Renata Szépeová, Zuzana Havlíčeková, Peter Bánovčin
Inflammatory bowel diseases (IBD) are classically divided into Crohn‘s disease (CD) and ulcerative colitis (UC). However, these two entities are still heterogeneous and a further classification into sub-phenotypes is necessary. Clinical division into sub-phenotypes is easy to use, do not necessitate complicated tests and can already give very important information for management of patients. In CD, clinical sub-phenotypes are based on the age at diagnosis, disease location and disease behaviour. Age at diagnosis allows to differentiate CD to paediatric, classical young adult onset and more seldom CD of the elderly. These categories are associated with a different risk of development of complications and might have different pathophysiology. Classification according to disease development including stricturing, penetration or uncomplicated disease may have an impact on response to medical treatment and need for surgery. Finally the classification based on location is particularly relevant since it has been associated with different types of complications. Particularly ileal disease has been associated with the risk of surgery and colonic (particularly rectal) disease, with the risk of anal disease. In UC, the classification to sub-phenotypes is based on disease location, distinguishing proctitis, left-sided colitis and extensive colitis. This sub-classification has also a very significant clinical relevance since extensive colitis has been associated with and increased risk of colon cancer, colectomy and in some studies even with higher mortality. The Montreal Classification of IBD has several weaknesses with respect to classification of children. The dynamic features of paediatric disease phenotype (changes in disease location and behaviour over time, growth failure) are not sufficiently captured by the current Montreal Classification.