22 Imaging of Hollow Organs

Question 1

Determining the Diagnostic Value of Tests

• Sensitivity
• Specificity
• Positive predictive value
• Positive predictive value

Answer 1

• Sensitivity = true positive / (true positive + false negative)
  
  • The % of patients with the target disorder who have a positive test result
• Specificity = true negative / (false positive + true negative)
  
  • The % of patients without the target disorder who have a negative test result
• Positive predictive value = true positive / (true positive + false positive)
  
  • The % of tests with a positive result who have the target disorder (compared to a gold standard)
• Negative predictive value = true negative / (true negative + false negative)
  
  • The % of tests with a negative result who do not actually have the target disorder

Question 2

Principles of Imaging

• The resolution of a test relates to/
• Many variables come into play when determining resolution
• only relative values are given for resolution of each test, since/
• what should be factored into clinical decision making
• “need to know”

Answer 2

• The resolution of a test relates to the smallest distinguishable object that can be routinely detected.
• Many variables come into play when determining resolution
  
  • quality of equipment, state of the disease, abilities of the operators and interpreters, and most important, the other available clinical information.
• only relative values are given for resolution of each test, since the ability to detect or exclude disease with each of these tests varies greatly, depending on the disease being evaluated.
• cost, discomfort, and risk to patient should be factored into clinical decision making.
  
  • these values are relative and depend on many factors.
• “need to know”
  
  • patients, family, and colleagues should participate in the decision-making process when considering which diagnostic test to use in a particular situation.

Question 3

Diagnostic Tests:
Plain films (xrays) and CT scanning of abdomen (p.6)

• Plain films (xrays)
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk
• CT scanning of abdomen
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk

Answer 3

• Plain films (xrays)
  
  • Physical principle: X-ray photons
  • Relative resolution: Moderate
  • Relative cost: Low
  • Relative discomfort: None
  • Relative risk: Low
• CT scanning of abdomen
  
  • Physical principle: X-ray photons & motion
  • Relative resolution: High
  • Relative cost: Moderate
  • Relative discomfort: Low
  • Relative risk: Low

Question 4

Diagnostic Tests:
Magnetic resonance imaging and Ultrasound (p.7)

• Magnetic resonance imaging
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk
• Ultrasound
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk

Answer 4

• Magnetic resonance imaging
  
  • Physical principle: Nuclear magnetic resonance
  • Relative resolution: High
  • Relative cost: High
  • Relative discomfort: Low
  • Relative risk: Low
• Ultrasound
  
  • Physical principle: High frequency sound waves
  • Relative resolution: Low
  • Relative cost: Low
  • Relative discomfort: None
  • Relative risk: None

Question 5

Diagnostic Tests:
Endoscopy and Gastric emptying scan (p.8)

• Endoscopy
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk
• Gastric emptying scan
  
  • Physical principle
  • Relative resolution
  • Relative cost
  • Relative discomfort
  • Relative risk

Answer 5

• Endoscopy
  
  • Physical principle: Visible light
  • Relative resolution: High
  • Relative cost: High
  • Relative discomfort: Low
  • Relative risk: Moderate
• Gastric emptying scan
  
  • Physical principle: Radioactivity
  • Relative resolution: Low
  • Relative cost: Low
  • Relative discomfort: None
  • Relative risk: Low

Question 6

Plain Films (p.10-11)

• chest films and abdominal plain films
• obtained by/
  
  • Areas where the x-ray beam passes through easily are/
  • Areas where the beam does not easily pass are/
  • In between these two extremes/
  • Key concept
• normal chest film
  
  • includes/
  • The esophagus/
  • The gastroesophageal junction/
  • The stomach/
  • Variably/
  • a normal abdominal plain film is often referred to as/

Answer 6

• chest films and abdominal plain films are the oldest but still most widely used of all tests.
• obtained by passing an x-ray beam through the body and exposing film on the other side.
  
  • Areas where the x-ray beam passes through easily are darker, for example, air.
  • Areas where the beam does not easily pass are white, such as bone or metal.
  • In between these two extremes, soft tissues like the liver and pancreas will appear as varying levels of gray.
  • Key concept – air is black, soft tissue is gray, and bone is white
• _ normal chest film_
  
  • includes the lower neck, shoulders superiorly, and complete bilateral diaphragms inferiorly.
  • The esophagus passes posterior to the trachea down the midline of the chest.
  • The gastroesophageal junction is approximately where the diagrams meet.
  • The stomach can be identified by the gastric bubble just under the left diaphragm.
  • Variably, portions of the proximal small bowel, liver, biliary tree, and transverse colon can be seen on a chest film.
  • a normal abdominal plain film is often referred to as a “KUB” which is an acronym for Kidneys, Ureter and Bladder.

