Computed tomography in gastroenterology.

Computed tomography detects mass lesions greater than 2 cm in diameter whether tumours, cysts, abscesses or granulomas but cannot usually distinguish between benign and malignant tumours or between cysts, old haemorrhage or abscess. Accurate localization, however, allows precise percutaneous aspiration or cytology. In gastroenterology it is used for disease in liver, pancreas, biliary system and spleen and, to a much lesser extent, in the gastrointestinal tract. Ultrasonography can frequently produce similar information and is much more readily available and cheaper. For tumour staging, CT is advantageous in showing all organs including soft tissues, lung, bone and subcutaneous tissue. Where ultrasonography fails for technical reasons, CT is invariably recommended and, when doubt exists as to the interpretation with ultrasonography, CT is undertaken (or vice versa). The management of malignant disease is improved by more accurate diagnosis and radiotherapy planning as well as more accurate monitoring of treatment with a non-invasive technique.