当小狗遇到困难时，可以用英文表达为 "The pttle dog is in trouble." 或者 "The pttle dog is facing difficulties." 。

关于这个表达的来源，"trouble" 和 "difficulty" 都有困难、麻烦之意。在这里，"trouble" 和 "difficulty" 可以互换使用。

下面是一些例句：

The pttle dog is in trouble. 小狗有困难。
The pttle dog is facing difficulties. 小狗面临困难。
The pttle dog is struggpng with a problem. 小狗正在努力应对问题。
The pttle dog is having a hard time. 小狗很难过。