Can Radiologic Evaluation Before Capsule Endoscopy Predict Capsule Retention?

To the Editor: We read with interest the recent article published by Al-Bawardy et al. The authors presented a large cohort of 5593 cases undergoing capsule endoscopy (CE), of whom 0.3% retentions occurred and they concluded that small bowel anastomosis and obstruction may be radiologic predictors of capsule retention. We would like to commend the authors on reporting the large study and endeavoring to define radiologic findings predictive of retention. However, we believe that there are several limitations in this study to which we wish to add our consideration. First, the manufacturers of the CE were not presented in the article, as over the last decade, there were 5 types of CE, including Given Imaging (Yokneam, Israel), Olympus EndoCapsule (Olympus, Tokyo, Japan), OMOM pill (Jinshan, Chongqing, China), MiroCam (Seoul, Korea), and CapsoCam (Saratoga, CA), each of which may differ in dimension, field of view, image storing speed, and mode of data transmission. Second, in this study, computed tomography (CT) or computed tomography enterography (CTE) for patients with CE retention and for controls was compared, and CT or CTE was performed within 6 months before CE; however, the condition and patency of the small bowel may change during the period not more than 6 months, especially for those with Crohn’s disease. Third, as shown in Table 2 in their study, 2 cases were retained in the stomach of the 17 retentions, actually cases retained in the stomach can be checked with the tracking system of the CE. In our department, for cases retained in the stomach, gastroscope is used to help pushing the CE into the duodenum if the CE does not enter the duodenum within 2 hours. Finally, we do agree with the authors that careful review of surgical history and imaging before CE may help reduce capsule retention. Nevertheless, capsule retention can also occur even when the CT was normal. Conventional CT often missed the significant strictures and were poor predictors of capsule retention, CTE, and magnetic resonance enterography improving distention of small bowel may be more effective in predicting capsule retention. In summary, until now, no accurate methods can avoid capsule retention absolutely. We believe that previous radiologic evaluation before CE, such as CTE and magnetic resonance enterography, may help predict capsule retention. Further large prospective study is needed to confirm the accuracy of radiologic evaluation predictive of capsule retention.