Can I sue?

Although there are legal channels in place to file a lawsuit for malpractice, most countries outside the US/UK do not have the same mentality and laws  towards negligence. This is one of the primary reasons why treatment overseas is so much cheaper.

If this is an important factor when making your decision then going abroad for treatment may not be the best option for you.
Be sure to seek the advice of a qualified lawyer/solicitor for more comprehensive advice.