Killian Polyp of Maxillary Sinus - Clinical Features, Diagnosis, and Treatment

What Is an Antrochoanal Polyp or Killian Polyp?

The Killian polyp, also known as the antrochoanal polyp of the oronasal cavity, is an edematous polyp of the maxillary sinus. This polyp is hypertrophic as the mucosa herniates through the natural or accessory ostium of the maxillary sinus into the nose. The soft palate region is the primary or common location in which to observe the Killian polyp in the oral cavity. This soft mass is rounded in appearance, originating from the nasopharynx and hanging down behind the soft palate into the oropharynx. This polyp has no specific gender preference, affects males and females equally, and is more seen in children and young adults below 18.

What Is the Classification of Killian Polyps?

The Killian polyps are classified into two types based on the size of the polyp -

1. Early Polyp - These polyps have two parts, namely antral and choanal. This early lesion or soft mass, does not project into the nasal region.

2. Late Polyp or Advanced Polyp - In this type, the polyps extend into the nose with three-part divisions - antral, choanal, and nasal.

According to the classification by Strammberger, the antrochoanal polyp or Killian polyp has two components -

• The antral part.

• The choanal part.

The two parts, antral and choanal, are connected by a stalk-like structure that passes through the accessory ostium or the natural ostium. The antral component comprises cystic content in up to 80 % of the cases, while the choanal part tends to have solidified comparatively.

What Are the Clinical Features of the Antrochoanal Polyp or Killian Polyp?

The clinical features of antrochoanal polyp or Killian polyp include -

• Patients mainly complain of nasal obstruction and a dull voice, causing a change in the vocalization with a hyponasal tone of voice. Nasal obstruction is mostly unilateral, and in some cases, it can be bilateral, too. The patient observes or notices this obstruction while reporting to the physician. The obstruction is observed more during exhalation than during inhalation. This can be attributed to the ball valve mechanism that permits air into the nasal cavity unobstructed. However, the patient usually complains of discomfort during expiration because the polyp fills the nasopharynx and eventually blocks the opposite choana part.

• After taking a complete history, the medical practitioner might not find any history related to nasal allergies, rhinitis, or asthma.

• Patients with the Killian polyp have either mucopurulent, mucoid, or thin-to-thick nasal discharge.

• The nasal discharge may vary in consistency and change due to long-standing or chronic maxillary sinus infection.

What Is the Differential Diagnosis of the Antrochoanal or Killian Polyp of the Maxillary Sinus?

• Mucous polyps of nasal origin.

• Inverted papilloma.

• Angiofibroma.

• Sphenochoanal polyp.

• Concha bullosa.

• Meningoencephalocele.

• Neoplasms of the nasal cavity: schwannoma, intranasal glioma, meningioma, hemangiopericytoma.

• Rhinosporidiosis.

How to Diagnose the Antrochoanal or Killian Polyp of the Maxillary Sinus?

The following methods can be used for the diagnosis of Killian polyp -

• Anterior Rhinoscopy - If the growth of the polyp is more anterior-posteriorly, this method can help diagnose this condition as the polyps get large and may extend to the nares anteriorly.

• Probe Test - This test helps detect a movable grayish soft textured mass - polyp. The operator can move the mass up and down, which helps in the initial diagnosis of the polyp. However, in some cases where the polyp is attached more laterally and may not show any attachment to the nasal septum, it may remain undetected.

• Nasal Endoscopy Procedure - This test may be recommended by the physician or the ENT (ear, nose, and throat) specialist in most suspected cases to confirm the diagnosis. In this procedure, the Killian or the Antrochoanal polyp can be observed as a solitary or unilateral mass arising from the middle meatus. The smooth grayish lobular texture of this mass confirms the diagnosis. The infected surface of the Killian polyp at the region of the oropharynx behind the soft palate or sometimes in the nostrils appears pinkish and highly vascular in texture.

• Posterior Rhinoscopy - This procedure is a more accessible and standard diagnostic method to detect polyps hanging behind the soft palate.

• Computed Tomography (CT) scan - The ENT specialist or the otolaryngologist can also recommend a CT scan. In the CT scan, the antrochoanal polyp can be visualized as an opacity within the maxillary sinus that extends into the homogenous nasal cavity.

Radiographic Features:

Plain Radiograph: These have yet to be in use in recent days. In some cases, plain radiographs can be advised. The findings may include

• Opacification on one side of the maxillary sinus.

• Sometimes, nasopharyngeal mass may be observed.

• Most often, bilateral sinus involvement is observed.

Computed Tomography: This is the preferred method for the diagnosis as it gives details about the bony part of the paranasal sinus. The antrochoanal polyps show the following features.

• A mass with a defined mucin density is observed in the maxillary sinus.

• Widening of natural or accessory osteum, which may extend to the nasopharynx.

• No destruction of the bone is seen but the enlargement of the sinus may be observed.

Occasionally, antrochoanal polyps may have high density if they are long-standing or have a fungal infection.

What Is the Management of the Antrochoanal or Killian Polyp of Maxillary Sinus?

There are mainly three major surgical procedures to address or eradicate the Killian polyp of the oronasal region -

1. Endoscopic Sinus Surgery (ESS) - Maxillofacial surgeons and physicians prefer this as mainline surgical treatment. The surgeon enlarges the accessory or natural ostium located within the posterior fontanelles. Some surgeons first prefer to decompress the cystic or the antral component of the polyp by performing the decompression or enteroscopy procedure. In ESS surgery, the stalk of the polyp that originates from the maxillary sinus is eliminated to prevent the recurrence of the lesions.

2. Mini Caldwell Luc Operation - The Caldwell Luc procedure is the mainline or traditional surgical approach for maxillofacial cystic lesions. In this minor procedure, the polyp stalk is eliminated from the origin to prevent any damage to the oral cavity or developing tooth buds. The surgical opening is large, with the central mass of the polyp removed either through the nose or the mouth. The aperture is made by widening it enough to pass an endoscope and forceps in the anterior antral wall of the maxillary sinus.

3. Polypectomy - The canine fossa approach by maxillofacial surgeons is the preferred surgery in children below 10 - 12 years of age by avulsion of the polyp through the oral or the nasal route. This procedure is preferred more than ESS because there is no risk of injury to the developing tooth buds as it is a simple avulsion surgery.

Conclusion:

To conclude, the diagnosis of antrochoanal polyps is challenging and should be confirmed by examination techniques elaborated above and by examining the clinical features of the patient. Surgical approaches aid in good long-term prognosis and prevent the recurrence of this maxillary sinus polyp.