He had to leave suddenly to answer the call of nature.

他不得不突然离开去解决下内急。

youdao

He had to leave suddenly to answer the call of nature.

他不得不忽然离开去处理下内急。

youdao

After a long time, she told the doleful story to her friend and said she felt bemused why he would leave suddenly.

很久以后，她把这件痛心的往事讲给朋友听，仍然不明白为什么他会忽然离去。

youdao

The message could not be clearer: The number of requests by French citizens to leave France are suddenly up by 400 to 500 percent.

FORBES: Can The Last Taxpayer Leaving France Please Turn Out The Lights?

For Yu-sung Kim and his family, the decision to leave North Korea came suddenly.

BBC: North Korea: Defectors adjust to life abroad

Also, of course, if you leave the euro, suddenly all debts are denominated in euros, but all income is in relatively less valuable drachmas: you get an instant debt spiral.

BBC: Greece: How do you save an economy from going bust?