Role of Capsule Endoscopy in the Evaluation of Mucosal Changes During Treatment of Patients With Active Crohn's Disease

Crohn's disease is a chronic, inflammatory disorder affecting any part of the gastrointestinal tract but the terminal ileum is the most frequent location involved alone or in combination with other locations. While about one half of patients have involvement of the ileum and large bowel, another third have disease limited to the small bowel.

The disease affects populations around the globe and occurs at any age but tends to have a peak incidence between the ages of 15 and 35. Typical presenting symptoms include abdominal pain and diarrhea. The clinical presentation of Crohn's disease fluctuates throughout the course of the disease. Symptoms and signs usually correlate with mucosal inflammation. The pattern of Crohn's disease viewed on endoscopy has been characterized and is associated with a number of mucosal characteristics such as erythema, swelling, nodularity, strictures, aphthoid ulceration and ulcers of variable size and depth.

The utility of capsule endoscopy in diagnosing small bowel (SB) Crohn's disease has been demonstrated in a number of studies. Diagnostic yields of 70% have been reported in suspected SB Crohn's disease. In patients with a known Crohn's disease, the superiority of the capsule to detect mucosal lesions of the SB in comparison to any other radiologic technique has also been clearly demonstrated.

A number of studies indicate that mucosal healing is a good predictor of long term remission. In particular, intense therapeutic regimens including purine analogues and biologic therapies like infliximab have been associated with endoscopic mucosal healing. The recently published SONIC trial evaluated the efficacy of infliximab monotherapy, azathioprine monotherapy and the two drugs combined in moderate to severe Crohn's disease patients. Patients who were treated with infliximab monotherapy and with the combination therapy had significantly longer corticosteroid-free clinical remission than those receiving azathioprine alone. Furthermore, mucosal healing, defined as the absence of mucosal ulcerations at week 26, was greater for the combination therapy than each of the monotherapies alone. Based on the results of these studies, obtaining a mucosal healing becomes in clinical practice a new therapeutic objective especially in patients treated by immunosuppressors or anti-TNF-alpha antibodies. In most of the studies, a complete mucosal healing was assessed by the complete disappearance of ulceration. An endoscopic response could be evaluated by the variation of several endoscopic scores of severity, that are either dedicated to the terminal ileon (TI) more the colon i.e. the Crohn's disease endoscopic severity index (CDEIS) or to the SB i.e. the Lewis score. Concerning the evaluation of the mucosal lesions of the SB by the capsule, a new index of severity is being developed in a study conducted by the different centers of the GETAID i.e. the CE-CDEIS. This score will be available in the first semester of 2013 and would be usable for the present study.

Unfortunately, the assessment of mucosal healing by conventional ileocolonoscopy is not complete since it does not allow exploration of the small bowel beyond TI. Thus, while mucosal changes and symptomatic improvement in subjects with SB Crohn's disease (with or without colonic involvement) can be inferred from studies like ACCENT I, direct evidence of the healing of the majority of the small bowel is lacking. In addition, correlation between evidence of mucosal healing and symptoms, as measured by the Crohn's Disease Activity Index (CDAI), has not been found reliable. This may reflect the limitation of viewing the full extent of small bowel ulcerations on the limited examination which is possible with ileocolonoscopy. This may potentially be overcome with the use of capsule endoscopy of the small bowel.