Paintball is a popular recreational sport, especially among teens and young adults, but there's growing concern about its safety.

Injuries most often involve the face and eyes. Pellets can whiz by at velocities of up to 300 feet per second, potentially leading to blindness if safety equipment is not worn correctly.

But now, doctors in England say they have the first known case of a paintball pellet resulting in a different type of injury: liver damage.

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In a report published in The BMJ, doctors describe the case of an 18-year-old who was admitted to a hospital with symptoms that looked like appendicitis. He was taken in for emergency surgery. However, upon closer inspection of his abdomen, the surgeons found extensive internal bleeding coming from the liver.

His abdomen was opened with a larger incision and treatment was applied locally to stop the bleeding.

After the operation, he told doctors he had participated in a paintball game a couple of days prior and was hit in the area, although no bruising appeared.

"This represents the first report of paintball related traumatic liver injury," the doctors wrote in the report.

The patient was allowed to go home, but was readmitted three weeks later after he got an ultrasound and learned that blood had pooled in his liver.

The patient's doctor, Dr. Joshua Luck, a resident surgeon at North Middlesex University Hospital in London and the lead author of the case report, told Live Science that additional testing showed that no further damage had occurred and his body was slowly absorbing the pooled blood.

"In the vast majority of blunt liver injuries, the body is able to heal itself over a period of weeks to months," without the need for further medical assistance, he said.

The doctors noted that organ injuries involving paintballing have been reported three times before, and that those patients had required operations to treat damage to the kidney, penis, and scrotum.

Luck told Live Science that the liver patient is now doing well. The injury happened during his first time playing paintball. "Whether he'll try it again is yet to be decided," Luck said.

The authors concluded that "participants and physicians must both be aware of the possible dangers associated with this sport."