Steven Moss has pretty much seen it all—lodged in people's digestive tracts. As a gastroenterologist at Rhode Island Hospital, he has helped remove batteries, blades and even bed springs from people's esophagi and stomachs. But these patients weren't children. They were adults who had swallowed dangerous objects on purpose.

"Intentional, rather than accidental, swallowing is a poorly recognized and underappreciated problem," Moss said in a prepared statement. Small, smooth objects can generally pass through the body safely, but official guidelines for gastroenterologists recommend removing anything larger than six to 10 centimeters within 24 hours and sharp objects and batteries as soon as possible.

In an analysis of patients at his hospital, Moss and his colleagues found that just 33 people made up the total 305 adult cases where intentionally swallowed objects had to be removed. One habitual swallower was seen 67 times in the course of the eight-year study. The results were published online November 1 in Clinical Gastroenterology and Hepatology.

"The reasons for foreign body ingestion vary," Colin Harrington, a psychiatrist at Rhode Island Hospital and co-author on the new study, said in a prepared statement. "It is one of many forms of self-injurious behavior." Some 79 percent of patients had been diagnosed with at least one psychiatric disorder (outside of their swallowing behavior).

Despite having swallowed some seriously sharp objects, however, none of the patients suffered major complications, and surgery was avoided in all but two cases (by removing the intruding article endoscopically).

Nonetheless, safely retrieving these objects isn't easy—or cheap. With medical, administrative and personnel costs (guards were often required to watch patients to make sure they didn't swallow anything else), the price of these 305 procedures topped $2 million (an average of more than $45,400 per individual patient). Most of the costs (79 percent) were paid out by Medicare or Medicaid, the analysis found.

"Foreign body ingestion is poorly understood, difficult to treat, and consumes considerable physician time and hospital resources," Moss said. "Attention should be focused on investigating how to avoid these preventable and costly episodes."

The five most frequently ingested objects in Moss's study:

Pens (72 cases)

Batteries (28 cases)

Knives (22 cases)

Razor blades (21 cases)

Other metal objects (20 cases)