Nasal mucosa, particularly in the region of middle meatus becomes swollen due to collection of extracellular fluid. This extracellular fluid collection causes polyp formation and protrusion into the nasal cavity or sinuses. Polyps which are sessile in the beginning become pedunculated due to gravity.In people with nasal polyps due to aspirin or NSAID sensitivity, the underlying mechanism is due to disorders in the metabolism of arachidonic acid. Exposure to cycloxygenase inhibitors such as aspirin and NSAIDs leads to shunting of products through the lipoxygenase pathway leading to an increased production of products that cause inflammation. In the airway, these inflammatory products lead to symptoms of asthma such as wheezing as well as nasal polyp formation. Diagnosis
Nasal polyps can be seen on physical examination inside of the nose and are often detected during the evaluation of symptoms. On examination, a polyp will appear as a visible mass in the nostril. Some polyps may be seen with anterior rhinoscopy (looking in the nose with a nasal speculum and a light), but frequently, they are farther back in the nose and must be seen by nasal endoscopy. Nasal endoscopy involves passing a small, rigid camera with a light source into the nose. An image is projected onto a screen in the office so the doctor can examine the nasal passages and sinuses in greater detail.
The procedure is not generally painful, but the person can be given a spray decongestant and local anesthetic to minimize discomfort.Attempts have been made to develop scoring systems to determine the severity of nasal polyps. Proposed staging systems take into account the extent of polyps seen on endoscopic exam and the number of sinuses affected on CT imaging. This staging system is only partially validated, but in the future, may be useful for communicating the severity of disease, assessing treatment response, and planning treatment. Types
There are two primary types of nasal polyps: ethmoidal and antrochoanal. Ethmoidal polyps arise from the ethmoid sinuses and extend through the middle meatus into the nasal cavity. Antrochoanal polyps usually arise in the maxillary sinus and extend into the nasopharynx and represent only 4–6% of all nasal polyps.However, antrochoanal polyps are more common in children comprising one-third of all polyps in this population. Ethmoidal polyps are usually smaller and multiple while antrochoanal polyps are usually single and larger. CT scan
CT scan can show the full extent of the polyp, which may not be fully appreciated with physical examination alone. Imaging is also required for planning surgical treatment. On a CT scan, a nasal polyp generally has an attenuation of 10–18 Hounsfield units, which is similar to that of mucus. Nasal polyps may have calcification. Histology
On histologic examination, nasal polyps consist of hyperplastic edematous (excess fluid) connective tissue with some seromucous glands and cells representing inflammation (mostly neutrophils and eosinophils). Polyps have virtually no neurons.