A patency capsule is administered as a test of intestinal luminal patency, before a capsule endoscope is swallowed. The patency capsule should be passed in the feces within 30 hours, indicating that there is no significant small bowel stricture. This time is clearly affected by colonic transit time, and if the capsule is not passed or not thought to have been passed, abdominal radiography may be used to identify it. They contain an RFID chip which may be detected via an external RFID scanner.

They are composed of barium to enable detection using radiography, and lactose that can dissolve. They are designed to start dissolving 30 hours following ingestion. Occasionally however, they may be detected beyond 30 hours as is the case here.

Retention of a capsule endoscope, as they are not soluble, may lead to surgical intervention; therefore successful passage of a patency capsule is considered an important precursor to administering a capsule endoscope.

A small bowel stricture was identified in this case on subsequent imaging (not shown here).