In this study, we examined the validity of our modification on the passage criteria suitable for daily clinical practice and evaluated the safety and usefulness of PC in our consecutive patients. Our main findings were as follows. The overall patency rate was 95.1%, 41 (12.6%) patients were judged as having estimated patency, and SBCE was performed safely. In addition, 32.5% of the participants needed CT judgement. According to our passage criteria, one (0.3%) SBCE case resulted in capsule retention because of a false CT judgement. Multivariate analysis revealed that established CD and inpatient were the factors independently related to patency loss (P < 0.05). Therefore, our modification on the passage criteria tailored for daily clinical practice seemed to be reasonable, keeping in mind CT misjudgement.
One of the main purposes of this study was to determine whether ‘estimated patency’ without retesting is valid in identifying patency for SBCE. Premature dissolution of the AgileTM patency device was reported to occur, with at least an incidence of 1.3% in Europe, possibly the cause of unexpected capsule retention [24]. This event was recognised by the detection of a persistent radiofrequency signal after radiological imaging had failed to identify the patency device. In Japan, patients who need to undergo a patency-testing procedure can avail insurance if an intact capsule or intact body with an eroded timer plug is directly detected or if PC entry into the colon is confirmed by X-ray or another imaging modality at 30–33 h after ingestion [17]. However, PC retesting is clinically difficult because it impairs the proper timing of the examination and patient acceptability. In this study, no case of SBCE retention in ‘estimated patency’ was found, suggesting the validity of our judgement method.
Another purpose of this study was to determine the validity of plain CT judgement after confirming the location of the PC inside the body. Candidates for the second imaging modality include plain or contrast-enhanced CT [25], low-dose CT [18], X-ray tomography [19], abdominal ultrasonography [20], air enema and magnetic resonance imaging. Among them, plain CT is an objective method and is the easiest to use in Japan, although it exposes patients to radiation. In this study, capsule retention occurred in one (0.3%) patient. This result seems to agree with the results of a recent large-scale multicentre study in Japan [21]. Our results suggested that the choice of plain CT as the second imaging modality is nearly valid. However, a misjudgement of CT was observed in one case. Other studies also revealed that CT misjudgement would be a non-negligible reason for SBCE retention after PC examination [21, 23]. Physicians performing PC examinations should be aware of this issue.
Moreover, multivariate analysis indicated that age, female and inpatient were the factors independently associated with PC excretion within 30 h, and established CD and inpatient were the factors independently related to patency loss (P < 0.05). CD is a recognised factor related to patency loss, consistent with our results [26]. However, many reports indicated that inpatients are related to transit time but not to patency loss. Although the exact reason for this discrepancy remains unknown, our results showed that inpatients were more likely to have organic disorders, such as radiation enteritis and NSAID-induced small-bowel mucosal injury. In addition, patients with impaired functional passage of the upper gastrointestinal tract might have been included. Physicians should also be aware that SBCE has a longer small-bowel transit time in the elderly and women, regardless of having patency loss.
Although the safety and usefulness of PC have been reported in larger-scale prospective studies in Japan [5], the methods may need to be modified in daily clinical practice. Watanabe et al. reported that extending the time to confirm functional patency to 72 h might be acceptable and increase the possibility to perform CE safely [23]. Meanwhile, Omori et al. reported that the 24-hour assessment method can be handled more easily and more useful clinically [22]. Our modification in this study also proposes a highly feasible use of PC in daily practice.
This study has several limitations. Firstly, it is a single-centre, single-arm, retrospective study, although the participants were consecutive patients in clinical practice. Secondly, the overall patency rate was high in this study because we included many patients with OGIB in addition to CD. Therefore, the number of cases might be statistically insufficient for the analysis of factors related to patency loss. Despite some limitations, our study certainly suggests that our modified criteria play a role in the real-world use of PCs in actual clinical practice. A prospective comparative study with a larger sample size and in multiple centres is required to verify these issues.