Question 7

Small Bowel Obstruction (p.12)

• The small bowel
  
  • normally contains/
  • when blocked/
• In an image of small bowel obstruction
  
  • the small intestine/
  • Normal amounts pf air/

Answer 7

• The small bowel
  
  • normally contains only small amounts air,
  • when blocked (stricture, adhesions, extrinsic compression, tumor), air entering from the stomach backs up along with fluid, resulting in dilation of the lumen.
• In an image of small bowel obstruction
  
  • the small intestine is severely dilated and fills the abdomen.
  • Normal amounts pf air in the colon can be seen along with the small bowel, which suggests that the blockage is somewhere in the distal small intestine.

Question 8

Transabdominal Ultrasound

• Ultrasound (US) imaging of the GI tract is primarily focused on/
• Solid and fluid-filled organs/
• Organs that contain air/
• Advantages
• Disadvantages

Answer 8

• Ultrasound (US) imaging of the GI tract is primarily focused on the abdomen and pelvis.
• Solid and fluid-filled organs such as the liver, gallbladder and pancreas are particularly well seen with this diagnostic exam.
• Organs that contain air are not well seen since the ultrasound signal is blocked once it encounters air, thus the stomach, small bowel and colon are not well visualized
• Advantages
  
  • no risk,
  • painless,
  • non-invasive,
  • inexpensive,
  • widely available.
• Disadvantages
  
  • quality is operator-dependent,
  • poor quality if patient is obese,
  • lower resolution than CT for lesions within soft tissue,
  • US beam blocked by any air-containing organ.

Question 9

Gallstones (p.13)

• Gallstones are better seen with/
• the US is particularly good when the density of adjacent objects/
• the density of bile in the gallbladder vs. a gallstone
  
  • the stone/

Answer 9

• Gallstones are better seen with trans-abdominal ultrasound that with any other imaging study, even high-resolution CT.
• the US is particularly good when the density of adjacent objects is very different.
• the density of bile in the gallbladder is much less than that of a gallstone.
  
  • the stone is so dense that it will block much of the US signal, resulting in a ‘shadow.’

Question 10

Computed Tomographic Scanning (p.15)

• Computed tomography (CT) is widely used to visualize/
  
  • It is not affected by/
  • There is a moderate to high exposure to/
• The esophagus wall and surrounding tissues/
  
  • still used to detect/
• endoscopic ultrasound/
• Soft tissue lesions which may impinge on the esophagus are well seen with/
• The addition of oral and intravenous (IV) contrast dyes/
• The liver, gallbladder, pancreas and small bowel are well seen with/
• Limitations of CT

Answer 10

• Computed tomography (CT) is widely used to visualize gastrointestinal organs.
  
  • It is not affected by air the way a US is and is relatively safe and widely available.
  • There is a moderate to high exposure to radiation and moderate cost
• The esophagus wall and surrounding tissues are well seen on CT of the neck and chest.
  
  • still used to detect lesions adjacent to the esophagus,
• endoscopic ultrasound has replaced CT in imaging the esophageal wall.
• Soft tissue lesions which may impinge on the esophagus are well seen with CT.
• The gastric wall and surrounding tissue such as blood vessels and lymph nodes are also well visualized with CT;
  
  • this too has largely been replaced with endoscopic ultrasound.
• The addition of oral and intravenous (IV) contrast dyes enhances the sensitivity and specificity of abdominal CT by delineating what is inside the lumen (oral contrast) and blood vessels (IV contrast).
• The liver, gallbladder, pancreas and small bowel are well seen with CT, better than any other single diagnostic test.
• Limitations of CT
  
  • radiation exposure,
  • patient must be motionless,
  • cost is greater than ultrasound and plain films,
  • allergy to IV dye and inability to take oral contrast may limit quality.

Question 11

Hepatoma (primary hepatic tumor) (p.16)

• the malignant lesion/
• The stomach/
• the oval-shaped kidneys/
• The vertebra/
• Computed tomography/
  
  • This image/
  • Computer technology then/

Answer 11

• the malignant lesion is darker (less radio-opaque) than the surrounding liver tissue because it is made up of a less dense tissue than the liver and/or has less perfusion with blood (IV contrast).
• The stomach is the large structure on the patient’s left (right side of image) filled with white-appearing oral contrast,
• the oval-shaped kidneys are visible in the posterior (bottom) and also appear white due to IV contrast.
• The vertebra is between the two kidneys and it too appears white but because of its high density, just as seen in plain films.
• Computed tomography uses the same technology has plain films but the source of the x-ray and the film are both moving in opposite directions (a tomogram).
  
  • This image is just a slice of the abdomen but with greater resolution.
  • Computer technology then analyzes and assembles the tomograms to produce the highest quality image possible with the available data.

