The adenoids are a patch of lymphoid tissue situated in the upper throat, behind the nasal passages in the nasopharynx. As part of the immune system, they trap and neutralize bacteria and viruses breathed in through the nose and mouth. This tissue produces antibodies and plays a role in immunological memory, particularly in young children. Unlike the tonsils, the adenoids are not visible by looking into the mouth.
Adenoid Development and Age-Related Changes
The size of the adenoids changes significantly over childhood. They are present at birth but grow, reaching peak size during the preschool and early school years, typically between the ages of three and seven. This growth phase corresponds with the period when children are actively building immunity through exposure to various germs.
After this peak, the adenoids naturally begin a process of atrophy, or shrinkage, as the body develops other methods to combat infections. By adolescence, the adenoids are often significantly smaller and may almost completely disappear by adulthood.
An absolute measurement is less informative than the adenoids’ size relative to the surrounding airway space. While the median adenoid depth remains consistent (about 14 to 15 millimeters) between ages one and twelve, the depth of the nasopharynx increases with age. Thus, the same absolute size occupies a smaller proportion of the airway in an older child.
Clinical Assessment of Adenoid Size
Assessing pathologically enlarged adenoids requires evaluating the degree of airway obstruction. Since adenoids are located high in the nasopharynx, they cannot be seen during a routine throat examination. Two primary methods evaluate their size and impact.
One common non-invasive technique is the lateral neck X-ray. Radiologists calculate the adenoid-to-nasopharyngeal ratio (AN ratio), comparing the depth of the adenoid tissue to the nasopharyngeal airway. An AN ratio greater than 0.80 often suggests significant enlargement.
The most precise method is nasal endoscopy, which involves inserting a thin, flexible tube with a camera through the nose. This allows for direct visualization of the adenoid tissue and surrounding structures, including the Eustachian tube openings. Endoscopy enables providers to measure size and directly observe the degree of nasal obstruction.
Symptoms and Functional Impact of Enlargement
Pathologically enlarged adenoids, a condition known as adenoid hypertrophy, obstruct the upper airway, leading to several distinct health issues. Since the nasal passage is blocked, children are forced into chronic mouth breathing, especially at night. This breathing pattern can result in a dry mouth, cracked lips, and sometimes a hyponasal voice quality due to poor nasal resonance.
A significant consequence is obstructive sleep-disordered breathing, manifesting as loud snoring or, in severe cases, obstructive sleep apnea (OSA). During OSA, the airway completely collapses for short periods, causing the child to stop breathing repeatedly throughout the night. This disrupted sleep can cause daytime fatigue, behavioral issues, and potentially affect development.
Enlarged adenoids often cause recurrent ear problems because of their proximity to the Eustachian tubes, which connect the middle ear to the nasopharynx. Swollen adenoids can block these tubes, preventing proper ventilation and drainage from the middle ear. This obstruction leads to fluid accumulation (otitis media with effusion), which can cause temporary hearing loss.
Persistent mouth breathing due to severe, long-term obstruction may also contribute to changes in craniofacial development, sometimes referred to as “adenoid facies.” These characteristics include a high-arched palate, a continuously open mouth, and a flattened mid-face. The presence of these functional impacts, rather than absolute size alone, dictates the need for medical intervention.