GI Imaging Flashcards
GI Imaging
Modalities
- X-Ray/ Radiograph
-
Fluoroscopic procedures
- Barium swallow
- Upper GI study / Small bowel follow through
- Contrast enema
- Ultrasound (US)
- Nuclear medicine/Meckel scan
- Computed tomography (CT)
-
Magnetic resonance imaging (MR)
- MR Enterography
Abdominal XR
Overview
- Use beams of energy that pass through body tissues onto a special film
- Structures appear different based on XR absorption
- Air containing structures ⇒ black
- Bone and metal ⇒ white
- Easily available test
Abdominal XR
Views
Can be obtained w/ pt:
- Supine view ⇒ lying flat w/ exposure from above
-
Erect/Upright view ⇒ standing up
- Can see fluid levels
- Stomach ⇒ always except if supine
- Small bowel ⇒ 2-3 levels possible
- Large bowel ⇒ none normally
- Can see fluid levels
-
Cross table lateral view ⇒ lying flat w/ exposure from the side
- Left side down
≥ 2 views ⇒ obstruction series

Abdominal XR
Indications
Baseline study for eval of:
- GI sx such as vomiting, abdominal pain, distention, constipation, diarrhea, etc
-
Common GI disorders:
- Intestinal obstruction
- Constipation
- Appendicitis
- Colitis
- Inflammatory bowel disease
- Abdominal mass
- Pneumatosis/Pneumoperitoneum
- Foreign body ingestion
- Feeding tube placement
Abdominal XR
Features
- Bowel gas pattern
- Free/Extra luminal air
- Soft tissue masses
- Calcifications
- Lung bases
- Osseous structures
Abdominal XR
Normal Anatomy
- Solid organs ⇒ soft tissue density
- Air containing structures (stomach and bowel) ⇒ black
- Bone ⇒ white
-
Small bowel ⇒ central
- Contains valvulae which extend across the lumen
-
Large bowel ⇒ peripheral
- Has haustral markings
- Contains stool

Normal
Bowel Gas Pattern
- Stomach bubble ⇒ LUQ
-
Small bowel
- Contains air throughout
- Normal caliber < 2.5 cm
-
Large bowel
- Air in rectum or sigmoid normally
- Air in the rectum mitigates against obstruction

Abnormal
Bowel Gas Patterns
-
Functional ileus
- Localized ileus (Sentinel loops)
- Generalized adynamic ileus
-
Mechanical obstruction
- Small bowel obstruction (SBO)
- Large bowel obstruction (LBO)
Localized Ileus
- Seen as sentinel loops on XR
- One or two persistently dilated loops of small or large bowel
- Gas in rectum or sigmoid
-
Location of sentinel loop is indicative of the underlying abnormality:
- RUQ ⇒ cholecystitis
- RLQ ⇒ appendicitis
- LUQ ⇒ pancreatitis or ulcer
- LLQ ⇒ diverticulitis

Generalized Ileus
Term describes diffusely dilated small and large bowel
-
Ileus = stasis of bowel contents
- Paralytic or adynamic
- See gas in dilated small and large bowel to the rectum
- Common in the postop setting
- Bowel sounds absent or hypoactive

Obstructive
Bowel Gas Pattern
-
Asymmetric caliber of bowel loops
- Loops proximal to obstruction ⇒ dilated
- See dilated loops of small bowel
- Loops distal to obstruction ⇒ compressed or airless
- Paucity of bowel gas distally
- Loops proximal to obstruction ⇒ dilated

Pneumoperitoneum
Free intraperitoneal air
-
XR findings:
- Air beneath diaphragm
- Air outlined against liver/flank
- Multiple other signs possible
-
Causes
- Rupture of hollow viscus
- Not perforated appendicitis
- Ulcer
- Tumor
- Trauma
- Instrumentation
- Post-op (expected up to 5-7 days)
- Necrotizing enterocolitis (Neonatal setting)
- Rupture of hollow viscus

