Both tonsil and adenoid tissue has the ability to regenerate if it is not completely removed during surgery. Even a very tiny amount of tissue can cause them to grow back. However, this isn't a common occurrence.
There are certain factors that may make your tonsils more likely to grow back, such as if they are removed before the period of time when they would normally be growing has passed. Under normal circumstances, tonsils and adenoids tend to grow at a fairly steady rate until a person is about 8 years of age. At this point, they begin to shrink. Adenoids pretty much disappear by adulthood. Understanding how the tonsils and adenoids normally function and grow may help you determine if your tonsils are likely to grow back or not. For more information, read:
Given the amount of time it takes for tissue to regenerate and a naturally limited growth period, it is unlikely that, should your tonsils grow back, they will ever grow back to their original size.
If you had your adenoids removed at the same time as your tonsils, it is more likely that they will grow back than your tonsils. While I have cared for patients who are having a second adenoidectomy, I have never cared for someone, or even known someone, who has had to have their tonsils removed more than once in a lifetime. If you know someone whose tonsils have grown back, they probably had their tonsils removed many years ago. There was a period of time when the method used to remove the tonsils made it more likely for them to grow back. This method, which involved leaving the outer portion of the tonsils intact in order to reduce pain and decrease the risk of bleeding, is no longer used.
How Can I Tell if My Tonsils Have Grown Back?
If you were under the impression that you would never have another strep infection after having your tonsils removed, you might panic the first time you get a sore throat. While research shows a significant decrease in the number of infections experienced by people who have their tonsils out, you can still get throat infections after having them removed. Just because you get a throat infection does not mean that your tonsils have grown back.
If your tonsils are growing back, you might see bumps where your tonsils used to be, or they may become infected and swollen. This is generally not a concern unless they start causing problems. If you start having chronic throat infections or symptoms of sleep apnea, you should talk to your doctor about the possibility that your tonsils and/or adenoids have grown back and proceed from there.
If you are one of the very few people whose tonsils grow back to a noticeable degree, you can expect your doctor to treat the regrowth in much the same way he or she treated you before your tonsillectomy. If you have a strep infection, you will be given antibiotics. Enlarged tonsils can sometimes be treated using steroids (more research on using steroids to shrink tonsils is needed but preliminary studies have been promising), and as a last resort, surgery. Your doctor probably won't recommend another tonsillectomy unless your tonsils have grown back because they are malignant (you have tonsil cancer), you are having frequent infections, your enlarged tonsils are causing you difficulty in swallowing or breathing, or your sleep apnea has returned.
Medline Plus. Tonsils & Adenoids. Accessed: November 16, 2011 from http://www.nlm.nih.gov/medlineplus/tonsilsandadenoids.html
Pubmed. Effect of tonsillectomy on recurrent sore throat in adults: patients perspectives. Accessed: November 16, 2011 from http://www.ncbi.nlm.nih.gov/pubmed/16917984