Gallstones in custard

BMJ 2003; 327 doi: (Published 27 November 2003) Cite this as: BMJ 2003;327:1270
  1. Brian Witcombe, radiologist
  1. Gloucestershire Royal Hospital, Gloucester

    Most recipes are not inventions. The Delia Smiths of this world don't invent new recipes in the scientific sense of the word. They take a known mix and add a bit more garnish here, a few herbs there, and, if successful, promulgate the new recipe under their name, t be passed on from friend to friend and generation to generation. The stimulus for the activity may be an important dinner party, a new boss to impress, or, in the case of professional chefs, a new book or television programme to fill. The stimulus for our recipe was an invitation from a retired professor of bacteriology, the chairman of a local medical and scientific society, to contribute to a Saturday exhibition for the general public in the Corn Hall of nearby Cirencester by showing how we use ultrasonography to visualise the gall bladder.

    We made a few posters, arranged to borrow a portable ultrasound machine, and set about making an ultrasound “phantom.” Making an artificial gall bladder was straightforward. A few pebbles from my drive in a party balloon partially inflated with water served the purpose. To my wife's annoyance, I then spent several evenings messing up the kitchen stove with gelatine trying to perfect the surrounding medium. The best medium was children's jelly (orange flavoured) with half the normal quantity of water; orange flavoured is a little more transparent than blackcurrant. I allowed a few cupfuls to set in a transparent container, placed the “gall bladder” on top, added further liquid jelly, and let it all set in the fridge. The jelly was transparent enough for the gall bladder to be seen within, and ultrasonography could reveal the pebbles as echogenic structures in the echo-free “bile” with acoustic shadowing. I embellished the phantom with plums, olives, and bits of metal from the garage, but the next step, even if I say so myself, was a stroke of genius.

    I made two more phantom gall bladders and immersed one in custard and another in Angel Delight (a commercial form of mousse). The gall bladder in custard was shown less well by ultrasound than the one in jelly because of fat globules in the milk, and, because of the air bubbles caught up in the mix, the gall bladder in Angel Delight could not be detected at all. The three phantoms graphically demonstrated how ultrasound can show things the eye cannot see but that fat and air interfere with the transmission of sound.

    The exhibition contained exhibits from eminent haematologists and immunologists, professors from Cranfield, and academics from Oxford. Several hundred members of the public attended. It is with pride that I tell you, even though things got pretty sticky by the end of the afternoon, the most popular exhibit was gall stones in custard. If you want, feel free to pass the recipe on to your friends.

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