How Brock Lesnar Beat Diverticulitis And Rebooted his UFC Career

Brock Lesnar and The Undertaker battle it out at the WWE SummerSlam 2015 at Barclays Center of Brooklyn on August 23, 2015 in New York City. Credit: JP Yim / Getty Images

Next month former UFC heavyweight champion and WWE Superstar Brock Lesnar is making a return to the Octagon to fight Mark Hunt at UFC 200 after a long bout with a severe form of diverticulitis, a gastrointestinal condition. Lesnar retired from MMA last year and hasn't made a UFC appearance since 2011, when he lost to Alistair Overeem. After that fight, he returned to the WWE following an eight-year absence. He blames his loss to Overeem on his disease. "In my mind and in my heart, I never lost to a foe. I never lost to an opponent. I lost to diverticulitis. That was my opponent that beat me," he told ESPN.

Lesnar has spent years battling a serious complication of a common condition. Diverticulitis starts as diverticulosis, a disease where a person has developed bulging pockets in the lining of the gastrointestinal tract, usually the colon. These bulges are called diverticula. "It's like these little Swiss cheese outpouchings in the colon," says Dr. Jordan Karlitz, associate professor of medicine in the division of gastroenterology at Tulane University and fellow of the American College of Gastroenterology. If these diverticula become inflamed or infected, it becomes diverticulitis.

According to Cleveland Clinic, about 50 percent of people in Western countries have diverticulosis by age 60. And about 20 percent of all sufferers experience complications, which can include bleeding and diverticulitis.

The treatment for diverticulitis varies. Some people will get better without any intervention, but most people will need to use antibiotics, which may require hospitalization. In rare cases, people undergo surgery to address tears in the bowel or remove part of the bowel. According to the American Association of Family Physicians, about 15 to 30 percent of people who are admitted to a hospital with acute diverticulitis need surgery during that admission.

Lesnar was first diagnosed with diverticulitis in late 2009 and may have been undiagnosed for a year. Karlitz said he wasn't sure whether the physical nature of Lesnar's job could have increased his risk of diverticulitis or made his condition more severe. However, if Lesnar was using any painkillers to address injuries from his work, these could have prolonged his diagnosis. "If somebody's trying to battle through something and they’re just taking pain medicines, that could mask the symptoms," says Karlitz. "[…] Things could potentially get worse without you realizing it."

Reports are mixed about Lesnar's initial treatment. In 2009 he had surgery to repair an area of his colon that was causing fecal matter to leak into his abdominal cavity, according to an interview with MMA website Sherdog. MMA Fighting reported that he used a change in diet to treat his condition rather than turning to surgery. In 2012, after a second bout with this disease, Lesnar underwent surgery to remove a foot of diseased bowel, which offers some insight into the severity of his condition. "If he needed to get operated on, then it was more likely a more serious and complicated bout of diverticulitis," says Karlitz.

No one knows what causes diverticulosis, but one prominent theory is that it's caused by low-fiber diets. This is one dietary characteristic that separates countries with high rates of this condition from those with low rates. However, at least one study found a higher instance of this condition in people with a high-fiber diet. Research has also linked this disease to obesity, lack of exercise, and smoking, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

The history of Lesnar's condition is unclear, but some people battle this disease for extended periods of time, even with treatment. Estimates range, but the Cleveland Clinic says that anywhere from 13 to 33 percent of patients who've had acute diverticulitis may have it again. There is also a form of diverticulitis called atypical smoldering diverticulitis. This occurs when acute diverticulitis is treated with antibiotics but symptoms of the disease continue to linger. Karlitz says this can go on for months or even years.

Whatever the details of his battle with this disease, Lesnar has had a long, traumatic journey with diverticulitis. It has hindered his physical abilities for years and he had major surgery to address it. Many athletes would not come back from a medical issue this severe. Lesnar? Well, he already has plans beyond his UFC 200 fight; he's scheduled to participate in WWE SummerSlam in August.