Despite the importance due to its high occurrence rate among ORL patients, only a very limited number of studies have been conducted for the explanation of the origin of nasal polyps especially developed inside the maxillary sinuses. In the present study, a virtual polypectomy was performed for the CT data of the patient who suffered polyps developed in the maxillary sinus in order to understand the physiological cause for polyps in a situation where a magnitude of the velocity is quite low such as in the nasal sinuses. Our steady simulation suggested that there is a high correlation between the location of flow separation and the development of polypoid. At present, it is not clear how the existence of flow separation provides
physiological irritation to the nasal epithelium and our future study with unsteady simulation is expected to yield more precise information.