process and the lower rib margin.
    • PA Oblique Transverse Entry: Enters midway between the vertebral column and the elevated lateral border of the abdominal wall at the level of L1−L2L1 - L2.
    • Lateral Projection of the Stomach:
    • The central ray enters at the level of L1−L2L1 - L2, midway between the midcoronal plane (MCP) and the anterior abdominal border.
    • Upright Modification:
    • If stomach or UGI images are requested with the patient upright rather than recumbent, centering must be adjusted downward by approximately 3−6 inches3 - 6\text{ inches} due to the inferior displacement of the viscera caused by gravity.

  • Degree of Obliquity by Body Habitus:

    • AP Oblique (LPO): Obliquity ranges from 30∘−60∘30^\circ - 60^\circ, with an average rotation of 45∘45^\circ.
    • PA Oblique (RAO): Obliquity ranges from 40∘−70∘40^\circ - 70^\circ.
    • Habitus Variations: Hypersthenic patients require the greatest degree of obliquity (70∘70^\circ) because the stomach lies high and transverse, requiring more rotation to separate the pylorus and duodenal bulb from the spine.

Contrast Distribution in Stomach Projections

  • Fluid Mechanics of Contrast Media:

    • In a double-contrast examination, heavier liquid barium sinks to dependent portions of the stomach, whereas radiolucent gas/air rises to fill non-dependent structures.

  • Fundus Contrast Contents by Projection:

    • PA Projection (Prone): Air fills the fundus (barium flows down into the body and pylorus).
    • RAO Projection (Prone Oblique): Air fills the fundus.
    • Right Lateral Projection (Recumbent): Air fills the fundus.
    • LPO Projection (Supine Oblique): Barium fills the dependent fundus.
    • AP Projection (Supine): Barium fills the dependent fundus (utilized as an alternative when a patient cannot lie prone on their stomach).

Small Bowel Radiographic Procedures and Administration

  • Administration Routes for Barium Sulfate:

    • Oral Ingestion: The patient drinks the barium suspension by mouth.
    • Barium Enema (Reflux): Retrograde administration where contrast is infused via the rectum and completely refluxed through the ileocecal valve into the small intestine.
    • Enteroclysis: Direct intubation of the small intestine via an enteroclysis tube placed into the duodenum or proximal jejunum, followed by high-flow administration of contrast.

  • Timing and Marker Protocols:

    • Radiographic tracking begins immediately; the initial small bowel image is typically taken 15 minutes15\text{ minutes} after the patient finishes drinking barium.
    • Time markers indicating the exact interval (e.g., 15 min15\text{ min}, 30 min30\text{ min}, 60 min60\text{ min}) are mandatory on all small bowel radiographs.

  • Centering Criteria:

    • For delayed radiographs of the small intestine, the central ray enters at the midsagittal plane (MSP) at the level of the iliac crests (L4−L5L4 - L5 interspace).

  • Procedure Termination:

    • The small bowel series is completed and radiographic exposures cease when the barium contrast column reaches the ileocecal valve and demonstrates the terminal ileum.