Liquid gastric emptying assessed by direct and indirect techniques: radionuclide labelled liquid emptying compared with a simple paracetamol marker method.

Radionuclide techniques have enabled direct quantitative measurements of gastric emptying for solid and liquid phases of a meal. Such a technique has been used to validate the use of plasma paracetamol levels as a means of indirect assessment of liquid gastric emptying and to confirm a useful correlation exists between plasma and saliva paracetamol concentrations. Ten healthy volunteers underwent a routine gastric emptying study. The meal comprised a 100g 'hamburger' and 150 ml of 10% dextrose in water containing 113In and 1 g of dissolved paracetamol. The time taken for 50% of the liquid marker (T50) to clear the gastric region was assessed. Time to peak concentration of paracetamol for both saliva (C max-saliva) and plasma (C max-plasma) was determined. A significant correlation was found between the time to C max-plasma and T50 (rs = 0.624, P less than 0.05) and also time to C max-saliva and T50 (rs = 0.573, P less than or equal to 0.05), confirming that paracetamol concentration in plasma and saliva reflect radionuclide assessed liquid emptying. A useful correlation also exists between time to C max-plasma and time to C max-saliva (rs = 0.84, P less than 0.01) permitting them to be used interchangeably. The use of time to C max-saliva to assess liquid gastric emptying has a number of applications.