Changes in gastric electrical activity following upper gastrointestinal surgery: The electrophysiological and histological changes that occur following upper gastrointestinal surgery

Abstract

Introduction Upper gastrointestinal surgery and hepaticopancreatobiliary surgery comprise a major subset of general surgery. While most patients recover well post-operatively, some patients unfortunately experience persistent post-surgical symptoms including nausea, vomiting, delayed gastric emptying, and reflux. Recent research has focused on the role of aberrant gastrointestinal electrophysiology in contributing to post-surgical gastric function, enabled by advances in high-resolution (HR) gastric mapping technologies. This thesis therefore aimed to better understand changes in gastrointestinal electrophysiology, relevant histology, along with relationships to symptoms and quality of life following upper gastrointestinal surgery. Methods HR gastric serosal (invasive) mapping was performed on porcine models, including healthy weaner pigs and those who underwent a formation of gastrointestinal anastomosis two weeks prior. Data on gastric slow wave frequency, velocity, amplitude, and propagation direction were analysed. Histology was used to assess Interstitial Cells of Cajal (ICC). HR body surface gastric mapping was also performed to assess the changes in gastric electrophysiology and motility following surgeries of different cohorts including oesophagectomies, sleeve gastrectomy, gastric bypass, and pancreaticoduodenectomies in human subjects. Data on gastric slow wave frequency, amplitude and meal response, were obtained and analysed. Results Normal physiological relationships between gastric slow wave parameters were defined, together with changes related to ICC loss and senescence. In the porcine model, changes in gastric frequency, velocity and amplitude were identified at 2 weeks following the formation of gastrointestinal anastomosis, with intestinal slow waves showing capability to cross through the anastomotic scar and into the stomach. There was also consistent regrowth of ICC into the anastomosis. The translational significance of these findings was demonstrated in a patient with chronic gastric dysmotility, with these abnormalities termed “Gastric Aberrant Pathway (GAP) Syndrome". In humans, abnormal gastric slow wave frequency, rhythm and other parameters were variably identified, dependent on cohort of post-surgical patients, and these changes show correlations with patient symptoms and quality of life in post-bariatric cohorts. Conclusion The results of this thesis advance the understanding of normal gastric electrophysiology, and demonstrate several novel abnormalities in gastrointestinal electrophysiology following upper gastrointestinal surgery. These insights will inform future diagnostic, preventative and therapeutic strategies for post-surgical gastric dysfunction.