HANGZHOU -- Veterinarians are keeping a close eye on a giant panda that received surgery for a serious stomach issue in East China's Zhejiang province.

The four-year-old male panda, Cheng Jiu, remains in a critical condition after having an operation that took a large amount of indigestible food from his stomach on Friday, according to sources with the Hangzhou Zoo where the panda lives.

In late February, the panda's keeper found him eating less and suffering from low energy. He was diagnosed with acute stomach distention and underwent a four-hour operation.

In the 48 hours following the surgery, he suffered reflux multiple times, according to a spokesperson with the Chengdu Research Base of Giant Panda Breeding in Sichuan province. It is unclear whether the panda may have postoperative complications, the spokesperson said.

There are no medical records of pandas with similar conditions and no successful experience to learn from, the spokesperson added.

The giant panda was sent from the Chengdu base to the Hangzhou Zoo in September 2016. Described as an extrovert and smart by his keeper, Cheng Jiu loves apples and tree climbing.