Joe Jonas checked into an emergency room in L.A. while doctors inspected his abs -- for severe stomach pains -- 48 hours after Joe did some late night partying in Chicago.
A rep for Joe confirms he went to the emergency room at Children's Hospital L.A. on Sunday. We're told Joe was only at the hospital briefly ... and it's not clear what was wrong with him.
One potential hint -- on Friday night (into Saturday morning) Joe was out at a Chicago hot spot Board Room Nightclub (above) partying ... and performed the next night in Chi-Town.
Whatever the problem was ... Joe felt good enough to eat out -- we spotted him and his bro Nick leaving Katsuya last night. Sushi after stomach troubles? Risky, Joe.
The Jonas Brothers' show must go on ... but it will go on without a replacement for their special guest act Demi Lovato.
A source connected with the tour tells TMZ, "There are no plans to replace Demi for the remaining six days on the Jonas Brothers Live in Concert tour."
As TMZ first reported, Demi decided to leave the tour and seek help for "physical and emotional issues" at a treatment facility.
Evangelical Christian boy bander Nick Jonas hugged it out with controversial marriage equality opponent and Saddleback Church pastor Rick Warren at Anaheim Stadium on Easter Sunday.
Selena Gomez went shopping in Texas for her "boyfriend" on Tuesday -- and she got the perfect thing for him to play with in his pocket: A watch.
TMZ has learned the teen Disney idol was on the hunt for the perfect timepiece for a special friend -- if you believe the rumors, that friend is Nick Jonas. She picked it up at a jewelry store in the Northpark Mall in Dallas.
We're told she got the watch engraved with the phrase "Check the time ... I love you right now" -- and then personalized the box with a line from a Roy Croft love poem: "I love you, not only for what you are, but for what I am with you."
Good deal ... considering the total bill was only $148.31.