Initial screening blood tests should include a full blood count, erythrocyte sedimentation rate (ESR), C reactive protein, serum urea and creatinine, serum albumin, liver function tests, and in certain instances a coeliac antibody screen. Characteristically inflammatory bowel disease is associated with a fall in haemoglobin and albumin, and a rise in platelet count, ESR, and C reactive protein levels.
23 These findings are however not always present, with UC having been reported with a normal haemoglobin, platelet count, and ESR.
24 Anti‐saccharomyces cerevisiae antibodies (ASCA) and anti‐neutrophil cytoplasmic antibodies (ANCA) may be elevated in Crohn's disease and ulcerative colitis respectively, with a diagnostic sensitivity between 60% and 80%.
25,26The differential diagnosis is wide (box 1). Infectious causes of enteritis or colitis need to be excluded. Given the rise in tuberculosis in the UK this should be considered.
A full colonoscopy with intubation of the terminal ileum, and multiple biopsies of all segments of the colon (plus terminal ileum) is now considered essential by most paediatric gastroenterologists.
27 This approach increases the diagnostic yield and improves the diagnostic certainty when compared with a more limited recto‐sigmoidoscopy.
28 For the same reasons an upper endoscopy has also now been advocated (IBD working group of ESPGHAN 2005). The macroscopic and histological appearances of the upper gastrointestinal tract (for example, the presence of apthoid ulcers or giant cell granulomas) may confirm the diagnosis of Crohn's disease in up to 25% of cases.
29 Crohn's disease can affect any part of the gastrointestinal tract, and a patchy inflammatory process is common, whereas in ulcerative colitis inflammation is usually localised to the colon with inflammation typically extending proximally from the rectum, although rectal sparing has been reported.
30Assessment of the small bowel is traditionally considered to be best performed radiologically with a barium meal and follow through, or by enteroclysis with intubation of the duodenum. This can identify small bowel pathology beyond the reach of the endoscope and better define the disease extent and presence of complications such as strictures or fistulae.
31 If endoscopic and histological evidence allow a definitive diagnosis to be made, contrast studies may not be necessary, but are always indicated in children with diagnostic uncertainty (for example, failure to intubate the terminal ileum, indeterminate colitis) or suspicion of proximal small bowel disease, long segment ileal disease, or stricture.
Box 1: Important differential diagnoses to consider during diagnostic work up of inflammatory bowel disease
- Infection
-
Campylobacter
-
Salmonella
-
Shigella
-
Yersinia
-
Amoebiasis
-
Tuberculosis
-
Clostridium
-
Giardia
- Eosinophilic gastroenteritis
- Vasculitis and autoimmune conditions
- Cows' milk/allergic colitis
- Immunodeficiency states (e.g. chronic granulomatous disease)
- Solitary rectal ulcer syndrome
- Benign lymphoid hyperplasia
- Intestinal lymphoma
Several other methods of assessing, in particular the small bowel, which involve less or no radiation exposure have been reported, although as yet none has achieved universal acceptance. For example capsule endoscopy may become more widely used in cases where a stricture has been excluded.
32 This approach cannot however replace endoscopy since histological assessment is required. Gadolinium enhanced magnetic resonance imaging or magnetic resonance imaging enteroclysis can also be used to assess the small intestine.
33 Ultrasound is another attractive option since it is often more readily available, avoids irradiation, and may reveal colonic or ileal (particularly terminal ileal) wall thickening or inflammation.
34 It may however miss mild inflammatory changes. Technetium labelled leucocyte scintigraphy may also identify intestinal inflammation, but there are concerns as to its sensitivity and specificity.
35