Lecture 8.1: Imaging of the Gastrointestinal Tract Flashcards
Imaging Modalities of the GIT (6)
- Plain X-Ray
- Contrast X-Ray (barium meal/enema)
- CT scan
- Angiography
- MRI
- Ultrasound
What Information is on an Imaging Request Form (11)
1) Where is the request being carried out?
2) Patient demographics
3) How mobile is the patient?
4) Any allergies?
5) Referrers details and signature
6) Referrers contact details (e.g. bleep number)
7) Clinical details
8) Previous studies available?
9) Investigation requested
10) Location of patient
11) Consultant responsible for care
Indications for AXR (4)
- Gases
- Masses
- Bone
- Stones
X-Ray Basics: Black
Air/Gas
X-Ray Basics: Dark Grey
Fat
X-Ray Basics: Light Grey (2)
- Soft Tissue
- Fluid
X-Ray Basics: White
Bone and Calcified Structures
X-Ray Basics: Bright White
Metal
Assess Image Type and Quality (3)
- Projection of image (AP or PA)
- Exposure of image
- Orientation
Interpretation Structures: BBC
- Bowel and Other Organs (Gases and Masses)
- Bones
- Calcification and Artefacts (Stones)
Interpretation Structures: ACPOP
- Air (gases)
- Calcification (stones)
- Psoas (masses)
- Organomegaly and Soft Tissue (masses)
- Pelvis and Spine (bones)
How does the Small Bowel appear on an AXR?
- Usually lies more centrally
- Don’t often see
- Mucosal folds (valvulae conniventes) visible across full
width of bowel - “Coiled spring appearance”
- Upper limits of normal diameter 3cm
How does the Large Bowel appear on an AXR?
- Around the side of abdomen
- Colon 6cm diameter
- Caecum 9cm diameter
What are Haustra?
- Pouches/sacculations that protrude into the lumen
- Separate by plicae semilunaris
- Thicker than valvular conniventes
- Do not transverse the whole bowe
What sizes are bowel obstructions?
- Small bowel obstruction >3cm
- Large bowel obstruction >6cm
- Caecum >9cm
What is Volvulus?
Occurs when a loop of intestine twists around itself and the mesentery that supplies it, causing a bowel obstruction
Why is Volvulus a Surgical Emergency? (2)
- Risk of Perforation
- Risk of Ischaemia
What does Volvulus look like on AXR?
The twisted loop of sigmoid colon is said to resemble a coffee bean
What is a Toxic Megacolon?
A rare, but potentially deadly complication of colonic inflammation
What does a Toxic Megacolon look like on an AXR?
Dilated transverse colon (>6cm)
What is the most common cause of Small Bowel Obstruction?
- Adhesions most common cause (75%)
- Abdominal hernia (10%)*
- Neoplastic masses (intrinsic or extrinsic compression)
How does a Small Bowel Obstruction present?
- Vomiting (early)
- Abdominal distension
- Absolute constipation (late)
- Colicky pain
What are some common of cause Large Bowel Obstructions?
- Colorectal carcinoma
- Diverticular strictures
What are some less common of cause Large Bowel Obstructions?
- Hernias
- Volvulus
- Pseudo-obstruction
How does a Large Bowel Obstruction present?
- Vomiting (late, feculent)
- Distension (significant)
- Pain
- Absolute constipation
Sigmoid Volvulus vs Caecal Volvulus
In a cecal volvulus, the base of the distended bowel loop arises from the right lateral abdomen or right lower quadrant (points to LUQ)
Sigmoid volvulus where it arises from the pelvis (points to RUQ)
Radiological Features of IBD
- Yellow arrow = lead pipe sign of the distal transverse
colon (loss of normal haustra markings) - Red arrow = thumb printing of the proximal transverse
colon (mucosal thickening of haustra)
What Organs can be seen on an AXR? (8)
- Lungs
- Liver
- Gallbladder
- Stomach
- Psoas Muscles
- Kidneys
- Spleen
- Bladder
What Bones can be seen on an AXR? (6)
- Ribs
- Lumbar Vertebra
- Sacrum
- Coccyx
- Pelvis
- Proximal Femurs
What Calcifications are seen on an AXR? (5)
- Calcified gallstones
- Renal stones/staghorn calculi
- Pancreatic calcification
- Vascular calcification
- Costochondral calcification
What is Rigler’s Sign?
An indication of free air enclosed within the peritoneal cavity (pneumoperitoneum), imprinting a visible pattern on a plain radiographic image of the abdomen, in supine technique
Magnetic Resonance Cholangiopancreatigram (MRCP)
It is a special type of magnetic resonance imaging (MRI) exam that produces detailed images of the hepatobiliary and pancreatic systems, including the liver, gallbladder, bile ducts, pancreas and pancreatic duct.
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