Patients in Virginia might imagine that anything used during the surgery is removed and accounted for before the site is closed and stitched. However, for thousands of people in the U.S. every year, this is not the case, CNN reports. Roughly a dozen patients each day leave the operating room with a surgical sponge or instrument still inside them. 

Why is this number so high? One of the reasons is that surgical sponges, in particular, are so difficult to keep track of. There may be 50 to 100 of these gauzy pads used per surgery, and these make up about 70 percent of all retained objects. Sponges are also often difficult to detect with imaging immediately after the operation, where a needle or scissors would be glaringly obvious on an x-ray. Sponges are most likely to be left behind after an abdominal surgery, although there are documented cases of retained sponges after nasal and brain surgeries, as well as other procedures.

There may be many more sponges left behind than studies have indicated because a patient may not experience symptoms for years. Even then, the symptoms may mirror other medical conditions, resulting in a misdiagnosis. When sponges are not discovered, they often drift away from the surgical site and become entangled or enmeshed in organs, causing serious internal damage. 

The National Institutes of Health notes that often, the sponges cause inflammatory reactions, infections and abscesses. In almost every case, a patient will need at least one corrective surgery, and the outlook is best when the object is discovered and removed within two weeks of the initial procedure.