Patency Capsule

What is this foreign body in the abdomen? • Xray of the Week

Figure 1. What is this foreign body in the abdomen?

Figure 2. Plain abdominal radiograph at approximately 30 hours after ingestion of patency capsule. A radio‑opaque foreign body (~26 mm × 11 mm) is noted in the abdomen, consistent with retained patency capsule. Subsequent cross‑sectional imaging localized the capsule to the distal small bowel, confirming incomplete luminal patency and precluding capsule endoscopy.

Figure 3. Enlarged and abdomen radiograph demonstrates foreign body consistent with Patency Capsule in the bowel.

Patency Capsule: Imaging Appearance and Clinical Utility

The patency capsule is a dissolvable, radio-opaque capsule used to assess small bowel patency prior to capsule endoscopy. It is particularly important in patients at risk for strictures, such as those with Crohn disease or a history of abdominal surgery [1,3]. The capsule is similar in size to a standard video capsule (approximately 26 mm × 11 mm) and contains a barium-impregnated lactose core, sometimes with an RFID tag for scanner detection [1,2].

After oral ingestion, no specific bowel prep is typically required. Imaging is performed at ~28–30 hours to confirm whether the capsule has passed [2,4]. If not seen on X-ray, functional patency is assumed. If visible, retention is suspected—though location (small bowel vs colon) can be difficult to determine on planar images alone [2,3]. If retained, CT can help confirm location and avoid false-positive findings [2,5]. Delayed imaging (e.g., at 72 hours) may further improve diagnostic yield without increasing risk [4]. The capsule begins to dissolve at ~30–33 hours, minimizing the risk of obstruction [1,2].

Conclusion

The patency capsule is a valuable tool to assess small bowel patency and reduce the risk of capsule retention. Radiologists should recognize its appearance and assess for passage at ~30 hours post-ingestion, using adjunct imaging if needed.

References

1. Spada C, Spera G, Riccioni ME, et al. A novel diagnostic tool for detecting functional patency of the small bowel: the Given patency capsule. Endoscopy. 2005;37(9):793–800. https://doi.org/10.1055/s-2005-870246

2. Costigan C, O’Hara FJ, McNamara D. Patency testing improves capsule retention rates but at what cost? Front Med (Lausanne). 2023;10:1046155. https://doi.org/10.3389/fmed.2023.1046155

3. Nemeth A, Kopylov U, Koulaouzidis A, et al. Use of patency capsule in patients with established Crohn’s disease. Endoscopy. 2016;48(4):373–379. https://doi.org/10.1055/s-0034-1393560

4. O’Hara FJ, Costigan C, McNamara D. Extended 72-hour patency capsule protocol improves functional patency rates in high-risk patients undergoing capsule endoscopy. World J Gastrointest Endosc. 2024;16(12):661–667. https://doi.org/10.4253/wjge.v16.i12.661

5. Kim YE, Kim YJ, Kim KO, et al. Patency Capsule and Cross-Sectional Imaging for Predicting Capsule Endoscopy Retention: A Systematic Review and Meta-Analysis. Dig Dis Sci. 2025;70(2):761–773. https://doi.org/10.1007/s10620-024-08835-6

Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone who he has mentored has been accepted into top programs across the country including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

Follow Dr. Rice on Twitter @KevinRiceMD

All posts by Kevin M. Rice, MD