Nasal Polyps
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Direct answer
Bilateral polyps in an adult are usually ethmoidal — pale, oedematous prolapses of allergic or eosinophilic sinus mucosa — and they are managed first medically with intranasal corticosteroids, reserving endoscopic sinus surgery and polypectomy for failure. The antrochoanal polyp of Killian is a different animal: a single, often large polyp arising from the maxillary antrum, escaping through a widened choana into the nasopharynx, classically in children and young adults, and cured only by complete removal. Any unilateral polyp in an adult demands imaging and histology, because inverted papilloma, antrochoanal polyp and tumours coexist in that one finding.
What you must remember
- Ethmoidal polyps: multiple, bilateral, pale grey and semi-translucent, mobile and insensitive; the classic causes are allergy, asthma and chronic rhinosinusitis.
- Antrochoanal (Killian) polyp: single, unilateral, originating in the maxillary antrum, hanging into the nasopharynx; the commonest nasal mass protruding behind the soft palate in a child.
- Samter triad (aspirin-exacerbated respiratory disease): asthma, aspirin sensitivity and nasal polyposis — polyps are notoriously aggressive and recur.
- First-line therapy for bilateral polyps is intranasal corticosteroid spray (fluticasone or mometasone) for at least 8–12 weeks; a short oral steroid course is used as "medical polypectomy" for bulky disease.
- Surgery — endoscopic polypectomy with functional endoscopic sinus surgery — is for failed medical therapy, complete obstruction or suspicion of neoplasia; recurrence is common, and post-operative intranasal steroids are mandatory.
- Cystic fibrosis screening is recommended for bilateral polyps in a child — a Western import, but a tested association.
- Never biopsy a unilateral nasal mass in the clinic before imaging: meningoencephalocele in an infant and juvenile nasopharyngeal angiofibroma in an adolescent boy are contraindications to biopsy, while inverted papilloma needs planned excisional surgery.
Ethmoidal versus antrochoanal: a reasoned comparison
The two polyps differ in almost every dimension, and reasoning through the anatomy explains why. The ethmoidal polyp is the mucosa of the ethmoid labyrinth responding to persistent allergic or eosinophilic inflammation with oedema; the thin ethmoid bone and multiple air cells allow many grapelike prolapses to fill both nasal fossae, so the adult presents with bilateral obstruction, hyposmia, mouth breathing and anterior rhinorrhoea. Because the disease is mucosal and inflammatory, treatment is predominantly medical — steroids shrink the oedema — and surgery, when needed, is a matter of opening drainage and debulking, accepting recurrence with continued steroid spray.
The antrochoanal polyp arises from a single focus, often the mucosa of the maxillary antrum near the natural ostium. It grows as one long pedunculated mass, widens the ostium and choana, and dangles into the nasopharynx, where the patient feels it as a lump behind the soft palate, with unilateral obstruction and sometimes the mass visible behind an elevated palate or hanging below it. Being a single anatomical structure, it does not respond meaningfully to steroids; cutting the pedicle alone guarantees recurrence from the residual antral root, so proper treatment is removal of the entire polyp with its base — by endoscopic endonasal approach, combined where needed with a Caldwell-Luc or canine fossa entry to clear the antrum. Compare the two and the exam answers fall out: number (many versus one), side (bilateral versus unilateral), age (adult versus child and young adult), response (steroids versus surgery) and histology (oedematous allergic mucosa versus mostly cystic degenerate mucosa).
Where students slip
The perennial mistake is treating "a polyp" as one disease. A question stem describing a unilateral mass hanging into the nasopharynx of a 12-year-old answers antrochoanal polyp, not allergic polyposis, and its treatment is complete excision with the antral root, not steroid spray. The second slip is forgetting the biopsy rules: a unilateral polyp in an adult is investigated with CT (which distinguishes a soft-tissue mass from a meningoencephalocele by its connection to the cranial cavity) before any biopsy, and a vascular adolescent tumour is never biopsied as an outpatient. Third, the Samter triad: a stem mentioning aspirin-induced asthma with recurrent polyps expects you to name the triad and to warn against NSAIDs.
Frequently asked questions
Where does an antrochoanal polyp arise from?
The maxillary antrum; it extrudes through the natural or accessory ostium into the nasal cavity and extends through the choana into the nasopharynx.
What is the Samter triad?
Asthma, aspirin sensitivity and nasal polyposis — aspirin-exacerbated respiratory disease — associated with aggressive, recurrent polyps.
What is the first-line treatment of bilateral ethmoidal polyps?
Intranasal corticosteroids for 8–12 weeks, with a short oral steroid course for bulky disease; endoscopic sinus surgery is reserved for failure or complications.
Why must a unilateral nasal mass be imaged before biopsy?
To exclude a meningoencephalocele (biopsy causes CSF leak and meningitis) and a vascular tumour such as juvenile nasopharyngeal angiofibroma, which can bleed catastrophically.
What operation prevents recurrence of an antrochoanal polyp?
Complete removal including the antral base of the polyp — endoscopic excision, often combined with a Caldwell-Luc or canine fossa approach.