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Imai et al. Mini-invasive Surg 2024;8:2 https://dx.doi.org/10.20517/2574-1225.2023.67 Page 7 of 8

Although most of our patients had a history of surgery, one (1/18, approximately 5%) did not have a history
of abdominal surgery and was diagnosed with a small bowel tumor. However, our study may have
overestimated the frequency of small bowel tumors as most of our patients had a history of surgery.
Furthermore, one patient with Meckel’s diverticulum on capsule endoscopy had a history of catheter
insertion for peritoneal dialysis. Interestingly, CT and capsule endoscopy revealed variable findings in our
study, which may be attributable to the small sample size. We speculate that the cause of small intestinal
obstruction is typically related to the small intestinal tract; thus, endoscopic visualization of the small
intestinal lumen might be more important for determining the cause of obstruction than contrast-enhanced
CT-based evaluation of the surrounding regions. Therefore, capsule endoscopy may be useful for patients
with an unclear cause of obstruction on CT. Nevertheless, CT is the gold standard investigation for the
diagnosis of small intestinal obstruction and provides useful information. Additionally, the resolution of CT
has significantly improved over time. Randomized clinical trials are needed to compare the diagnostic
performance between CT and capsule endoscopy for small intestinal obstruction.

It is crucial to accurately determine small intestinal patency before performing capsule endoscopy. In the
present study, X-ray could not detect small intestinal patency in all patients. Previous large-scale studies
have demonstrated that approximately 30% of patients require CT to determine the small intestinal
patency [10,11] , which is consistent with our results. Compared with X-ray, non-contrast CT can accurately
distinguish between small and large intestines and can identify patency capsules in the colon. Therefore,
non-contrast CT should be considered in cases where the patency capsule cannot be identified on X-ray.
Patency capsules are associated with important adverse events. A previous study demonstrated that the
outer wall of the patency capsule remains undissolved in patients with Crohn’s disease, which can lead to
[12]
small intestinal obstruction .

The main strength of the present study was that it was a prospective observational study that evaluated the
cause of small intestinal obstruction in patients with a high risk of obstruction recurrence. However, this
study also had several limitations. First, the sample size was small; Second, we did not compare the
diagnostic accuracy between capsule endoscopy and other investigations; Third, the follow-up duration was
short. Finally, most patients had a history of surgery. Therefore, our findings have limited generalizability to
the general patient population and those without a history of abdominal surgery.

In conclusion, capsule endoscopy and subsequent balloon endoscopy, after confirming the intestinal
patency, revealed the cause of obstruction in our small patient population. Capsule endoscopy may be
useful for these patients after the obstruction has been relieved. However, further large-scale comparative
trials are needed.

DECLARATIONS
Acknowledgments
We thank all patients and their families.

Authors’ contributions
Conceptualized the trial design: Niikura R, Yamada A
Collected the data: Niikura R, Yamada A, Suzuki H, Nakada A, Mitsuno Y, Yamamoto S
Analyzed the data and drafted the manuscript: Imai M, Niikura R
Edited the manuscript: Imai M, Niikura R, Aoki T, Hayakawa Y, Kawai T, Fujishiro M
All authors approved the final version of the manuscript.