Methods for the assessment of gastric emptying in humans: an overview.

A number of different methods are used for the measurement of gastric emptying in humans, and all have some advantages and disadvantages. The method of choice will depend on whether solid or liquid meals are to be studied, the level of precision required, the degree of invasiveness that the subject or patient will tolerate, ethical considerations, and the facilities available. It is easier to measure the emptying of liquid meals, but the emptying of solid meals is the true reflection of what happens during normal life, and is therefore of more clinical importance. Scintigraphy, with appropriate labelling of the test meal components and appropriate corrections applied to the images obtained, is the method of choice for clinical investigation of disturbed emptying patterns and can be applied to solid or liquid meals, but its application is limited by the need to restrict exposure to ionizing radiation. The double sampling gastric aspiration technique allows serial measurements of the composition of the gastric contents and of the volume and composition of gastric secretions but can be used only with liquid meals. Other imaging techniques (ultrasound, MRI) and epigastric impedance measurements produce results that correlate well with those obtained by scintigraphy or aspiration. MRI has the unique feature of allowing the physician to follow gastric emptying while at the same time being able to observe any morphological abnormalities which may contribute to abnormal gastric function. Tracer methods, such as following the appearance in blood of paracetamol, may be useful for screening purposes in large populations. Regardless of the method used, the investigator must be aware of the large interindividual variability which exists in the rate of gastric emptying in normal healthy individuals and of the factors known to influence the gastric pattern.