Pathogenesis of diverticulosis and diverticular disease

Diverticulosis is defined by the presence of diverticula due to herniation of mucosa and muscularis mucosa through the muscularis propria at sites of vascular penetration in the colon and is asymptomatic in the vast majority affected. There are global differences of distribution, in Western industrialized societies, the most common site is in the left colon, but in Asia right sided diverticulosis predominates. Whilst present in 17.5% of a general population and 42% of all comers at endoscopy it is seen in 71% of those aged ≥80 years. Diverticular disease is defined as clinically significant and symptomatic diverticulosis, which may have an absence of macroscopically overt colitis and in true diverticulitis there is macroscopic inflammation of diverticula with related acute or chronic complications. Whilst overall, diverticulitis affects only 4% of those with diverticulosis, in younger patients (aged 40-49 years) this peaks at 11%. Diverticulosis is one of the most common chronic diseases, yet research in this field on pathogenesis has lagged behind other common conditions such as diabetes mellitus. However, in the last decade there have been major advances in taxonomy that can be used to relate to patients' outcome and treatment in both medicine and surgery. It has been shown there is an association with age, diet, drugs and smoking. Genetic studies have shown a familial association and a specific gene, TNFSF 15 may predict severity of disease. The role of the microbiome has been explored and microbial and metabolomic signatures are also important in predicting disease severity. That diverticulosis is a chronic disease is shown by mucosal pathology with subtle chronic inflammation present in those with asymptomatic diverticulosis and inflammation may lead to muscular hypertrophy, enteric nerve remodeling with disordered motility. The diverticulitis quality of life instrument shows that this condition impacts markedly on patients' well-being and prevention and amelioration of complications should be the aim of treatment and further research to attain this goal is needed.