There are 2 parotid and 2 submandibular glands in the body, one on each side. Their primary function is the production of saliva which helps the digestion and ingestion of food.
Reasons for surgery:
Lump in the glands, this is most commonly caused by a benign growth (neoplasm) which usually still needs to be removed as they have a malignant potential. Other much rarer reasons are invasive carcinomas and infections. In the case of submandibular glands, stones which cause blockage and recurrent pain may also be a reason for surgical intervention.
Parotidectomy: this involves removal of the portion of the gland which contains the tumor (usually not the whole gland), the hospital stay is 1-2 nights and return to work is within 1-2 weeks.
Submandibular: this involves removal of the entire gland. The hospital admission is usually 1 night and return to work is within 1-2 weeks.