Thursday afternoon the UFC used a quickly convened conference call to announce that this latest flareup of the disease will keep Lesnar out of the octagon indefinitely, forcing him out of a scheduled June 11 showdown in Vancouver with fellow contender Junior Dos Santos.
The winner of that bout was to have faced Cain Velasquez, who knocked Lesnar out to claim the UFC heavyweight crown last October. And while Lesnar's disappointed at the missed opportunity he says the return of the intestinal disorder has forced him to prioritize.
"I'm choked up about it (but)there's nothing I can do," said Lesnar, a former WWE star who joined the UFC in 2008. "There isn't a fight in the world that's more important than my health."
In November 2009 a severe case of diverticulosis felled Lesnar while on a hunting trip in Manitoba, leading to an experience with the Canadian health care system that left the then-heavyweight champion less than impressed.
A month later UFC president Dana White still wasn't sure if the disease would allow Lesnar to compete again, but the turn of the year 2010 also brought a turn in Lesnar's health. By the end of January he announced that medication plus a new, healthier diet had chased the disease into remission, and June he had vanquished interim champ Shane Carwin to reclaim the UFC's heavyweight belt.
The path back to that title was supposed to go through Dos Santos, a hard-hitting Brazilian who hasn't lost since 2007. Earlier this year the UFC chose the two men to coach opposing teams of aspiring fighters on the SpikeTV reality show The Ultimate Fighter, with all sub-plots leading to their clash at UFC 131 in Vancouver.
But three weeks ago Lesnar felt a familiar pain in his abdomen.
The sheer stress of three-a-day workouts had allowed the infection, which never fully leaves a patient's system, to regain a foothold. Lesnar responded by scaling back his training while taking antibiotics, but after three weeks of cutting corners he realized he'd never be able to prepare properly while still fighting the infection.
"It didn't allow me to train to my full capabilities," says Lesnar, who won the UFC title in just his third pro bout. "It just drains my whole body down"
When Lesnar decided to pull out of the fight the UFC summoned Carwin to replace him against Dos Santos.
But the next steps for the fighter aren't so clear.
He's considering surgery, but hasn't yet established a timeline to decide whether to undergo it. In the meantime he'll consult with doctors at the Mayo clinic over the best way to subdue the stubborn infection.
"There's a solution to every problem," he says. "I've just got to find the right solution to this problem"
But despite the uncertainty over surgery, Lesnar is sure he will return to the Octagon eventually.
"I'm looking for the light at the end of the tunnel here," he said. "I'm sick and tired of being sick and tired. We've got to find a solution to this."