Two contradictory studies have recently been published about gastric sleeve volume and its effect on weight loss. Both studies used three dimensional gastric computed tomography with gas expansion to measure the gastric sleeve volume after surgery.
The first study, “Dilation of Sleeve Gastrectomy: Myth or Reality?” published in Obesity Surgery showed that more than 50% of patients will have gastric sleeve dilation at one year after surgery. Dilation mainly affected the gastric tube and was not associated with increased food intake or decreased weight loss during the 18-month follow-up after surgery. Interestingly, the authors show that the smaller the gastric sleeve lumen the higher the risk of dilation. Dilation is defined in this study as more than 25% increase in total gastric volume.
The second study, “Impact of Sleeve Gastrectomy Volumes on Weight Loss Results: a prospective study”, showed that weight loss at 18 months after sleeve gastrectomy was significantly higher in small volume gastric sleeve patients. Interestingly, the authors found no correlation between gastric tube volume and weight loss. In other words, gastric antrum volume determined the extent of postoperative weight loss; the smaller the antrum the higher the weight loss at 18 months after surgery.
Gastric sleeve surgery is a metabolic procedure that alters the interaction between ingested food and the gastrointestinal tract. Gastric emptying is increased and neuro-hormonal signals emanating from the stomach and intestines are altered favoring increased satiety and weight loss. Increased gastric emptying has been demonstrated in several studies. It is mainly due to gastric fundus resection and decreased gastric compliance as well as the elimination of the postprandial gastric accommodation reflex. The antrum is the gastric pump and it does promote gastric emptying especially when ingested food is rushed from the gastric fundus into the antrum. A retained gastric fundus after sleeve gastrectomy is associated with poor weight loss and postoperative acid reflux disease. A dilated gastric tube is different from a retained gastric fundus or poorly performed gastric sleeve. I agree with the authors of both studies that as long as the gastric fundus is properly resected weight loss is not affected by overall gastric sleeve lumen size. I am also of the opinion that a narrow gastric lumen does increase the risk of postoperative reflux. Gastric antrum volume however is unlikely to affect weight loss. The antrum is made of thick muscle wall and is less likely to dilate with time. Furthermore, the antrum promotes gastric emptying and therefore a preserved antrum is more likely to be associated with better weight loss. A radical antrectomy destroys the stomach function completely and reduces the gastric function to a mere tube for food passage. At Houston Weight Loss Surgery Center, we advocate the preservation of gastric antrum and complete resection of gastric fundus. Preserving the antrum prevents against narrowing of the incisura angularis. A narrowed incisura increases the risk of acid reflux, food regurgitation, staple line leak and probably decreased weight loss.