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GI Unit > 10.1 GI Imaging > Flashcards

10.1 GI Imaging Flashcards

1
Q

What x-rays are used to image he GI tract?

A

Abdominal x-ray AXR

Erect chest x-ray CXR

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2
Q

What contrast studies might be used to view the GI system?

A

Barium swallow and video fluoroscopy - upper GI tract
Barium enema - distal GI tract
Barium meal/follow through - small intestines
Water soluble contrast studies

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3
Q

What are the 5 modes of imaging the GI system?

A 
Plain x-rays
Contrast studies
Ultrasounds
Cross-sectional imaging (MRI/CT)
Angiography
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4
Q

What are the 3 spinal levels we take CT scans of the GI tract at?

A

T12
L1
L3

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5
Q

Why request an AXR?

A

Acute abdominal pain

  • useful for large bowel obstruction as volvulus show up clearly on abdo X-ray
  • not useful for small bowel obstruction

Acute exacerbation of IBD - if suspecting toxic megacolon with perforation

Renal colic - CT first line but abdo xray can be done before surgery to see if stone has passed

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6
Q

How does small bowel obstruction present on a plain abdominal x-ray?

A

Central position
Often dont see without contrast of gas/air
Plicae circulares on wall - tine lines that cross entire wall

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7
Q

How does an obstructed large bowel appear oN a plain ABX?

A

Peripheral position - may appear sentrally as the transverse colon can hang down and sigmoid colon can loop and be long
Haustra - lines only extend partially

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8
Q

What are haustra?

A

Saculations of the large bowel due to the contraction of out longitudinal muscle

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9
Q

What is the first line treatment for small bowel obstruction?

A

CT scan

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10
Q

Why is CT scan useful to image small bowel obstruction?

A

Can identify level and cause of the obstruction

Can determine if bowel in strangulated

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11
Q

Why is CT the first line for imaging large bowel obstruction?

A

Confirm diagnosis
Localise the location of obstruction
Identify the cause

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12
Q

Why might an ABX of the large bowel be useful?

A

Colonic distension - gaseous secondary to gaseous producing organisms in faeces
Small bowel dilation in incompetence of ileocaecal valve
As LI sits peripherally we may be able to determine level of obstruction due to surrounding features

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13
Q

How wide can a large bowel distend?

A

6cm

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14
Q

What is the 3 6 9 rule?

A

The widths regions of bowel can be distended to during obstruction
3cm = small bowel
6cm = large bowel
9cm = caecum

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15
Q

What is a sigmoid volvulus?

A

Twist at the base of the sigmoid mesentery in the left iliac fossa.

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16
Q

Why is the sigmoid bowel prone to volvulus?

A

As the sigmoid bowel has its own mesentery. The descending bowel is retroperitoneal and has no mesentery

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17
Q

What is the sigmoid prone to twisting?

A

Constipation - full of faeces

Sigmoid tumour

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18
Q

How does a sigmoid volvulus appear on an xray?

A

Large dilated coffee bean appearance

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19
Q

What is toxic megacolon?

A

Colonic dilatation due to acute deterioration with UC or colitis. Oedema and pseudopolyps.

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20
Q

How does toxic megacolon appear on an xray?

A

Very dilated large bowel.

Mucosal islands - fluffy lighter patches in the swollen bowel

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21
Q

What is an erect CXR most useful for imaging in the GI tract?

A

Perforation resulting in pneumoperitoneum

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22
Q

What is pneumoperitoneum?

A

When air/gas has entered the peritoneal cavity

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23
Q

How is a pneumoperitoneum imaged?

A

Erect CXR

Dark regions under the diaphragm shows presence of gas in the peritoneal cavity

24
Q

What might cause perforation of the GI tract?

A
  • Peptic ulcer
  • Diverticular
  • Tumours within GI tract
  • Obstruction
  • Trauma
  • Iatrogenic
25
Q

When might gas under the diaphragm in a CXR be an acceptable finding?

A

Post laparoscopic surgery

Patients are Insufflated with carbon dioxide to expand the visible field for surgeons.

26
Q

What direction are CXR looking for bowel perforation taken in?

A

AP direction

27
Q

What unintentional findings might appear on a ABX?

A

Stones and calcification (e.g. chronic pancreatitis)

Foreign bodies

28
Q

What structures can be imaged with a barium swallow?

