Gallstones and cholecystitis
- US = IOC: echogenic foci with posterior acoustic shadowing, gravity‑dependent mobility ("rolling stone"), WES (wall–echo–shadow) / double‑arc shadow sign (contracted GB full of stones); sludge (no shadow; "tumefactive sludge").
- Stones: cholesterol (commonest, radiolucent), mixed (commonest overall in many series), pigment (haemolysis); ~10–15% radio‑opaque; Mercedes‑Benz sign (gas‑filled fissures in a stone on radiograph/CT).
- Acute calculous cholecystitis (US): impacted stone at the neck, wall thickening > 3 mm with striated/halo oedema, pericholecystic fluid, distension, sonographic Murphy's sign (highest PPV with stones). HIDA: non‑visualisation of the GB at 60 min/after morphine (most specific); rim sign = gangrene. CT: stranding, wall enhancement, "hazy mesentery = inflamed organ"; complications.
- Emphysematous cholecystitis (diabetics, Clostridium): gas in wall/lumen (CT best) → emergency. Gangrenous: intraluminal membranes, asymmetric wall. Acalculous: ICU patients.
- Mirizzi syndrome: stone in the cystic duct/Hartmann's pouch compressing the CHD.