What are the 5 different imaging modalities of the GI tract?
- Plain X-rays – AXR, CXR
- Contrast studies – Barium swallow, enema, meal/follow through, water soluble contrast studies
- Cross-sectional imaging – CT, MRI
Why request an abdominal X-ray?
- Acute abdominal pain
- Small/large bowel obstruction
- Acute exacerbation of IBD
- Renal colic
What are the features of an AXR?
- Calcification (bone and stones)
In terms of bowel gas patterns, what kind of structures are visible in an AXR?
- Visible if gas filled / gas and fluid filled
- Not visible is fully fluid filled
The bowel gas patterns in an AXR varies according to transit time.
- Slow transit = colon (faeces ± gas)
- Medium transit = stomach (fluid + lots of gas)
- Fast transit = small bowel (fluid)
Identify 5 conditions which produce abnormal bowel gas patterns in an AXR
- Small bowel obstruction (>3 cm)
- Large bowel obstruction (>6 cm)
- Paralytic Ileus
- Toxic Megacolon
How does small bowel obstruction present?
- Vomiting (early)
- Distension (mild)
- Absolute constipation (late)
- Colicky pain
What are the causes of small bowel obstruction?
- Hernias (inguinal, femoral, incisional)
How does large bowel obstruction present?
- Vomiting (late, faeculant)
- Distension (significant)
- Absolute constipation
What are the causes of large bowel obstruction?
- Colorectal carcinoma
- Diverticular stricture
What is a volvulus?
A volvulus is when the colon twists around mesentery
In 3 steps, describe how a volvulus occurs
⇒ Enclosed bowel loop
⇒ Perforation / ischaemia
What is the most common volvulus and how does it occur?
- Starts in LIF
- Coffee bean sign towards RUQ
- Dilatation of proximal bowel
AXR is not the gold standard for infection and inflammation. However, one might see acute or chronic changes.
- Mucosal thickening
- Featureless colon
- Bowel wall oedema
Which soft tissue structures can be seen in an AXR?
Specifically, identify some organs which can be observed in an AXR
- Lung bases
Identify some bones which can be seen in an AXR
- Lumbar spine
- Lower thoracic spine
- Lower ribs
Identify 5 other abnormalities which can be observed in an AXR
- Calcification (pancreatitis, vascular, nodes)
- Foreign body
Describe the use of an erect chest X ray
- 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
Perforation leads to pneumoperitoneum.
Identiy 6 possible causes of this
- Peptic ulcer
- Iatrogenic (laparoscopy)
What is the purpose of contrast studies?
Contrast is used to define hollow viscera (Barium, water soluble)
Identify 4 common GI contrast studies
- Small bowel enema/follow through
Identify the visible abdominal structures in the cross-sectional abdominal CT at T12 below:
Identify the visible abdominal structures in the cross-sectional abdominal CT at L1 below:
Identify the visible abdominal structures in the cross-sectional abdominal CT at L3 below:
Identify the visible abdominal structures in the cross-sectional abdominal CT at L4 below: