"Woke up at 3am with a severe and a sharp pain in my abdomen. Knew something wasn't right," Derek, 34, wrote on Instagram.
"Turned out it was appendicitis and had surgery to remove my appendix straight away."
Derek, however, appeared to be in good spirits after the surgery, as he was up and about in his hospital room.
Derek even posted a short video of himself trying to dance in his hospital gown shortly after the medical procedure.
"This is me immediately after, still a little(a lot) medicated, giving @hayley.erbert a (sexy) little dance," Derek wrote alongside the video, referencing his girlfriend and Dancing with the Stars Troupe member Hayley Erbert.
"Me: Is this doing it for you babe? Hayley: So hot. Thank you for lying to me babe ;)."
Hayley was apparently the one who filmed Derek attempting to bust a move in the hospital, so she must have stayed by his side throughout his medical scare.
Hayley even posted a photo of Derek knocked out in his hospital bed in her Instagram Stories, according to The Blast.
Hayley reportedly inserted cat gifs onto the sleeping dancer to strategically cover some areas of his body.
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"Wherever we go, there's a partayyy," Hayley reportedly wrote alongside the image.
Comments from concerned friends and fans poured in on Derek's Instagram account, including a message from Dancing with the Stars pro Emma Slater.
"Ooooo dude hope you're ok, take care of yourself," Emma wrote.
Derek and Hayley, who also competed on So You Think You Can Dance, have been linked for over three years, but they kept their romance fairly private in the beginning stages.
Derek and Hayley recently documented their trip to South Korea in which Derek gushed on Instagram they met "great people," enjoyed "great food," and had an "amazing experience" together. Not long before that, the couple went to Paris, France.
In recent months, the couple hasn't been shy to share their love for one another on social media.
Prior to starring on World of Dance, Derek competed on 17 seasons of Dancing with the Stars, with his last appearance being on Season 23 with his celebrity partner Marilu Henner. Derek won more mirrorball trophies than any other pro on the show, with a total of six wins.
Dancing with the Stars is currently airing its 28th season on ABC.