Document Type

Theses, Masters


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence



Publication Details

Thesis submitted to the School of Physics, Technological University Dublin, in partial fulfilment of Degree of Masters of Philosophy, 2015.


A review of patients who underwent a hydrogen breath test for Small Intestinal Bacterial Overgrowth, following an oesophagectomy or gastrectomy was carried out in the Gastrointestinal Function Unit, St. James’s Hospital, Dublin. The aim of this research was to look at the incidence of Small Intestinal Bacterial Overgrowth and create an optimal protocol for Hydrogen Breath Testing with the hope of improving patient compliance and reducing clinic waiting times. Factors such as lifestyle, multimodal therapy, tumour morphology, and gender were analysed in relation to positive Hydrogen Breath Test results in this patient group. Patients were selected following a referral from the upper GI Surgical team. Exclusion criteria included those patients whom had complicated upper major GI surgery, those patients that had their surgery for a non-malignant carcinoma, and those patients that had their surgery for achalasia or a gastric fistula. Following a strict 12 hour fast and following pre-procedure instructions, the patient’s hydrogen breath test was conducted. A preliminary mouth rinse with a chlorhexadine agent was performed followed by a baseline breath sample. A solution of glucose or fructose was consumed and samples were taken every 15 minutes over a two hour period. The patient performed this manoeuvre by holding their breath for approximately 10 seconds and exhaling into the Gastro+ Gastrolyzer® breath monitor. Values were measured in parts per million. Poor lifestyle factors did not have an effect on the outcome of Hydrogen Breath Test results. Those patients who had a history of previous malignancy and post-operative complications showed a higher tendency towards a positive glucose Hydrogen Breath Test result as did those patients who had a longer post-operative hospital stay. This however, was not statistically significant. The percentage of patients who were positive for Small Intestinal Bacterial Overgrowth (53% in total) was greatest 6-12 months post-surgery. This may be attributed by the fact that intestinal motility including Migrating Motor Complexes can take up to 12 months before it is restored to its normal functioning state. The positive patient group tested using glucose substrate demonstrated a 93% positivity for SIBO at 60 minutes. Therefore, this suggests that altering the protocol of testing from 2 hours to 60 minutes should be considered Some patients (up to 10%) are non-hydrogen producers, those who are very symptomatic with negative Hydrogen Breath Tests should be considered for bile acid malabsorption investigation using SeHCAT (tauroselcholic [75 selenium] acid). SeHCAT is now available in St. James’s hospital to investigate patients who are symptomatic with steatorrhoea/diarrhoea post-surgery. Small Intestinal Bacterial Overgrowth can be the cause of bile acid malabsorption, therefore it should be considered to treat it with antibiotic therapy and assess clinical response before commencement with prescribed bile acid sequestrants.