Paintball has been growing in popularity over the past few years, allowing groups of friends to split into teams and shoot one another or go against another group of strangers.

While the game is fun, it's certainly not harmless. Paintball requires players to wear helmets and other pieces of protective gear since the pellets can cause bodily harm on unexposed areas. Up until now, it was believed that the worst someone could receive were bruises here and there, but the story of one teenager in England reveals that injuries received in paintball can be far worse.

In a report published in the May 5 issue of the journal BMJ Case Reports, a team of doctors detailed the tale of an 18-year-old who wound up requiring surgery after being struck in the abdomen during a paintball game.

It all began in August 2015 when the teen went to the emergency room complaining about abdominal pain and a low-grade fever, said Dr. Joshua Luck, a surgeon at North Middlesex University Hospital in London, who treated the patient and is the lead author of the case report.

The teen didn't tell doctors that he had played paintball two days prior (though that wouldn't have changed much for the doctors), and based on his symptoms, they diagnosed him with appendicitis and scheduled him to have emergency surgery.

However, instead of seeing the usual damage in the appendix when the operation began, doctors actually saw blood coming from the liver. Due to the blood in the abdominal cavity being so unexpected, they assumed that they made a mistake themselves and injured a blood vessel in the process.

The doctors eventually stopped the bleeding and finished the operation, and it wasn't until then that they learned their patient had been playing paintball two days before and was hit twice in the abdomen. The revelation was quite a shock for the doctors, though it wasn't the first injury to be incurred from paintball. It was the fourth that resulted in organ damage and the very first that involved the liver.

Even more shocking for them was the fact that there were no bruises on his skin near the liver, though it has been noted that seemingly innocuous events can cause internal injuries.

Two days after the operation, the man was allowed to leave the hospital, but he returned three weeks later to reveal that he had undergone an ultrasound, which showed that there was still pooled blood in the liver. This revelation raised concerns that the original injury was still bleeding, or that he might have reinjured his liver. However, doctors determined that the body was indeed reabsorbing the pooled blood, albeit at a slower rate than usual.

"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," Luck said.

The patient is okay, but the whole situation raises questions about how dangerous paintball is. Paintball guns vary greatly in size and power, with pellets ranging from 0.4 to 0.7 caliber and velocities topping 200 mph when fired.

"Participants and physicians must both be aware of the possible dangers associated with this recreational sport," Luck said.

"This case report adds to the growing literature on paintball-related injuries and shows that pellets with muzzle velocities of 100 to 300 feet per second are potentially harmful to ocular structures and also to the intra-abdominal solid organs."

However, Andrew Naylor of UK Paintball - Britain's biggest paintballing company - says that the reports of injuries have been exaggerated.

"Paintball," Naylor said, "like any other sport, does carry a small element of risk to it. This is why there is such an importance of using the correct equipment, and making sure that the marshals are correctly trained to the proper standards.

"So, as long as you stick to the guidelines set out by governing bodies such as the UK Paintball Sport Federation, the likelihood of an injury is dramatically decreased."