Efficacy and Safety of Bowel Preparation for Patency Capsule in CD Patients Who Previously Failed Patency Capsule

Crohn's disease (CD) involves the entire length of the gastrointestinal tract, including a large proportion of patients with small bowel involvement. Most of the small bowel length is not accessible by conventional endoscopy for diagnosis and routine follow-up. During their lifetime these patients require repeated evaluation of disease activity and extent. Traditionally this evaluation is achieved by periodic CT or MR enterography that involves repeated exposure to radiation and contrast materials and does not provide good mucosal assessment. The use of video capsule endoscopy (VCE) among CD patients provides a good mucosal assessment without exposure to radiation or contrast material, or the risks of conventional endoscopy and sedation.

The caveat of VCE in CD is the concern of capsule retention due to strictures which are sometimes asymptomatic. This is more pronounced in patients with clinical or radiographic features implying small bowel obstruction: stricturing /fistulizing disease phenotype, abdominal pain and bloating after meals, improvement with liquid diet, stenosis and proximal dilatation on imaging studies. In these high-risk patients a patency capsule (PC) test is recommended prior to VCE. The PC is a capsule in similar dimensions to that of the VCE which contains radio-opaque components and a cellophane coat that dissolves after approximately 30 hours. Patients failing to pass the pill after 30 hours continue assessment with plain abdominal X-ray imaging or a dedicated scanner in order to confirm or deny PC expulsion. If the test is positive and the PC was not expelled, the recommendation is to avoid VCE use and limit the patient to periodical imaging and conventional endoscopy as mentioned earlier. The probability for a positive PC test is 20-30% in high risk CD patients and thus, paradoxically, some of the patients who may benefit the most from VCE, will not undergo it. Nevertheless, VCE retention rate is estimated to occur in \~ 2% of patients. However, both PC and VCE are considered safe procedures and complications even in case of capsule retention are rare.

Given that the normal transit time of the entire digestive tract is up to 72 hours, delayed expulsion of the PC (i.e. >30 hours) can simply be due to slow transit or large amount of content in the large bowel and not a small bowel obstruction. Currently there are no guidelines regarding PC preparation protocol, but It seems slow transit can probably be overcome by bowel preparation.

In the endoscopic capsule unit of the TLVMC, we implement routinely a second attempt for bowel preparation, in CD patients who fail their first attempt to pass the capsule. Studies evaluating the safety and efficacy of this protocol is lacking.