[OS 206] E03-T03-Imaging of the GI System_compressed

Plain Films

• Abdominal X-rays include at least the hemidiaphragm and go below, primarily focusing on the liver, spleen, stomach, and intestines, but may include other organs.
• Pelvis may or may not be included.
• Abdominal X-rays can be used to view KUB structures when the pelvis is not cut off.
• X-rays can be performed standing or supine.

Key Organs in Abdominal X-rays

• Liver: Located mostly in the Right Upper Quadrant, use liver vasculature to distinguish segments.
• Spleen: Located in the Left Upper Quadrant.
• The stomach is usually gas-filled and appears dark on X-rays.
• Kidneys: The right kidney is typically lower than the left; visibility improves with more perineal fat.
• Ribs are counted from the bottom up in Abdominal and KUB X-Rays.

KUB X-Ray

• A KUB X-ray includes the pelvis in the view.
• Focuses on the kidneys, ureters, and bladder, though GI organs might be visible.
• The psoas line should be visible.
• Usually done with the patient supine.

Organ Density

• Organ density affects imaging by altering how the X-ray is absorbed.
• Gas/air-filled organs appear radiolucent (black).
• Muscles, fat, solid organs have varying shades of gray depending on density.
• Dense structures appear radiopaque (white).
• Examined solid organs include the liver and spleen

Plain Films: Extraluminal Air

• Usual causes of extraluminal air include: rupture of a hollow viscus, perforated ulcer/diverticulitis/carcinoma, trauma/instrumentation, or post-op (5-7 days)
• Seldom seen in perforated appendix

Pneumoperitoneum

• Pneumoperitoneum involves air beneath the hemidiaphragm.
• On a left lateral decubitus view, air outlines the liver.
• Rigler's Sign: Occurs when air inside and outside the bowel lumen outlines walls
• The sign is visible as a thin line outlining the bowel borders.
• Delineation between two bowel areas indicates air presence in the abdominal cavity.
• Delineation appears as a double-folded delineation.

Football Sign

• Massive pneumoperitoneum causes gas outlining the abdominal cavity.
• Creates a football-like appearance.
• The falciform ligament appears similar to sutures of the football.
• In imaging, the liver can be seen with lucency representing the falciform ligament.

Calcification and Foreign Bodies

• Healthy organs are not readily seen in plain radiograph without abnormalities.
• Abnormal organs may be seen if there are calcifications present.
• The spleen must be usually the size of a kidney.

Conditions with Calcifications

• Abnormal pancreas - chronic pancreatitis
• Abnormal spleen - splenic calcifications

Important Anatomical Considerations

• The abdomen is covered by a peritoneum.
• Lymphatic pathologies (e.g. lymph node enlargement) can still be seen in an otherwise peritoneum cover
• Tabes Mesenterica: An old medical term for mesenteric lymph node tuberculosis/ Abdominal tuberculosis that primarily affects the lymph nodes of the mesentery.

Urolithiasis

• Indicates stones (or calculi) in the urinary tract

Nephrocalcinosis

• Indicates abnormal deposition of calcium salts in the renal parenchyma and tubules

Mercury/Coin Ingestion

• Ingested mercury appears radiopaque on imaging/ white dots
• If a coin has been ingested, it must be viewed in two angles
• Obstruction usually occurs in sphincter areas like the cricopharyngeal/lower esophageal sphincter or the ileocecal valve.
• This occurrence led to the banning of mercury thermometers given their fragile make

Soft Tissue Masses/Densities

• Plain films are poor in judging liver size.
• A normal liver should only extend up to the last rib
• Liver should only reach until the 12 ribs upon palpation in the clinics.

Hepatomegaly

• Hepatomegaly is observed where the liver extends beyond the iliac crest/bone.

Soft Tissue Masses/Densities

• Tumor or Cyst: Bowel Displacement, Paucity of gas, "Pad sign" extrinsic bowel
• Fluid Collections: Ascites, fluid collections with gas.
• Solid feel = mass (ovarian new growth); fluid feel = liquid collection (ascites).

Abscesses/Hematomas

• Can either be seen as lucencies or an increase in diameter of soft tissue.
• Gastrointestinal tract layers: oral → pharynx (closed off to the nasopharynx) → oropharynx → hypopharynx → cervical esophagus delineates the cricopharyngeus muscle that is at the level of C5-C6 → becomes thoracic esophagus once it reaches the thoracic inlet (T1) → hemidiaphragm → gastroesophageal junction after 1-2 cm.
• Two indentations pass through the heart -the left atrium and left bronchus.

Normal Bowel Gas Pattern

• GIT gas: Consists of swallowed air and bacterial production.
• Normally present in stomach, rectum, and sigmoid colon and is most recognizable in the stomach.
• Prone positioning is recommended to better view gas in rectum.
• Small bowel: Should have 2-3 loops of non-distended bowel

Important Measurements

• Normal small bowel diameter should be measured to <2.5-3.0cm
• The presence of >5 loops and a diameter >2.5 cm indicates obstruction.
• No obstruction or pathology yields a staggered picture of the bowels.
• Postprandial, gas and feces should be evacuated within 3-5 hours

Normal Air-Fluid Levels (AFL)

• Stomach always has air except in supine film
• Air rises and it will be be the only thing you see due to gravity
• Small bowel: 2 to 3 levels possibly
• Large bowel typically has no fluids
• Differences in AFL can indicate the stage of disease and what parts of the bowels are affected.
• Differences in AFL can indicate the stage of disease and what parts of the bowels are affected.
• Always with AFL in the stomach.