Question 12

Virtual Colonoscopy (CT colography) (p.17)

• Virtual colonoscopy
• Size of polyps
• the technique is still only used/
• Recommendation for screening with CT colography

Answer 12

• Virtual colonoscopy
  
  • has promise of providing imaging of the colonic mucosal lining,
  • had the potential of substituting for colonoscopy for diagnostic and screening purposes.
• Size of polyps
  
  • adequate sensitivity for polyps greater than 5 mm,
  • colonoscopy is still required to remove polyps and lesions less than 5 mm are not reliably detected.
• the technique is still only used in special cases where a patient cannot safely tolerate a colonoscopy.
• Recommendation for screening with CT colography is every 5 years instead of every 10 for colonoscopy.

Question 13

Magnetic Resonance Imaging (MRI) (p.18)

• MRI
  
  • limited but increasing value in/
  • relies on/
  • useful in detecting/
• MRCP (magnetic resonance cholangio-pancreatography)
  
  • valuable in/
  • may be a viable/

Answer 13

• MRI
  
  • limited but increasing value in imaging of the GI tract, since it does not reveal detail in soft tissue well.
  • relies on variations in water density to distinguish one tissue from another, but most GI organs have about the same water density.
  • useful in detecting
    
    • hemochromatosis (iron deposition in the liver)
    • hemangiomas (vascular anomalies in the liver).
• MRCP (magnetic resonance cholangio-pancreatography)
  
  • valuable in imaging the bile ducts and pancreatic duct.
  • may be a viable screening exam, without the radiation exposure of CT colonography (virtual colonoscopy).

Question 14

Barium studies

• Barium
  
  • ?
  • After ingesting oral barium or receiving via an enema/
  • This may be done/
• Barium exams may be either/

Answer 14

• Barium
  
  • an oral liquid that is highly radio-opaque.
  • After ingesting oral barium or receiving via an enema, plain x-rays of the area of interest are taken from multiple perspectives.
  • This may be done dynamically using video fluoroscopy or still images similar to chest x-rays and abdominal films
• Barium exams may be either
  
  • single (barium alone)
  • double contrast (barium and air).
    
    • air is introduced after the barium.
    • This provides a double contrast between the radio-lucent air and the radio-opaque barium which is left coating the mucosa.

Question 15

Major types of barium studies

• Barium esophagram (barium swallow)
  
  • Area visualized
  • Example diseases
• Upper GI series
  
  • Area visualized
  • Example diseases
• Small bowel follow through
  
  • Area visualized
  • Example diseases
• Barium enema
  
  • Area visualized
  • Example diseases

Answer 15

• Barium esophagram (barium swallow)
  
  • Area visualized: Oropharynx, esophagus
  • Example diseases: Swallowing disorders, esophageal mass lesions, strictures, achalasia
• Upper GI series
  
  • Area visualized: Esophagus, stomach, duodenum
  • Example diseases: Esophageal and gastric mass lesions, stricture, ulcers, tumors
• Small bowel follow through
  
  • Area visualized: Duodenum, jejunum, ileum
  • Example diseases: Ulcer, mass lesions, Crohn’s disease
• Barium enema
  
  • Area visualized: Colon, distal jejunum
  • Example diseases: Colonic mass lesions, ulcers, colitis, obstruction, diverticulosis

Question 16

Barium Esophagram:
Esophageal stricture (p.20)

• ?
• due to/

Answer 16

• narrowing of the mid-esophagus with some dilation of above.
• due to chronic reflux esophagitis with subsequent scarring of the esophageal mucosa and luminal narrowing.

Question 17

Barium Enema:
Colon cancer (p.21)

• ?
• recognized by/
• This indicates that barium/
• Mucosal neoplasms/

Answer 17

• mass lesion found on barium enema.
• recognized by a ‘filling defect.’
• This indicates that barium did not fill that area because something is displacing it.
• Mucosal neoplasms – polyps and cancer – are important causes for a filling defect.

Question 18

Principles of endoscopy (p.22)

• Since the introduction of flexible endoscopy and widespread availability, the use and clinical utility/
  
  • It is used for/
  • it has played a major role in/
• The modern videoendoscope is the result of years of research and development beginning with relatively barbaric rigid tube-like scopes that required/
  
  • These devices could only/
• Hinged devices with mirrors and integrated light sources/

Answer 18

• Since the introduction of flexible endoscopy and widespread availability, the use and clinical utility of this minimally invasive procedure has grown exponentially.
  
