Mastoidectomy is a risky surgery?

Complications may occur during any surgery. Ophthalmologic surgery, however, is usually very safe.

No. It is a fairly straightforward procedure. The risks of a cholecystectomy are essentially the risks of anesthesia.

Yes it does carry a high risk

The procedure usually takes between two and three hours. It is occasionally performed on an outpatient basis in adults but usually involves hospitalization

That depends on the actual hemorrhoid and how long you have had it. The doctor should be able to discuss the procedure with you before surgery and tell you all of the risks