Abdominal X-ray and CT

DIAGNOSES

Bowel obstruction

• work out whether small or large bowel.
• work out transition point between dilated and collapsed bowel (start at rectum and work backwards).

Sigmoid volvulus

• coffee bean sign = distended segment of large bowel folded back on itself so that the twisted loops causes two compartments with a central double wall ending in the apex of the twist

Caecal volvulus

• large bowel dilation in pelvis but not coffee bean in appearance
• sigmoid and rectum normal on CT
• “whirl sign” – direct visualisation of the twisted segment of bowel

Bowel perforation in ICU

• difficult to get erect CXR
• perform a left lateral AXR -> can see free air under diaphragm and above liver
• gas on x-ray may persist for 7/7 post laparotomy
• supine AXR:

-> Rigler sign: both inner and outer borders of bowel well defined
-> football sign: air outlines the entire peritoneal cavity with a football shape
-> interloop triangular lucency: triangle of gas between two loops of bowel and abdominal wall
-> subhepatic air: RUQ outlines the inferior border of liver
-> falciform ligament outlined by air: vertical soft tissue density between umbilicus and notch between left and right lobes of liver

Renal injury assessment

• requires an early phase to assess vascular sufficiency/parenchyma and late phase to assess for extravasation of urine.

Pneumatosis intestinalis

• primary (idiopathic or benign)
• secondary (bowel necrosis, bowel obstruction, IBD, immunosuppression, trauma)

Pancreatitis

• area involved (head, body, tail)
• enhancement -> degree of necrosis
• fat stranding
• look for cause: gall stones (not often seen) or dilated CBD
• look for complications: fluid collections, pseudocyst, abscess, pseudoaneurysm, haemorrhage

Pelvic Fractures

1. anteroposterior compression (external rotation of the hemipelvis)
2. lateral compression (internal rotation of hemipelvis)
3. vertical shear
4. complex (a combination of multiple patterns of force)

• if there is more than 2.5cm of pubic rami diastasis there must be additional injury to the posterior ligaments.

TIPS AND TRAPS

• small bowel: more central, plicae circulares (circumferential)
• large bowel: more peripheral, haustra (not circumferential)
• if bowel obstruction seen look for: free air, pneumatosis intestinalis and/or gas in portal vein
• if caecum exceeds 12 cm in diameter -> high risk of perforation and decompression should be considered
• if small bowel > 3cm = distended
• placing the film on lung windows can demonstrate subtle evidence of intra-abdominal free gas

References and Links

LITFL

• Hartung MP. Abdominal CT interpretation course. LITFL
• CCC – AXR Interpretation
• Eponymictionary – Leo George Rigler (1896 – 1979) and Rigler sign (1941)
• Top 10 X-Ray foreign bodies

Journal articles

• James. The Abdominal Radiograph. Ulster Med J 2013;82(3):179-187