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Gastrointestinal > Lecture 19– imaging of the GI tract > Flashcards

Lecture 19– imaging of the GI tract Flashcards

1
Q

Imaging available for GI system

A
  • Plain X-rays
    • Abdominal x-ray (AXR)
    • Erect chest x-ray (CXR)
  • Contrast studies
    • Barium swallow/enema
    • Barium meal/follow through
    • Water soluble contrast studies
  • US
  • Cross- sectional imaging
    • Computed tomography
    • Magnetic resonance imaging (MRI)
  • Angiography
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2
Q

AXR is …….. utilised as a first line investigation

A

less

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3
Q

when is AXR used vs CT scan in relation to small or large bowel obstruction

A
  • CT scan is first for small bowel obstruction
  • Abdo x-ray may show volvulus in large bowel obstruction
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4
Q

first line investigation for renal colic

A

CT

  • abdo Xray can be done to check stone ahs passed
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5
Q

AXR and Acute exacerbation of IBD?

A

Potentially useful for toxic megacolon with perforation

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6
Q

presentation of small bowel obstriction on X-ray

A
  • Central position
  • Often don’t see (need gas in the bowel to see)
  • Plica/circulares/ permanent folds/ Valvulae conniventes
    • Cross the entire wall
    • Thin
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7
Q

which rule applies for large boewl obstruction

A

369

The 3-6-9 rule is a simple aide-memoire describing the normal bowel calibre:

small bowel: <3 cm

large bowel: <6 cm

appendix: <6 mm
caecum: <9 cm

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8
Q

presentation of large bpewl obstruction

A
  • Peripheral position
  • Haustra- sacculation’s formed by outer longitudinal muscles
    • Lines only extend partially along the bowel wall
  • Remember
    • Transverse colon hands down to the pelvic
    • Sigmoid colon can loop and be long

example cause: diverticular stricture

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9
Q

Ct and small bowel obstruction

A
  • CT = first line of imaging
  • Can identify the level and cause of obstruction
  • Also good helping to determine whether bowel is strangulated
  • Do not use plain abdominal radiographs unless CT unavailable
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10
Q

why is CT most widley used method in large bowel obstruction

A
  • Localise location of obstruction but in most instances also identify causes
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11
Q

sigmoidal volvulus is said to look like a

A

coffee bean

  • Due to a twist at the base of the sigmoid mesentery which is in a fixed position (*) in the left iliac fossa
  • This results in the appearance of a giant coffee bean, the typical sign of sigmoid volvulus
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12
Q

toxic megacolon can be caused by

A
  • Acute deterioration with UC or colitis
  • patient will be unwell
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13
Q

Toxic megacolon- X-ray

A
  • Colonic dilatation
  • Oedema
  • Pseudopolyps
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14
Q

erect CXr will be in

A

AP

  • cant get accurate reading o heart side
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15
Q

what may you need an erect chest X-ray for inr regards to the GI system

A

Pneumoperitoneum

  • An erect chest x-ray can show even a very small volume of abdominal gas
  • Reference to the clinical setting is required to determine if this a life threating perforation
  • A careful check should be made for free gas under the diaphragm on every chest X-ray
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16
Q

iatrogenic causes of penumoperitoneum

A
  • Patient might have undergone laparoscopic surgery earlier in the day free gas under diaphragm is insufflated CO2- an acceptable post surgery finding
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17
Q
  • Causes of pneumoperitoneum
A

perforation due to

  • Peptic ulcer
  • Diverticular
  • Tumour
  • Obstruction
  • Trauma
  • Iatrogenic
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18
Q
A
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19
Q

x-rays are also useful in looking for

A
  • stones and calcificatione e.g. in chronic pancreatitis
  • foregein bodies
20
Q

barium swallow is a dedicated test of the

A

pharynx, oesophagus and proximal stomach

  • You give pt barium to swallow then use video fluoroscopy (which is a continuous X-ray which is view in Realtime on a screen)
21
Q

what has largely replaced barium swallow for the assessemnt of peptic ulcer disease and elevation haematemesis

