The medical professionals are bounded by law and medical certifications. That said, the real quality control happens by virtue of the incentive system of free market of millions of patients over many years. Their reputations depend on doing "the right thing" - fix the medical issue, give prevention strategies and keep medical costs as low as possible for the customer.
When a medical professional does "the maybe not completely ethical thing", word spreads and they lose future patients to competition. Business declines. The professional loses standing in the community and current employer would terminate their employment. Future employers need good references. They are socially shunned and have legal proceedings on them.
The doctors there are like chefs in a restaurant. The quality of their work determines their standing and future business. Medical facilities are like restaurants. The quality of their service matters.
One thing to note though is that you want to visit medical professionals in cities and not some rural village doctor. Rural doctors are more likely to have "quality control" issues more as their reputations are not discoverable easily without learning local languages.
