14  Abdomen CT

Reference:

14.1 Steps

  1. General axial scan

  2. Free intraperitoneal gas or fluid ?

    • Gas: (use wide window) see whether gas in bowel ?

    • Fluid: see free fluid in dependent areas (hepatorenal, perihepatic, pelvis, etc.)

  3. (Scroll down): Assess Organs

    • Liver / GB: focal lesion, duct dilatation
    • Pancreas: duct dilatation
    • Spleen
    • Adrenals
    • Kidneys: hydronephrosis, follow ureter down to..
    • Bladder:

  4. (Scroll up): Glutter

    • Lt paracolic glutter: greater omentum
    • Rt paracolic glutter: morrison pouch, subphrenic space

  5. Bowel

    • Esophagus → Stomach
    • Small bowel: (duodenum 1st - 4th) left → right “sweep”
    • Colon:
      • anus → rectum → sigmoid
      • desc.colon → splenic.flex → TV → hep.flex → asc.colon
      • cecum → terminal illeum
      • Appendix

14.2 Esophagus

14.3 Bowel

  • Diameter: small bowel < 3 cm, large bowel < 6 cm, cecum < 9 cm
Warning

Characteristic is more important than size, e.g., proximal distend, distal collapse, with transition zone suggests gut obstruction.

14.4 Biliary

  • CBD: diameter < 6 mm (if age > 60 yr, can dilate 1 mm / yrs)

14.5 Pancreas

  • Pancreatic duct diameter < 3 mm

14.6 Spleen

  • Max diameter (axial or coronal) < 12 cm

14.7 Adrenal gland

Figure 14.1: Adrenal gland (CT axial)

  • Thickness < 1 cm

  • Concave margins (look for convexity, e.g., nodules)

14.8 Renal

14.8.1 Renal protocol CT

  • Corticomedullary phase: mostly cortex enhanced

  • Nephrographic phase: mostly kidney parenchyma enhanced

  • Delayed phase: see collecting systems

14.8.2 Pyelonephritis

See Striated nephrogram Figure 14.2

Figure 14.2: Rt Pyelonephritis CT

14.8.3 Hydroureter

  • Ureter diameter > 3 mm (ref)

14.9 Lymphnodes (Abdomen)

14.9.1 Normal LN

Diameter: approx. < 1 cm in short axis, oval-shaped

14.9.2 Abnormal LN

  • Shape: Rounded
  • Heterogeneous / Cystic change