Well .. apparently nothing serious. According to the doctors there was no open surgery because of the situation he's in (regarding the upcoming WC) and he will be able to get back to practice in a couple of days - the FIBA World Championship won't be in any danger. So he should still have some sort of trade value
Hedo's quote at the bottom of the article:
The doctors advised me to undergo surgery on my gallbladder so I won't have any problems in the future. So we made an according decision. The doctors wanted to get any suspicions on when some sort of discomfort might occur out of the way. So we decided to put that risk out of the way. I believe I will be able to join the national team in a short while. My return after the surgery will be in 3-4 days. Because of that the doctors wanted to perform this surgery right away.