Differential vs. Non-differential AFL

• Differential AFL: Two distinct air-fluid interfaces on horizontal-beam abdominal radiographs that are at different heights but are within the same loop of the bowel.
• Non-differential AFL: All air-fluid levels are at the same height

Complete Abdominal Series

• Designed to visualize a 2D picture of the different portions of the abdomen.
• Assesses any gas or fluid levels within the abdominal cavity and the GIT
• Include supine, upright/left lateral decubitus, chest (upright/supine) and lateral rectum projections
• Consider that air goes up and fluid goes down
• Evaluating abdominal x-rays gives opportunity to evaluate the Chest

Abdominal Series: Supine

• Check type of gas pattern; non-obstructive vs obstructive.
• Check for calcifications and soft tissue masses

Abdominal Series: Upright

• Substitute: left lateral decubitus view; preferred due to air proximity with the liver for easier stomach/liver delineation
• Substitute: lateral rectum/For suspected obstruction given rectum is a retroperitoneal structure

Ileus and Obstruction

• Accumulation of air in the pointed quadrants indicates possible diagnosis of gallbladder/pancreatic problems or appendicitis
• Generalized Ileus Key Features: Gas in dilated small and large bowel and the rectum, long air-fluid levels and is seen in post-op patients

Mechanical Small Bowel Obstruction

• 3-5 hours: gas/fluid accumulation
• Dilated small bowel with AFL
• Early SBO may resemble localized ileus and should get follow-up

Mechanical Obstruction

• Causes of mechanical obstruction include: Intussusception

Small Intestinal Obstruction

• If obstruction is incomplete/early, gas is seen in the colon
• Complete & prolonged obstruction, no gas is seen in the lower bowel
• When the dilatation is large and filled from complete obstruction, ring-like structures are lost and becomes a dilated blood sausage.

Large Bowel Obstruction

• Dilated colon filled with mobile transverse colon
• Contrast is used to visualize by letting trace the system with media.
• Contrast media is barium which can assess obstruction and leaks.
• Barium is inert so the GI tract is not obstructed.
• Barium dipped in cotton may be swallowed by the patient. Caution that barium is an inert substance and can only be used if the GI tract is intact, lest any leak of barium will irritate the abdomen

Esophagogram

• Normal esophagus inserts behind the heart from the supraclavicular view through the esophageal-cardiac junction to stomach
• Lower esophageal sphincter blends in with the stomach.
• Imaging of a caustic esophageal stricture: Long segment involved (progressive luminal narrowing)
• Small Esophageal Ulcers Characterized by: Plaque-like vertically oriented lesions; Diffuse/long segments/ Ragged appearance and poor peristalsis
• Normal esophagus continues to a thinner constricted portion where a mass is assumed to be constricting (apple-core appearance

Achalasia

• Hypertonic lower esophageal sphincter, characterized by accumulation of barium
• There is accumulation of barium due to thin obstruction for bird's beak appearance on contrast media

Upper GI Series

• Stomach: Cardiac, fundus, body, antrum, and pylorus
• Divisions of the duodenum: duodenal bulb (start of the duodenum; divided in 4 parts).
• Resting gastric fluid forms a pool in the fundus beneath the diaphragm posteriorly and to the left (circular outline; gastric pseudotumor)
• To differentiate jejunum from ileum, draw a line from your liver to the pelvis: above is jejunum; below is ileum.
• Ulcer crater project outside the wall of the stomach for gastric ulcer.
• Hampton's line with the sign of undermining plus smooth collar/rim/edge indicative edema

Upper GI Small Intestine

• Small intestine wall thickness ~1-2mm
• Jejunum luminal diameter ≤ 3.5 cm
• Ileum luminal diameter ≤ 3 cm
• Jejunal folds do NOT disappear with distention while ileal folds will disappear

Cholangiography

• Imaging of the bile duct = biliary tree via radiograph
• Injected through T-tube into biliary tree
• Must be fasted or NPO/nothing by mouth

T-Tube Cholangiography

• Used to see contents if bile ducts are dilated in the procedure
• T-tube connects to the duodenum
• Biliary Tree should arborize but the splenic vein is visualised anterior to the
• Gallbladder.

Duodenal Ulcers

• Radiating folds lesions from the ulcer
• Ascariasis: Can also swallow the pigment

Foreign Bodies/Gastritis

• Assessed with contrast media opacifying Gallbladder to visualise with contrast from Ectopic origin not typically used
• santol seed lodging is the cecum
• Move patient into different orientations because it is more difficult to stones from air collection for the patient

Gallstones

• Choledocolithiasis - black entities/lucencies pointed by arrows within the biliary tree whitened by contrast + lots of gas bubbles
• Can document Santol seeds accumulated in the ileocecal area with multiple seed/obstruction.

Overview of abdominal x-rays, key organs, and KUB x-rays including the liver, spleen, stomach, and kidneys. Includes the position of organs and how they appear on x-rays. Ribs are counted from the bottom up.