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CT abdomen

Interpretation of the CT abdomen scan

basic concepts

  • nearly all urologic calculi are radio-opaque on CT scan except for rare drug calculi (ciprofloxacin, indinavir, sulphonamides)
    • differentiate ureteric calculi from phleboliths by evidence of surrounding inflammation around the ureteric calculus
  • look for “dirty fat” (denser than normal fat) as evidence of localised inflammation
  • hollow organs are just mucosal lining in a muscular tube - wall thickness and enhancement pattern are key to the diagnosis
    • in suspected bowel obstruction look for:
      • faeces sign as the location of obstruction
      • evidence of perforation, abscess, fistula, ischaemia
        • free fluid, mesenteric congestion, and absent mucosal enhancement are all signs of ischaemic gut
    • caecal volvulus
      • extreme dilatation of the cecum (with haustral creases in the upper left quadrant)
      • fetal shape, faeces evident in descending colon on left abdomen
      • whirl sign
      • X-marks-the-spot sign,
    • sigmoid volvulus
      • large gas-filled loop without haustral markings, forming a closed-loop obstruction
      • whirl sign: twisting of the mesentery and mesenteric vessels
      • bird's beak sign: if rectal contrast has been administered
      • X-marks-the-spot sign: crossing loops of bowel at the site of the transition
      • Split wall sign: mesenteric fat seen indenting or invaginating the wall of the bowel
  • signs of impending AAA rupture:
    • large size > 7cm
    • increasing size
    • thrombus change - fissures, reduced size
    • hyperattenuating crescent
  • GIT bleeding:
    • location found by carefully looking for gradual pooling on multiphase CT
  • where is the fluid?
    • fluid behind the liver represents pleural effusion or haemothorax
    • fluid anterior to liver, in Morrison's pouch or in recto-vesical pouch/pouch of Douglas is intra-peritoneal
    • fluid between pubic symphysis and bladder is extra-peritoneal
    • fluid behind rectum is retroperitoneal
    • intermesenteric fluid in abdominal trauma suggests mesenteric and/or bowel injury - look for triangular shapes!
  • the Alfred Hospital trauma protocol in 2017:
    • split contrast bolus 70ml PV phase at 4ml/sec then 30ml NSaline at 4ml/sec then pause 20secs, then 60ml arterial phase at 4ml/sec followed by 30ml NSaline at 4ml/sec
    • oral contrast is usually NOT given as may interfere with scan interpretation and delays scan by at least 1hr
    • single CT scan thorax/abdomen

splenic injury

American Assoc. for the Surgery of Trauma (AAST) grading

  • grade 1
    • subcapsular haematoma < 10% of surface area
    • capsular laceration <1cm depth
  • grade 2
    • subcapsular haematoma 10-50% of surface area
    • intraparenchymal haematoma < 5cm diameter
    • laceration 1-3cm depth not involving trabecular vessels
  • grade 3
    • subcapsular haematoma >50% of surface area or expanding
    • intraparenchymal haematoma > 5cm diameter or expanding
    • laceration >3cm depth OR involving trabecular vessels
    • ruptured subcapsular haematoma or intraparenchymal haematoma
  • grade 4
    • laceration involving segmental or hilar vessels with major devascularisation > 25% of spleen
  • grade 5
    • shattered spleen
    • hilar vascular injury with devascularised spleen

Mx of blunt splenic injury

  • urgent laparotomy if diffuse peritonitis or haemodynamically unstable
  • angiography +/- embolisation if AAST grade IV or V with contrast blush, moderate haemoperitoneum or ongoing splenic bleeding
  • consider embolisation for AAST grades III, IV or V
ctabdo.txt · Last modified: 2017/07/08 00:03 (external edit)