  • It is used for both diagnostic and therapeutic interventions
  • it has played a major role in understanding the pathogenesis and natural history of luminal GI diseases.
• The modern videoendoscope is the result of years of research and development beginning with relatively barbaric rigid tube-like scopes that required severe extension of the neck to pass
  
  • These devices could only visualize what was directly in front of the tip.
• Hinged devices with mirrors and integrated light sources were a considerable improvement but not until fiberoptic technology was perfected could scopes become truly flexible and safe.

Question 19

Types of endoscopes commonly used to examine the luminal GI tract

• Upper endoscope
• Duodenoscope or ERCP scope (endscopic retrograde cholangiopancreatography)
• Small bowel enteroscope
• Balloon enteroscope
• Capsule endoscope
• Cholangioscope
• Anoscope (rigid)
• Sigmoidoscope
• Colonoscope

Answer 19

• Upper endoscope – upper GI tract to the 3rd portion of the duodenum
• Duodenoscope or ERCP scope (endscopic retrograde cholangiopancreatography) – side-viewing tip, upper GI tract the 3rd portion of the duodenum with instruments to allow injection of contrast into biliary and pancreatic ducts
• Small bowel enteroscope – upper GI tract to the mid-jejunum
• Balloon enteroscope – from upper GI tract to mid and distal jejunum; from retrograde approach (via colon) distal jejunum and ileum
• Capsule endoscope – esophagus, entire small intestine, limited colon
• Cholangioscope – small diameter scope which fits through the ERCP scope and is inserted into the bile ducts
• Anoscope (rigid) – anal canal and distal rectum
• Sigmoidoscope – lower GI tract to the splenic flexure
• Colonoscope – lower GI tract to the terminal ileum

Question 20

Endoscopes

• Beyond direct visualization, endoscopes/
• Common examples using either upper endoscopy or colonoscopy to perform:

Answer 20

• Beyond direct visualization, endoscopes can add to the clinical management of GI diseases by using their therapeutic & diagnostic capabilities.
• Common examples using either upper endoscopy or colonoscopy to perform:
  
  • biopsy,
  • snare polyp removal,
  • mucosectomy (removing mucosal layer of tissue),
  • injection therapy,
  • electro and thermal cautery,
  • stent placement,
  • foreign body removal,
  • banding of varices,
  • dilation of strictures.

Question 21

Upper Endoscopy:
Gastroesophageal reflux disease (GERD) (p.24)

• Upper endoscopy is useful in evaluating patients with suspected GERD when/
• A normal esophagus/
• In GERD, the mucosa and underlying tissue/
• The image shows/
• The diameter of the lumen/
• Dilation with balloons and plastic tapered dilators and/or treatment of the underlying disease will/
• Formation of Barrett’s esophagus
  
  • should be suspected in any patient with/
  • requires/

Answer 21

• Upper endoscopy is useful in evaluating patients with suspected GERD when
  
  • the diagnosis is in question,
  • the symptoms are severe (daily, painful, not responding to therapy),
  • complications are suspected (bleeding, stricture, or Barrett’s formation).
• A normal esophagus has a glistening, pale pink appearance with blood vessels clearly visible through the mucosal lining.
• In GERD, the mucosa and underlying tissue is damaged from chronic exposure to gastric contents resulting in edema > inflammation > erosions > ulceration > scarring > stricture.
• The image shows linear ulcers running along the length of the esophagus with areas of erythema and loss of the vascular pattern, indicating edema and inflammation.
• The diameter of the lumen is beginning to narrow (stricture) due to circumferential scarring.
• Dilation with balloons and plastic tapered dilators and/or treatment of the underlying disease will reverse the damage and the condition typically resolves completely.
• Formation of Barrett’s esophagus
  
  • should be suspected in any patient with severe esophagitis
  • requires repeat endoscopy and biopsy to exclude dysplasia.

Question 22

Colonoscopy:
Colon polyps (p.25)

• the association of colonic polyps and colon cancer has resulted in /
• The images of a colon polyp
  
  • The base of the polyp was grasped with/
  • Electrocautery is applied to the snare, resulting in/
  • Complete removal and low risk of recurrence is possible because/
  • Malignant lesions that have extended beyond the muscularis mucosa have/

Answer 22

• the association of colonic polyps and colon cancer has resulted in
  
  • _​_widespread screening program to detect and remove polyps and early malignancies,
  • dramatic decreases in rates and mortality from colon cancer in the populations being screened.
• The images of a colon polyp
  
  • The base of the polyp was grasped with a snare device that was passed through a channel in the colonoscope and controlled by the operator externally.
  • Electrocautery is applied to the snare, resulting in both cutting and coagulation of the polyp base.
  • Complete removal and low risk of recurrence is possible because benign and early malignant polyps are localized to the mucosa.
  • Malignant lesions that have extended beyond the muscularis mucosa have a much poorer prognosis and cannot be excised endoscopically.