The document defines adenoiditis as an infection of the adenoids, lymphatic tissue located in the nasopharynx, which often accompanies acute tonsillitis. Adenoiditis can be caused by bacteria like GABHS or viruses such as Epstein-Barr. Clinical features include enlarged adenoids, mouth breathing, ear ache, foul breath, nasal obstruction, colds, and impaired voice. Diagnosis involves a history and physical exam, and possibly audiometry for recurrent cases. Management consists of antibiotics, antimicrobials, and potentially adenoidectomy.