S11) Investigating the GI Tract

Question 1

What are the 5 different imaging modalities of the GI tract?

Answer 1

• Plain X-rays – AXR, CXR
• Contrast studies – Barium swallow, enema, meal/follow through, water soluble contrast studies
• Ultrasound
• Cross-sectional imaging – CT, MRI
• Angiography

Question 2

Why request an abdominal X-ray?

Answer 2

• Acute abdominal pain
• Small/large bowel obstruction
• Acute exacerbation of IBD
• Renal colic

Question 3

What are the features of an AXR?

Answer 3

• Air/gas
• Bowel
• Calcification (bone and stones)

Question 4

In terms of bowel gas patterns, what kind of structures are visible in an AXR?

Answer 4

• Visible if gas filled / gas and fluid filled
• Not visible is fully fluid filled

Question 5

The bowel gas patterns in an AXR varies according to transit time.

Describe this

Answer 5

• Slow transit = colon (faeces ± gas)
• Medium transit = stomach (fluid + lots of gas)
• Fast transit = small bowel (fluid)

Question 6

Identify 5 conditions which produce abnormal bowel gas patterns in an AXR

Answer 6

• Small bowel obstruction (>3 cm)
• Large bowel obstruction (>6 cm)
• Paralytic Ileus
• Volvulus
• Toxic Megacolon

Question 7

How does small bowel obstruction present?

Answer 7

• Vomiting (early)
• Distension (mild)
• Absolute constipation (late)
• Colicky pain

Question 8

What are the causes of small bowel obstruction?

Answer 8

• Adhesions
• Hernias (inguinal, femoral, incisional)
• Tumours
• Inflammation

Question 9

How does large bowel obstruction present?

Answer 9

• Vomiting (late, faeculant)
• Distension (significant)
• Pain
• Absolute constipation

Question 10

What are the causes of large bowel obstruction?

Answer 10

• Colorectal carcinoma
• Diverticular stricture
• Hernia
• Volvulus
• Pseudo-obstruction

Question 11

What is a volvulus?

Answer 11

A volvulus is when the colon twists around mesentery

Question 12

In 3 steps, describe how a volvulus occurs

Answer 12

⇒ Enclosed bowel loop

⇒ Dilates

⇒ Perforation / ischaemia

Question 13

What is the most common volvulus and how does it occur?

Answer 13

Sigmoid volvulus:

• Starts in LIF
• Coffee bean sign towards RUQ
• Dilatation of proximal bowel

Question 14

AXR is not the gold standard for infection and inflammation. However, one might see acute or chronic changes.

Identify some

Answer 14

• Mucosal thickening
• Featureless colon
• Bowel wall oedema

Question 15

Which soft tissue structures can be seen in an AXR?

Answer 15

• Organs
• Musculature

Question 16

Specifically, identify some organs which can be observed in an AXR

Answer 16

• Liver
• Spleen
• Kidneys
• Bladder
• Lung bases

Question 17

Identify some bones which can be seen in an AXR

Answer 17

• Pelvis
• Sacrum
• Coccyx
• Lumbar spine
• Lower thoracic spine
• Lower ribs

Question 18

Identify 5 other abnormalities which can be observed in an AXR

Answer 18

• Stones
• Organs/masses
• Calcification (pancreatitis, vascular, nodes)
• Artefact
• Foreign body

Question 19

Describe the use of an erect chest X ray

Answer 19

• Erect CXR is a specific examination performed for the assessment of subdiaphragmatic free gas (pneumoperitoneum)
• It is used to assess patients with acute abdominal pain

Question 20

Perforation leads to pneumoperitoneum.

Identiy 6 possible causes of this

Answer 20

• Peptic ulcer
• Diverticular
• Tumour
• Obstruction
• Trauma
• Iatrogenic (laparoscopy)

Question 21

What is the purpose of contrast studies?

Answer 21

Contrast is used to define hollow viscera (Barium, water soluble)

Question 22

Identify 4 common GI contrast studies

Answer 22

• Swallow
• Meal
• Small bowel enema/follow through
• Enema

Question 23

Identify the visible abdominal structures in the cross-sectional abdominal CT at T12 below:

Answer 23

Question 24

Identify the visible abdominal structures in the cross-sectional abdominal CT at L1 below:

Answer 24

Question 25

Identify the visible abdominal structures in the cross-sectional abdominal CT at L3 below:

Answer 25

Question 26

Identify the visible abdominal structures in the cross-sectional abdominal CT at L4 below:

Answer 26