Effect of small bowel transit time on accuracy of video capsule endoscopy in evaluating suspected small bowel bleeding

BACKGROUND: Obscure small bowel bleeding is defined as gastrointestinal bleeding (GIB) that is unidentifiable with esophagogastroduodenoscopy and a colonoscopy with video capsule endoscopy (VCE) being the next gold standard step for evaluation. Small bowel transit time (SBTT) is a metric of a VCE study that is defined as the time the capsule takes to travel through the small intestine. AIM: To determine if SBTT within the VCE study, correlates to overall detection of obscure small bowel bleeds. Furthermore, we attempted to identify any existing correlation between SBTT and re-bleeding after a negative VCE study. METHODS: This is a single center retrospective analysis of VCE studies performed for overt and occult GIB at Einstein Medical Center, Philadelphia, between 2015 and 2019. Inclusion criteria primarily consisted of patients 18 years or older who had a VCE study done as part of the workup for a GIB. Patients with incomplete VCEs, poor preparation, or with less than 6 mo of follow up were excluded. A re-bleeding event was defined either as overt or occult within a 6-mo timeframe. Overt re-bleeding was defined as Visible melena or hematochezia with > 2 gm/dL drop in hemoglobin defined an overt re-bleeding event; whereas an unexplained > 2 gm/dL drop in hemoglobin with no visible bleeding defined an occult re-bleed. RESULTS: Results indicated that there was a significant and positive point biserial correlation between SBTT of 220 min and detection of a bleeding focus with a statistically significant p value of 0.008. However, the area under the curve was negligible when trying to identify a threshold time for SBTT to discriminate between risk of re-bleeding events after a negative VCE. CONCLUSION: In terms of SBTT and association with accuracy of VCE finding a bleeding focus, 220 min was found to be adequate transit time to accurately find a bleeding focus, when present. It was found that no threshold SBTT could be identified to help predict re-bleeding after a negative VCE.