Paranasal sinuses rule 3 :Causes of sinus opacification

Causes are

1-Sinusitis.

2-Mucocele.

3-Pyocele.

5-Polyposis

This include

-Sinonasal polyposis.

-Antrochoanal polyp.

-Inverted papilloma.

6-Neoplasm including carcinoma or metastases.

7-Retention cyst.

1-Sinusitis:

It could be acute, chronic or fungal sinusitis.

Acute sinusitis can be diagnosed by presence of air fluid level inside sinus(fluid level appears straight or concave superiorly while retention cyst or polyp is convex superiorly).

Chronic sinusitis suggested by presence of mucosal thickening.

Fungal sinusitis characterized by aggressiveness with marked increased density and calcification with CT imaging and marked hypo intensity in T2 MRI imaging.

 Acute sinusitis with mucosal thickening and fluid level.

 Fluid level in acute sinusitis.

Chronic sinusitis with mucosal thickening

MRI T2 image shows marked low intensity at left maxillary and sphenoid sinuses due to fungal sinusitis(characteristic appearance).

2-Mucocele:

Characterized by sinus opacification with sinus enlargement, much wall thinning with less bone destruction and no enhancement.

3-Pyocele:

Characterized the same as hydrocele with ring enhancement after contrast injection.

Pyocele of the left middle turbinate.

4-Polyposis disease:

This include the following

-Sino nasal polyposis:

Which is characterized by diffuse involvement of sinuses and nasal cavity with soft tissue mass causing enlargement with thinning of bone boundaries with little bone destruction and widening of the osteo meatal complex.

-Antrochoanal polyp(ACP):

Arises from maxillary sinus  and extending to the nasal cavity but sparing ethmoidal sinuses.

-Inverted papilloma(IP):

Arise from nasal cavity and extends to both ethmoidal sinuses and maxillary sinuses.

Difference between                        ACP                                      IP

Site of largest component         maxillary sinus                      nasal cavity

Ethmoidal sinus affection          not affected                          affected

 Sino-nasal polyposis.

Inverted papilloma

Antrochoanal polyp

5-Sinus neoplasm:

-This include both primary as carcinoma and secondaries.

-There are less sinus enlargement, less bone thinning with much wall destruction giving heterogenous or homogenous enhancement.

 Sinus neoplasm.

6-Retention cyst:

-Due to accumulation of secretion under mucosa of the sinus.

-Results in a lesion adherent to the wall of the sinus with rounded edge simulating a polyp.

-Retention cyst is much more prominent in the clinical practice rather the polyp.

-To differentiate between both, look to the nasal cavity, if you do not see a polyp inside it, so the one seen in the sinus is a retention cyst, but if you find a polyp in the nasal cavity, so both are polyps. 

Retention cyst.