A

Upper GI endoscopy has largely replaced barium swallow for the assessment of peptic ulcer disease and elevation of haematemesis

22
Q

Barium follow-through

A
  • Following a barium swallow, we can wait for the barium to reach the small intestine
  • Therefore can be used to image small intestine (endoscopy cannot reach here)
23
Q

barium enema

A
  • Tube inserted into rectum
  • Administered and results monitored by fluoroscopy
  • If mucosal problems are suspected then adding another contrast medium (air or CO2) will help
  • Largely superseded by CT
  • Used to visualise:
    • Strictures
    • Mucosal problems (with air or CO2)

CT shows UC

24
Q

abdominal ultrasound uses

A
  • Use of sound waves to generate image
    • Frequency above audible range of human hearing (20 KHz)
    • Usually 2-18 MHz)
25
Q

pros and cons of abdominal ultrasound

A
  • Pros
    • Cheap compared to CT and MRI
    • Portable
  • Cons
    • Highly user dependent
26
Q

CT scan show different features at

A

various spinal levels

27
Q

lets orientate ourselves- The CT is as if we are standing

A

As if we were standing at the persons feet

  • On the right
    • The liver
28
Q

CT-T12 will visualise the

A
  • Aortic hiatus of the diaphragm
    • When celiac drunk is given off
29
Q

CT L1 (transpyloric plane) will visualise the

A

L1- Midgut

  • Also known as transpyloric plane
    • Fundus of the gallbladder
    • Pylorus of stomach
    • Neck of pancreas
    • Superior mesenteric artery origin
    • Hilum of kidneys
      • Left: above
      • Right : below
  • Dark area on the stomach= gas  can see fluid level of the stomach
30
Q

CT L3 will visualise the

A

L3- Hindgut

  • Umbilicus
  • Bottom of liver
  • Can see more SI
  • Inferior mesenteric artery
31
Q

CT L4

A

L4

  • Iliac crest
  • Bifurcation of abdominal aorta
32
Q

MRI pros and cons

A
  • Pros
    • No radiation (magnetic fields)
    • Soft tissues, tendons and the brain
  • Cons
    • Not applicable for those with metal implants
    • Very claustrophobic
    • Takes longer
33
Q

what are MRI vs CT scan used to visualise

A

MRI- looking at soft itsuse,s tnedons, ligaments, spinal cords and the brain

CT- imaging injuries from truama, staging cancer and diagnosing conditions of blood vessels

34
Q

bony sturctures more or less clear in MRI than CT

A

less clear

35
Q

MRi powered by

A

storng magentic filed

CT powered by low dose radiation

36
Q

what takes longer MRI or CT

A

MRI (30 mins) vs 5-10min CT

37
Q

what must we beware of with MRI scan

A

pts with metal or certain emdical impalnts cannot undergo MRI due to magentic field pulses

38
Q

Abdominal MRI anatomy

A
39
Q

GI angiography

A
  • A ways of visualising the vasculature associated the intestines
  • CT angiography has replaced conventional angiography for mesenteric vasculature
  • Can get a 3D reconstruction
40
Q

celiac trunk found at

A

T12

41
Q

celeiac drunk splits into

A
  • Left- splenic artery and left gastric
  • Right – common hepatic artery
42
Q
  • Superior mesenteric artery at
A
  • L1
    • Branches
43
Q

branches of superior mesenteric

A
  • middle colic
  • right colic
  • illeocolic
  • illeo and jejunal branches
44
Q
  • Inferior mesenteric artery at
A
  • L3
    • Goes off slightly to the left and drops into the pelvis without branching –> superior rectal artery
45
Q

branches of the infeiror emsenteric

A

left colic

sigmoid

superior rectal

Gastrointestinal (35 decks)

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