Inflammatory bowel disease is an umbrella term encompassing ulcerative colitis and Crohn’s disease as well as unclassified inflammatory bowel disease where features do not fit well into either category.
Both are chronic,
progressive inflammatory conditions resulting from inappropriate immune responses to gut microbial antigens in genetically susceptible individuals exposed to environmental triggers [1] (Fig. 2).
Ulcerative colitis is limited to the colon,
although there can be limited small bowel involvement with backwash ileitis.
It affects the bowel mucosa and submucosa.
Patients also have an increased risk of bowel malignancy.
Crohn’s can affect any part of the gastrointestinal tract and is transmural resulting in complications such as strictures and fistulae.
Both conditions have a range of extra-intestinal manifestations.
The prevalence of both conditions is highest in Europe and North America exceeding 0.3% of the population [2].
Incidence is also rising in more recently industrialized countries [2].
The mean age of presentation is in young adults with around a third of patients diagnosed before the age of 21 [3].
Therefore,
there is a significant paediatric patient population requiring appropriate investigation for these conditions.
As we will illustrate,
imaging plays a role both in the diagnosis and follow up of these patients (Fig. 3).
Patient symptoms range from diarrhoea,
bloody stools,
abdominal pain and urgency when the large bowel is affected to fatigue,
weight loss and nutritional deficiency when the small bowel is affected.
At presentation,
although initial diagnosis is usually made on the basis of clinical features as well as endoscopy and histopathology,
often ultrasound is performed as part of the work up for abdominal pain and the patient may have been referred for this by their family doctor.
If classic features of inflammatory bowel disease are seen the patient can be referred urgently for further investigation and treatment.
At diagnosis European paediatric gastroenterology guidelines [4] recommend imaging of the bowel in patients with suspected Crohn’s disease,
unclassified IBD and suspected ulcerative colitis with atypical symptoms.
Imaging of the small bowel,
which cannot be easily accessed by endoscopy,
is important to differentiate Crohn’s from ulcerative colitis; this distinction has significance in the subsequent natural history of the disease.
In addition,
imaging is required to assess the severity and extent of disease and therefore guide treatment intensity.
Once the diagnosis is made,
further imaging may be required to guide management during episodes of acute flare,
to assess for intra and extra-luminal complications or to assess for response to treatment [4].
Although medical treatment to control symptoms and inflammation is the mainstay of management,
surgery may be required in refractory cases.
Imaging also contributes to the diagnosis of some of the wide-ranging extra-intestinal manifestations of these diseases.
The paediatric population itself presents unique considerations when deciding which imaging investigations to choose (Fig. 4).
The first is exposure to ionizing radiation.
Paediatric patients have a higher surface area to volume ratio compared to adults.
As they are growing they also have a higher rate of cellular proliferation.
This results in a higher risk of cancer per unit radiation than in adults [5].
Furthermore,
as these conditions are chronic with a relapsing remitting course,
it is likely that patients will require multiple imaging investigations throughout their lifetime,
hence cumulative radiation is an important factor.
A second consideration is patient tolerance.
Paediatric patients,
particularly if young,
are less likely to be able to be positioned still for any great length of time.
In addition,
this patient group is less able to tolerate certain requisites for preparation prior to investigation,
for example invasive procedures such as cannulation or ingesting large volumes of oral contrast.