Abdominal X-rays Flashcards
What are the indications for AXR? (x4 +1)
Gases (obstruction, ileus, ischaemic colitis, pneumoperitoneum), masses (including AAA), bones, stones. Plus acute flare of IBD to confirm/exclude megacolon.
How do you interpret AXR?
- PATIENT DETAILS
- Date and time of AXR
- FILM – AP or PA
- Rotation, penetration, exposure (RIPE without the ‘I’)
- B – Bowel and organs: biliary tree, urinary tract, bowel, small intestine, liver, kidneys, bladder. Present as ‘normal gas pattern’ and ‘no abnormalities can be discerned from other abdominal viscera’
- B – Bones
- C – Calcification and artefacts
- Document
What are the sizes of small bowel, large bowel and caecum?
3-6-9 rule: Small bowel over 3cm; large bowel over 6cm; caecum over 9cm
How do you differentiate between small bowel and large bowel in AXR? (x3)
- Width
- Small bowel has valvulae conniventes (full width of bowel, more regular and finer than haustra); large bowel has haustra and semi-lunar folds (plicae semilunaris – lie between haustra and don’t go across whole lumen). NB: semi-lunar folds are the LINES, and haustra and SACS
- Small bowel grey as contains air and fluid. Large intestine is blacker as contains gas
How are supine and erect x-rays used to assess gas pattern?
Supine best for bowel gas pattern; erect CXR best for perforation.
What are the signs of obstruction in obstruction on AXR?
Dilated small intestine and/or dilated large intestine
What are the causes of large bowel obstruction? (x3)
Malignancy, diverticulitis, volvulus.
What is toxic megacolon?
AKA toxic dilatation. Complication of IBD, usually UC, and involves inflammation and damage to bowel wall.
What does toxic megacolon look like on AXR? (x4)
Large intestine dilatation, colon wall thickening and loss of mucosal folds. May see perforation.
What is coffee bean sign?
Grossly dilated segments of bowel seen in sigmoid and caecal valvulae. Can be HUGE, so don’t get confused.
How do you differentiate between a sigmoid and caecal volvulus on AXR?
Sigmoid loop typically points to RUQ from LIF. Caecal from RLQ to LUQ
How may signs of obstruction differ between competent and incompetent caecal valve?
Competent valve: peristalsis continues to push faeces in the bowel, with no possibility for retrograde flow. As such, patients are more likely to develop volvulus with subsequent perforation. Patients with incompetent valves can permit retrograde faecal flow, so don’t have faecal loading in the colon, but are instead more likely to present with faecal vomiting.
What are the signs of inflammatory colitis on AXR?
Loss of mucosal folds, thumbprinting, and bowel wall thickening.
What is thumb-printing? What causes this? (x2)
Protrusion of thickened mural folds into the lumen, seen in large bowel ischaemia and colitis.
What are the causes of extraluminal air in the abdomen? (x4)
- Pneumoperitoneum
- Gas in urinary tract, for example in the bladder from fistula
- Gas in biliary tree, called pneumobilia
- Intramural gas (in bowel walls) from bowel necrosis
What is mottling on AXR? When is this normal or abnormal?
Indicates presence of trapped gas within faeces and is a normal sign in the ascending colon. In the descending colon, it is abnormal and would indicate constipation.
What is the lead pipe sign?
Loss of normal haustral markings secondary to UC.
What is this? What could you infer if this wasn’t present?
Gas in the rectum. This is normal. If absent, it could be a sign of obstruction.
What does diverticulitis look like on AXR?
Visualise out-pouchings in barium enema
What is staghorn calculus?
Form a cast of the renal pelvis and at least two calyces.
