Abstract
The role of the three gastric regions (fundus, body and antrum) in the emptying of nutrient and non-nutrient meals from the stomach remains unclear. Clinical routine analysis is only concerned with whole stomach emptying, whereas previous research studies have examined the behaviour of the proximal and distal stomach. The generally approved model for gastric emptying suggests that the antral mill is responsible for the trituration and subsequent emptying of solid food from the stomach. However, little is known about the contribution to liquid and semi-solid emptying patterns controlled by different regions of the stomach and regulated by other digestive mechanisms such as gastric acid secretion, despite the fact that these types of meals are considered to be essential for daily nutrition. A new method has been established for the processing and analysis of the three stomach regions which may provide more detailed physiological information regarding gastric emptying while being technically simpler and more time saving than current techniques. A series of clinical gastric emptying studies were undertaken in normal subjects, using both scintigraphy and Electrical Impedance Epigastrography (EIE) techniques simultaneously. The experiments can be divided into gastric emptying studies with different calorific meals, with placebo and a pharmacological gastric secretion blocker. The studies were carried out to establish whether useful additional physiological information can be extracted from the analysis of scintigraphic gastric images of the emptying patterns for simple and complex meals using the three regions of interest method. Furthermore, the study investigated the effect of inhibiting gastric secretion on the rate of liquid and semi-solid emptying from the three regions of interest. The outcome may help in understanding the digestive processes and lead to a better diagnosis of gastric disorders as well as localising the pathophysiological mechanisms that cause a delay in gastric emptying in a specific region of the stomach. The nutrient meal experiments showed that the antrum has the shortest half-emptying time (T50) while the emptying times of the fundus and body were longer. Moreover, the emptying pattern of the fundus, body and antrum varies according to the nutrient content of the meal. It is well known that increasing the calorific content of the meal delays the total gastric emptying. However, these studies demonstrated that the largest delay generally occurs in the fundus and body, where the majority of gastric juices are secreted. Mixing complex meals with these secretions and stimulating the digestion process takes longer than a simple meal resulting in the significant delay in the fundus and body. Conversely, a greater delay in the antral emptying was found predominantly in simple meals for the control of emptying. Large quantities of simple meals were found to trigger the return of duodenal contents back to into the pyloric area, consequently causing a delay in the liquid emptying time of the antral region of interest (ROI). Therefore, since it is thought that the gastric fundus and body may play an important role in the emptying of semi-solids, the semi-solid emptying time may not represent the volume of the meal within the antrum but instead represent the amount of processed food particles only. The scintigraphic tri-region method uses the same total region of interest allowing for the acquisition of three acceptable regional images of the stomach. Experimental investigation has shown that the tri-region method is clinically useful to outline the function of each division of the stomach individually, as well as studying the impact of gastric secretory behaviour in each division. Therefore, the tri-regional model provides a better understanding of the physiology of the three gastric regions. In conclusion, the tri-regional model has confirmed that gastric function is related to gastric acid secretion and that the epigastric impedance reflects the gastric acid secretion as well as the meal composition and gastric content volume.