What is Inflammatory Bowel Disease (IBD)?

Crohn's disease and ulcerative colitis are Iife long gastrointestinal disorders collectively known as Inflammatory Bowel Disease (IBD).  

The conditions are an emerging global disease, with New Zealand having one of the highest prevalence in the world.   It is estimated that nearly 20,000 New Zealanders live with these conditions. Although can occur at any age, most common age of diagnosis in childhood is in early adolescence – from around 12 or 13 years.  The conditions are becoming more prevalent, more severe and more complex and are being diagnosed in more and more very young patients.

The Inflammatory Bowel Diseases (IBD) are chronic inflammatory conditions of the gastrointestinal (GI) tract and comprise two main types - Crohn’s Disease and Ulcerative Colitis.

Crohn’s disease (CD) can involve any part of the GI tract, from the mouth to the anus. CD typically features transmural inflammation and skip lesions. The presence of granulomata on histology is a feature seen in CD but not UC.

Ulcerative Colitis (UC) typically involves the colon extending proximally from the rectum for a variable distance. Inflammatory changes in UC are superficial and continuous. UC is less common than CD in children.

In addition, the term IBD-Unclassified (IBDU) is used when children clearly have IBD, but the biopsy or other results are not able to clearly distinguish between CD and UC at that time. It usually becomes clear over time whether this is actually CD or UC.

What is the cause of IBD?

The precise cause of IBD is not clear. Three important factors are involved in causing IBD: genes, bacteria and innate immune system responses in the digestive tract. IBD likely occurs in people with a certain combination of genes: these genes alter the defences in the surface of the bowel, leading to a different response to bacteria in the intestines, resulting in uncontrolled inflammation. Certain genes are important in early-onset (paediatric) IBD.

What is important about paediatric IBD?

Over the past decades IBD has become increasingly common around the world. CD, in particular, is now seen much more frequently. Initially these changes in the pattern of IBD were seen in “western” countries, but more recently increased rates of IBD have also been seen in other countries. As well as becoming more frequent overall, IBD is now also occurring more commonly in younger children.

IBD in children differs greatly from adult onset disease in many ways, including disease location and patterns. For example, the majority of children with UC have pan-colonic involvement at diagnosis and few children have isolated proctitis. In children with CD, upper gut involvement in CD is also seen much more commonly than in adults (60% vs 5%).

IBD in children and adolescents commonly impacts upon growth, nutrition and pubertal development. Almost all children with CD and at least half of children with UC have poor weight gain or weight loss prior to diagnosis. Children with UC and CD may also have impaired linear growth at diagnosis or subsequently. This may lead to a reduction in final adult height. Furthermore, because IBD commonly causes problems during adolescence, it may impact upon the onset and progression of puberty. These factors influence the key aspects of the management of IBD in children and adolescents.

How does IBD present in children? 

Children with IBD can have a wide range of symptoms before diagnosis. Common symptoms in children with Crohn’s disease are abdominal pain, diarrhoea, and weight loss. The most common symptom in children diagnosed with ulcerative colitis is diarrhoea with blood. However, children can have a number of other symptoms before diagnosis. These include losing weight, not getting taller, mouth ulcers, rashes, sore joints, lethargy, anaemia, iron deficiency and lip swelling. Some children will just have trouble getting taller without any bowel symptoms, whilst others will just have tummy symptoms. Considering IBD as a potential cause for various symptoms is important.

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