GI Fluoroscopy
Overview
Provides dynamic assessment of the GI tract
-
Upper GI Tract
-
Barium swallow/Esophagram
- Upper GI tract coated w/ barium
- See & assess anatomy and function of esophagus, stomach, and duodenum
- Detect inflammation, hiatal hernias, scarring, blockages, intestinal malrotation and volvulus
- Upper GI study w/ or w/o small bowel follow through
-
Barium swallow/Esophagram
-
Lower GI Tract
-
Contrast Enema
- Water-soluble contrast introduced from below via a tube
- Helpful in evaluating colon for polyp, tumor, inflammatory bowel disease
-
Contrast Enema
Barium Swallow
- Used to visualize the pharynx and esophagus
- Pt swallows liquid barium while XR images are obtained
- Can be used for:
- Dx of food impaction and esophageal FB
- Esophageal cancer
- GERD / hiatal hernia
Hiatal hernia shown in image on left. Esophageal reflux shown on right.

Upper GI Study
- XR used to visualize stomach and small bowel
-
Duodenal sweep is assessed
- 1st, 2nd, 3rd and 4th components
- Normal location of duodeno-jejunal junction is left of spine @ level of duodenal bulb
Normal anatomy of stomach and proximal small bowel

Small Bowel Follow Through
- Images of abdomen & pelvis obtained after upper GI study
- Useful fo suspected abnl of small bowel
- Stricture
- Ulcer
- Neoplasm
Normal small bowel follow through

Water Soluble Contrast Enema
- Dynamic evaluation of the colon performed under fluoroscopy
- Rectal infusion of contrast
- Can demonstrate polyps, colon cancer, fistulas, ulcers, stenosis etc.

Abdominal US
Overview
- Utilizes sound waves
- Real time assessment
-
Advantages of US
- Safe
- Widely available
- No ionizing radiation
- Cheaper compared to CT/MR
Abdominal US
Indications
- Pyloric stenosis
- Acute appendicitis
- Intussusception
- Inguinal hernia
- US helps in real time evaluation of bowel peristalsis
- Screening examination for palpable abdominal mass
Ex. pyloric stenosis on US

Meckel’s Diverticulum
- Remnant of the omphalomesenteric duct
- Can cause bleeding (when contains ectopic gastric mucosa), intussusception, bowel obstruction or perforation
-
Rule of 2’s:
- Incidence 2% of general population
- Within 2 feet of ileocecal valve
- Most have clinical sx before age 2 years
- Approximately 2 inches in length (inflammatory mass may be much larger)

Meckel’s Scan
- Technetium-99m (99mTc) pertechnetate scan ⇒ Nuclear Medicine test
- Look for presence of ectopic gastric mucosa in the large bowel
- Test of choice to dx Meckel’s diverticula in children
- Scan detects gastric mucosa ⇒ ~ 50% of symptomatic Meckel’s diverticula have ectopic gastric or pancreatic cells contained within them
- Classic appearance ⇒ focal accumulation in RLQ
- Coincident w/ and as intense as gastric uptake
- ↑ in visibility w/ time
- In children, scan is highly accurate and noninvasive
- 95% specificity and 85% sensitivity

Abdominal CT
Overview
- Major imaging modality to assess bowel disease
- ± IV contrast
- Oral contrast preferred if assessment of bowel disease is needed
- Con is ionizing radiation
CT, IV contrast alone

Abdominal CT
Indications
- Abdominal pain
- Intestinal obstruction
- Acute appendicitis
- Diverticulosis/Diverticulitis
- Colitis
- Inflammatory bowel disease
- Oral contrast indicated
- Abdominal mass
CT w/ oral contrast seen in intestines

Abd CT
Acute Perforated Appendicitis

Abdominal MRI / MRI Enterography
Indications
- Assessment of bowel disease
- Inflammatory bowel disease
- Crohn’s disease
- Ulcerative colitis
- Acute appendicitis
- Abdominal mass
Crohn’s Disease
Abd MR
There are inflammatory changes involving the terminal ileum w/ proximal small bowel dilatation.

Normal
Abdominal MR

Abdominal MRI
Pros/Cons
-
Advantages
- Superior contrast resolution
- No ionizing radiation
- Most important factor, esp. in pts w/ IBD who may require imaging during acute flares
-
Disadvantages
- Expensive
- Longer duration study
- Younger pts or pts who cannot lie still may need sedation/general anesthesia
- Not always readily available