CT abdomen

see also:

• radiology
• CT thorax / chest
• CT brain
• retroperitoneal fibrosis (RPF)

• 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
    • see https://radiopaedia.org/articles/sigmoid-volvulus
• 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!

• 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

• 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

• appendicitis
• appendiceal faecoliths
• cholecystitis
• diverticulitis
• colitis
• inflammatory bowel disease (IBD)
• appendagitis
• acute pyelonephritis
• renal abscesses and perinephric abscesses
• steatohepatitis (fatty liver)
• liver lesions - hepatic abscesses, cysts and nodules

• hepatocellular carcinoma
• stomach cancer
• colorectal cancer (bowel cancer)
• pancreatic cancer
• renal malignancies
• bladder cancer
• adrenal tumours
• phaeochromocytoma
• ovarian tumours
• uterine cancer
• lymphoma
• Pseudomyxoma peritonei (PMP or "jelly belly")