The consequences of surgery often lead to intended benefits, but there is always a cost.
These costs can be in the form of side effects or complications.
Side Effects, are anticipated and quantifiable consequences of surgical therapy
Surgery to the thyroid can entail removal of that organ. The benefit might be to remove a growth, which is beneficial, but a side effect would be the anticipated lack of the hormonal function of that organ. Thus side effects have to be weighed directly in surgical decision making.
Complications are the unintended and variable adverse effects of surgery.
The rates and severity of these can be minimised, but not excluded. Surgical site infections (wound infections) are uncommon in breast and endocrine surgery, but have been documented since time immemorial. Most infections are from the skin, either the patient or the staff, and it is incumbent on all to minimise this risk.
Some complications, such as venous clots (DVT and pulmonary embolism) are rare but the consequences are dramatic. In this we have choices: accept the small risk or take specific action in the form of anticoagulation therapy. The latter has increased bleeding risks, so the choices are yours, but I am happy to give specific advice. Thus we all benefit by concordance.