Abstract
Diverticulosis of the colon is a common condition, affecting more than 70% of 70-80-year-olds. However, only a small proportion will go on to develop acute diverticulitis (AD). The reason why certain individuals with diverticulosis develop complications while the majority remain asymptomatic is unclear.
It is hypothesised that the microbiome of the colon plays an important role in the aetiology of AD. This thesis aims to evaluate this theory, as well as review the published literature in special scenarios of diverticular disease sometimes encountered in clinical practise.
Chapter one provides an overview of what is already known about the human microbiome - the natural history, evaluation, and current understanding of its role in human health and disease.
The ideal specimen for assessing the colonic microbiome has yet to be established, therefore chapter two reports a feasibility study validating rectal swabs compared to stool specimens undergoing 16S rRNA gene sequencing.
Having introduced important concepts in study of the microbiome, chapter three will focus on the colonic microbiome in acute diverticulitis, aiming to establish whether microbiome profiles from individuals with AD correlate with clinical presentation, specifically focussing on complicated, or recurrent episodes of AD.
Acute diverticulitis most commonly affects older patients, therefore contemporary clinical practise guidelines for the management of AD are predominantly based on evidence derived from AD affecting the sigmoid colon in older patients – the typical presentation of AD seen in Western countries. However, AD can affect any location of the colon, at any age. Whether such “atypical” presentations represent the same entity has been debated, with implications for clinical management.
Chapter four will therefore review aspects of diverticular disease of the right-sided colon and its clinical management. The prevalence of right-sided diverticulosis in a New Zealand population has not previously been reported, this will be defined in chapter five.
Finally, the incidence of AD in patients under 50-years old has been increasing in recent years. Chapter six describes the changing epidemiology, attempts to explain the increasing incidence, and discusses aspects of clinical management that may differ in the younger cohort affected by AD.