The adenoid, also known as a pharyngeal tonsil or nasopharyngeal tonsil, is a mass of lymphatic tissue situated posterior to the nasal cavity, in the roof of the nasopharynx, where the nose blends into the throat. Normally, in children, it forms a soft mound in the roof and posterior wall of the nasopharynx, just above and behind the uvula.
An enlarged adenoid, or adenoid hypertrophy, can become nearly the size of a ping pong ball and completely block airflow through the nasal passages. Even if the enlarged adenoid is not substantial enough to physically block the back of the nose, it can obstruct airflow enough so that breathing through the nose requires an uncomfortable amount of work, and inhalation occurs instead through an open mouth. The enlarged adenoid can also obstruct the nasal airway enough to affect the voice without actually stopping nasal airflow altogether.
Enlargement of the adenoid, especially in children, causes an atypical appearance of the face, often referred to as adenoid faces. Features of adenoid faces include mouth breathing, an elongated face, prominent incisors, hypoplasticmaxilla, short upper lip, elevated nostrils, and a high arched palate. George Catlin, in his humorous and instructive book Breath of Life, published in 1861, illustrates adenoid faces in many engravings and advocates nose-breathing.
Surgical removal of the adenoid is a procedure called adenoidectomy. Adenoid infection may cause symptoms such as excessive mucus production, which can be treated by its removal. Studies have shown that adenoid regrowth occurs in as many as 20% of the cases after removal. Carried out through the mouth under a general anaesthetic (or less commonly a topical), adenoidectomy involves the adenoid being curetted, cauterised, lasered, or otherwise ablated.