The measurement of proximal, distal and total stomach emptying rates using radionuclide methods

Abstract

In this thesis, the development of a radionuclide method for the measurement of proximal, distal and total stomach emptying rates is outlined. The technique enables the simultaneous measurement of both solid and liquid emptying using a single scintillation camera/computer system. The standard solid meal comprises 1009 of ground treef containing invivo-labelled 99mTcchicken- liver and 150 ml of dextrose containing 113mJ¡-p1p¿ The potential sources of error in the measurement of g:x¡tric emptying using radionuclide methods are discussed. In normal subjects, variations in tissue attenuation caused by the changing depth of radionuclide within the stomach accounted for large enors in the measurement of gastric emptying. A new technique for correction of attenuation, which uses factors derived from a lateral image of the stomach, is described. The method was validated in phantom and human studies. The reproducibility of the method was assessed and the dåy-today variation in gastric emptying was not significant for any measured parameter. Intragastric distribution and emptying $'ere assessed in normal subjects using a new method for defining proximal and distal stomach - this method utilises a proximal stomach 'reservoir' area, seen immediately after ingestion of solids, to define the proximal stomach region. Redistribution of solid from proximal to distal stomach was a significant oomponent of the delay in emptying (lag period) in most subjects. Considerable intersubject variability in the rate of redistribution was also observed. In a study with combined manometry, gastric emptying of solid was slowed by duodenal lipid infusion. This slowing was associated with (1) suppression of antral and proximal duodenal motility, (2) stimulation of isolated pyloric pr€ssure waves (IPPV/s) and (3) redistribution of food ftom the distal to the proximal stomach. The effe¡t of alterations in the calorie oontent of a meal on gastric motility and emptying was also assessed. Liquids redistributed rapidly within the stomach and emptied after a minimal lag period. Dextrose delayed liquid emptying when compared with saline - this delay was associated with (1) increased retention of liquid in the distal stomach, (2) an increase in IPPWs and (3) suppression of antral waves. Solid emptying was slower than liquid emptying and wæ characterised by a lag period, followed by approximately linear emptying. Dextrose delayed gastric emptying of solids by increasing proximal stomach retention and increasing the lag period. In conclusion, the new technique described in this thesis is reproducible and sensitive to phpiological changes, and can be used, not only for routine clinical studies, but also for experimental investigation of the me¡hanisms of gastric emptying in normal and pathological subjects.