A

Pharynx
Oesophagus
Proximal stomach

29
Q

What is a barium swallow?

A

Patient swallows barium

Videofluoroscopy to observe the path of the barium

30
Q

What imaging technique is used to visualise peptic ulcer disease and evaluate haematemesis?

A

Upper GI endoscopy

31
Q

What is a barium follow through?

A

Barium ingested by patient. Wait for barium to travel down to the small intestine before imaging

32
Q

What is a barium enema?

A

A tube inserted into the rectum and barium is infused.
Results monitored using fluoroscopy
Can add in another contrast medium (air/CO2) to shoe mucosal problems

33
Q

What is a barium enema used for?

A

To image the colon

34
Q

What are the advantages of using abdominal ultrasound?

A

Uses sound waves to generate images (not ionising)
Cheap compared to CT and MRI
Portable
Fast scanning

35
Q

What are the disadvantages of abdominal ultrasound?

A

Highly user dependent - few people are competent

36
Q

What can an ultrasound scan of the abdomen be used for?

A

Imaging gallbladder and gallstones

Stones in bile duct

37
Q

What structures are seen on a CT scan at spinal level T12?

A

Aortic hiatus of the diaphragm

Coeliac artery

38
Q

What structures are seen on a CT scan at spinal level L1?

A 
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)
Superior mesenteric artery
39
Q

What structures are seen on a CT scan at spinal level L3?

A

Umbilicus

Inferior mesenteric artery

40
Q

What structures are seen on a CT scan at spinal level L4?

A

iliac crest

bifurcation of abdominal aorta

41
Q

What structures are useful for orientation in a CT scan?

A

RHS = liver
Stomach lies anterior and to RHS of liver
Vena cava lies on posterior border of stomach
Spleen lies posterior to stomach

42
Q

Why might the right kidney not be seen on a CT scan of T12?

A

As liver on RHS and displaces right kidney down. Left kidney visible at T12

43
Q

What structures are visible in a CT of L1 that weren’t visible at T12?

A 
Pancreas
Superficial mesenteric artery
Right kidney 
Portal vein 
Small intestine (very variable)
44
Q

What structures become visibile at L3 that weren’t at L1?

A

IVC is separated from the liver
A lot more small intestine (ileum/duodenum)
Colon anteriorly
Psoas muscles

45
Q

what are MRI used to image?

A 
Soft tissues
Tendons
Ligaments
Spinal cords
Brain
46
Q

What are the advantages of MRI?

A

No ionisation

Good soft tissue imaging

47
Q

What are the disadvantages of MRI scan?

A

Bony structures less detailed than CT
Claustrophobia/anxiety as taken in large tube
Long duration (30 mins)
Loud noises
May be asked to hold breath - difficult for some patients
Unsuitable for patients with metal or certain medical implants

48
Q

What are the advantages of a CT scan?

A

Good for imaging trauma, staging cancer, diagnosing conditions in blood vessels
Bony structures and clearer and more detailed
Machine more comfortable than MRI - not fully enclosed
Shorter duration of time than MRI (5-10mins)
Holding breath not required as much
Can be performed with no risks to medical implants or metal

49
Q

What are the disadvantages of CT scans?

A

Use ionising radiation

Soft whirring noises and flashing lights may be unsettling ( less so than MRI )

50
Q

What is GI angiography used for?

A

A way of visualising the vasculature associated with the intestines

51
Q

Why has CT angiography replaced conventional angiography for mesenteric vasculature?

A

As can get a 3D reconstruction from CT scan to get better idea of what’s going on.

52
Q

Describe the path of the abdominal aorta from the thorax into the abdomen

A

Initially on the left hand side, travels inferiorly by moving to a more anterior and central position

53
Q

What pathology can result in an enlarged aortic artery in a CT angiogram?

A

Abdominal aortic aneurism

54
Q

Where does the abdominal aorta bifurcate?

A

At L4 into the common iliac vessels

55
Q

Where does the IVC sit in relation to the abdominal aorta?

A

To the RHS

56
Q

How does the gallbladder present on a CT scan?

A

A darker circular structure directly beneath the liver on the RHS

57
Q

What are the 3 branches of the coeliac trunk?

A

Hepatic artery
Splenic artery
Left gastric artery

GI Unit (14 decks)

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