TOKYO, Japan (CNN) -- Japan's outgoing Prime Minister Shinzo Abe was hospitalized for gastrointestinal inflammation caused by exhaustion and stress Thursday. His hospitalization comes a day after announcing his resignation following a sound electoral beating and the resignations of several government ministers.
Prime Mininster Shinzo Abe listens to questions during a press conference on Wednesday.
Toshifumi Hibi, a doctor at Keio University Hospital, told reporters the 52-year-old prime minister would be hospitalized for at least three to four days to receive treatment, depending upon how his condition progresses.
"He is suffering from extreme exhaustion," Hibi said, adding Abe has lost about 11 pounds (5 kg) in recent months.
Symptoms of gastroenteritis -- or gastrointestinal inflammation -- include vomiting, diarrhea, headache, fever and abdominal cramps, according to a Web site for the Centers for Disease Control and Prevention in Atlanta.
Meanwhile, Japanese political leaders have been working to find a replacement for Abe, after he announced on Wednesday that he was "having an adverse effect" on Japan's ability to contribute to the U.S.-led war on terrorism.
The ruling Liberal Democratic Party (LDP) is expected to announce a replacement for Abe -- who led Japan for a year -- as party leader next week.
A meeting between members of the Diet, Japan's parliament, took place Thursday but Abe could not attend, Hibi said, due to his health condition.
The prime minister on Wednesday said Japan should try to have a new leader "as soon as possible." Former Foreign Minister Taro Aso, who serves as secretary-general of the LDP, is the early front-runner to replace him.
One possible candidate, Japanese lawmaker Yasuo Fukuda, told reporters, "I am still in shock" at Abe's resignation announcement.
There have been very few bright days for Abe and his party -- which has dominated Japanese politics from the end of World War II -- since they lost control of the upper house of Japan's parliament to the opposition in July's elections. Abe described those results as "very bad."
"I have decided that it is time to take a new approach -- time for a new face," he said. "And perhaps this is something that needs to be done under a new prime minister."
Abe had threatened to resign earlier this week if the Diet did not authorize Japanese ships to provide naval support to the coalition battling al Qaeda and Taliban fighters in Afghanistan. Japan's post-World War II constitution bars its armed forces from taking part in combat missions for anything but self-defense.
There has been no vote yet -- but with his approval ratings hovering around 30 percent, Abe said he may not be the right person to guide that legislation through parliament.
"I think it is time I took the appropriate measures to make a breakthrough, and that is the decision I have made," he said.
Since reshuffling his cabinet two weeks ago, Abe has lost four party members to scandals: his new agricultural minister -- the second in a month -- a deputy foreign minister, a mid-ranking parliamentarian and a newly elected member of Japan's upper house have all resigned over allegations of financial or electoral misconduct.
A fifth minister committed suicide in May, hours before he was scheduled to appear before parliament to answer to corruption charges. And the only popular member of his new cabinet, Yoichi Masuzoe, is stuck with the unenviable and potentially embarrassing task of chasing down social-welfare agency officials suspected of stealing from the nation's pension fund.
Meanwhile, bilateral talks with North Korea on the abduction of Japanese citizens -- an item high on Abe's agenda -- have fizzled.
It wasn't always like this for Abe. The leader of the world's second-largest economy seemed to have it all when he took the helm from Junichiro Koizumi almost a year ago, drawing a 60 percent approval rating and the honor of being Japan's youngest leader since World War II.
But that was before a slew of gaffes and scandals. His health minister referred to women as "birth-giving machines," and his defense minister stepped down after hinting that the atomic bombs dropped on Hiroshima and Nagasaki may have been justified. E-mail to a friend
CNN's Junko Ogura contributed to this report.