Is Fasting a Necessary Preparation for Abdominal Ultrasound?

INTRODUCTION Optimum conditions for the ultrasonic examination of the abdominal organs require a fluid-filled gall bladder and as little gas in the gastrointestinal tract as possible [1]. In addition the thin patient is easier to examine than the fat patient since higher-frequency transducers can be used which improve resolution. Most ultrasound (US) departments instruct their patients to come fasting for such examinations, sometimes for as long as 12 hours, assuming that the gall bladder would otherwise be contracted and difficult to assess and that fasting patients will have less gas in the duodenum & colon. Vogel et al [1] have reported favourable results with a two-day low calorie diet, laxatives and fasting. Other groups have found gas reducing agents to be of no value [2]. Some investigations have found a barium meal or upper gastrointestinal series does not interfere with abdominal US although the US images, especially of the liver and gall bladder [3,4] were poor after barium enema.