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Gastro-intestinal System > Abdominal Radiography > Flashcards

Abdominal Radiography Flashcards

0
Q

What are some of the risks of radiation exposure?

A

Carcinogenesis

Genetic

Developmental risk to foetus

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1
Q

Compare the radiation doses of different types of investigations.

A

ULTRASOUND - no radiation (cheap, portable, highly user-dependent)

MRI - no radiation, but any metal in body will heat (good spatial/contrast resolution, time-consuming)

AXR - 1mSv (CXR = ~0.04mSv) - more tissue to penetrate than CXR

BARIUM ENEMA - 7mSv

CT abdo/pelvis - 15mSv

note: background radiation in UK = ~1-3mSv

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2
Q

Give some examples of scenarios where an AXR will be performed.

A

Small/large bowel obstruction suspected

Acute exacerbation of IBD (in case of toxic megacolon)

Acute abdominal pain
note: although usually the suspected cause does not require an AXR to diagnose

note: CT used for suspected renal calculi (not all show up on X-ray)

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3
Q

What are the features seen on AXR?

A

note: AP
- bowel gas pattern = normally not present in small intestine (rapid peristalsis) but present in colon (slow transit + faeces + gas) and stomach
note: hollow tubes completely filled with fluid should NOT be visible
- soft tissue structures e.g. liver, spleen, kidneys, bladder, lung bases, musculature (psoas major shadow)
- bones e.g. pelvis, sacrum, coccyx, lumbar spine, lower thoracic spine, lower ribs

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4
Q

What approach should be used when reading an AXR?

A

A = air/gas

B = bowel

C = calcification (bones & stones)

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5
Q

How can the small intestine be identified on an AXR?

A

Central position

Valvulae conniventes/circular folds/valves of Kerckring/plicae circulares (reduplications of mucous membrane projecting into the lumen of the small intestine)

  • cross entire wall and remain thin ( >3cm normal - check against vertebral height ~ 3cm)
  • permanent (not obliterated when intestine is distended)
  • reach around entire circumference of intestine
    note: usually should NOT be able to see bowel gas pattern due to rapid peristalsis
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6
Q

How can the large intestine be identified on an AXR?

A

Peripheral position (frames small bowel loops)

Transverse colon hangs down to pelvis (larger in females; therefore sometimes appears in pelvic X-ray)

Sigmoid colon can loop and be very long

Haustra

  • do not reach around entire circumference of intestine
  • transverse colon should be < 6cm
  • caecum should be < 9cm

Bowel gas pattern should be visible due to slow transit + presence of faeces/gas

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7
Q

What are some causes of an abnormal bowel pattern on an AXR?

A
  • small bowel obstruction (3cm 6cm, caecum > 9cm)

note: check competence of ileocaecal valve
- incompetent = dilated small bowel
- competent = stops backflow of faeces -> gas builds up -> perforation

  • ileus (intestinal obstruction, usually of ileum)
  • volvulus (twisting of a part of the digestive tract -> ischaemia/perforation)
    note: sigmoid colon common due to length/flexibility; caecum uncommon (unless anatomical defect present)
  • toxic megacolon
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8
Q

What is toxic megacolon?

A

Acute form of colonic distension (usually a complication of IBD)

Characterised by:

  • very dilated colon
  • abdominal distension
  • fever/abdominal pain (shock)
  • sometimes oedema & pseudopolyps
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9
Q

Give some examples of causes of small intestinal obstruction.

A

EXTRINSIC:
Adhesional (due to previous surgery) - most common
Hernias - second most common
Volvulus

BOWEL WALL LESIONS:
Tumours
Crohn’s disease

INTRA-LUMINAL: 
Foreign bodies 
Food bolus (rare)
Meconium (cystic fibrosis)
Gallstones 
Intussusception
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10
Q

How does small intestinal obstruction present?

A
  • vomiting (early)
  • distension (mild)
  • absolute constipation (late)
  • colicky pain
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11
Q

Define absolute constipation.

A

No faeces or flatus passed

note: if due to an obstruction, faeces past point of obstruction can be egested

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12
Q

What are the qualities of colicky pain?

A

Pain which comes and goes

note: true colic has a baseline of no pain (GI obstruction)

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13
Q

Give some examples of causes of large intestinal obstruction.

A

Colorectal carcinoma - ~60%

Diverticular stricture - ~20%

Hernias - ~5%

Volvulus

Pseudo-obstruction (disorder of nerves/muscles affecting movement of food/flatus through large intestine mimicking obstruction)

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14
Q

How does large intestinal obstruction present?

A
  • vomiting (late, faeculant)
  • significant distension
  • pain
  • absolute constipation
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15
Q

How can an AXR detect signs of inflammation or infection?

A
  • mucosal thickening of bowel
  • featureless colon (“lead pipe” colon)
  • bowel wall oedema (“thumb printing”)
16
Q

How does volvulus present?

A

Pain starts in LIF (sigmoid volvulus)

Distension of proximal bowel

“coffee bean” sign in RUQ on AXR

17
Q

Give some examples of abnormalities seen on AXR other than obstruction.

A

Calculi

Organs/masses

Calcification (pancreatitis, vascular, nodes)

Bone abnormalities

Artefacts e.g. naso-jejunal tube

Foreign body e.g. naso-gastric tube in bronchus

note: perforation better seen on CXR (see pneumoperitoneum under diaphragm) or on transverse/axial CT (better spatial resolution)

18
Q

Give some examples of causes of perforation.

A

Peptic ulcer

Diverticula

Tumour

Obstruction

Trauma

Iatrogenic e.g. laparoscopy

19
Q

What contrast studies can be used for imaging of the GI tract?

A

Used to define hollow viscera (and test for mobility; less good on pathology)

Use barium or water-soluble mixture (if worried about risk of aspiration/perforation)

  • barium swallow: detect aspiration/dysphagia mechanism
  • barium meal
  • barium follow-through
  • barium enema (show diverticula & polyps)
20
Q

What structures can be seen on an axial CT at L1?

A

(trans-pyloric plane)

note: axial means transverse

  • bile duct
  • splenic hilum
  • renal hilum
  • pylorus of stomach
  • neck of pancreas
21
Q

How should suspected bowel obstruction be initially managed?

A

(before cause is known)

Nil by mouth
Nasogastric tube
IV fluids
Antibiotics (Gram-ve anaerobes)

22
Q

What is an ERCP? When may it be performed? What are the risks of this procedure?

A

Endoscopic retrograde cholangiopancretography

Endoscope introduces contrast into biliary tree and pancreatic ducts

note: can also enlarge the sphincter of Oddi and potentially remove gallstones trapped in the common bile duct
e. g. pancreatic cancer

Risks (5%-10%)

  • cholangitis
  • perforation of biliary tree
  • pancreatitis
  • haemorrhage

Gastro-intestinal System (16 decks)

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