antrochoanal polyps ( acps ) are benign lesions arising from the edematous mucosa of the maxillary sinus and extending into the choana .
acps constitute 4%6% of all nasal polyps . despite nasal polyposis , acps are typically unilateral .
however , most of the published studies have been unanimous about preponderance of males and also its peak in early decades of life .
chronic sinusitis and allergic rhinitis seem to play a major role in establishing the acp .
one of the suggested etiological theories for acp described that inflammatory - related closure of osteomeatal complex and increase of pressure in maxillary sinus force mucous retention cysts to herniate into the nasal cavity .
considering this theory , anatomic variations such as septal deviation , hypertrophic turbinate , and concha bullosa also pave the way for increasing the pressure difference between the middle meatus and the maxillary sinus . in this study , we examine this theory by comparing the coincidence of anatomic variation in patients with acp with normal population .
between march 2014 and august 2015 , among patients referred to radiology department , kashani and alzahra hospitals ( isfahan university of medical sciences , isfahan ) by their clinicians for standard computed tomography ( ct ) scan of paranasal sinuses patients with the imaging diagnosis of acp were enrolled to the study , consecutively .
seventy - eight patients with no evidence of polyposis were randomly selected and matched by sex and age with acp cases .
septal deviation , unilateral or bilateral concha bullosa , and retention cyst in contralateral maxillary sinus were evaluated in both groups .
data of both groups entered to ( spss version 22 , ibm corporation , somers , ny , usa ) .
of the 17 patients with acp , 10 ( 58.8% ) were males and 7 ( 41.2% ) were females .
ages ranged from 18 to 67 years with a mean of 38.11  11.06 years .
of the 78 patients in control group , 38 ( 48.7% ) were males and 40 ( 51.3% ) were females .
ages ranged from 20 to 66 years with a mean of 35.08  10.45 years .
twenty - nine patients ( 37.2% ) had septal deviation , 6 ( 7.7% ) had concha bullosa , 7 ( 8.9% ) had retention cyst , and 1 ( 1.2% ) had hypertrophic turbinate .
whitney u - test showed the higher coexistence of septal deviation in patients with acp in comparison with control group , significantly ( p < 0.001 ) .
however , there was no significant difference in incidence of concha bullosa between two groups .
chronic sinusitis which has been introduced as an important factor in the etiology of acp , instead could be the result of an obstruction of the maxillary sinus ostium caused by acp .
while some studies have found significant association between acp and allergy , others fail to detect this association .
role of anatomic variations of paranasal sinuses is another state of debate . in a large series of patients with acp reported by frosini et al . , the only significant correlating factor found in the patients was the anatomical variation . in their series , rate of septal deviation ( 55% ) ,
inferior turbinate hypertrophy , and concha bullosa were 55% , 21% , and 7% , respectively .
they found that 32.3% of their cases had a contralateral mucous retention cyst . in our series , 37.2% had septal deviation , 7.7% had concha bullosa , 8.9% had retention cyst , and 1.2% had hypertrophic turbinate .
while some authors consider etiologic role for some of the anatomic variations in establishment of acp , the others claim these variations are secondary to the presence of acp .
diagnosis is based on physical examination , includes anterior rhinoscopy and nasofibroscope and ct scan .
ct scan is helpful not only in the diagnosis of acp but also in choosing the appropriate surgical approach as it offers valuable information about the boundaries of each polyp . magnetic resonance imaging has been also used in acp .
on t1-weighted images , acp is intermediate to low signal ; and on t2-weighted images , it is heterogeneously high .
the major imaging differential diagnoses for acp are retention cysts , acute sinusitis with prolapsed mucosa , inverted papilloma , maxillary sinus mucocele , sinonasal organized hematoma , nasoethmoidal encephalocoele , esthesioneuroblastoma , and juvenile nasopharyngeal angiofibroma .
this study showed that septal deviation is an anatomic variation which is significantly concomitant with acp .
larger studies are needed to show the role of other anatomic variations in patients with acp .
all authors contributed in the conception of the work , conducting the study , revising the draft , approval of the final version of the manuscript , and agreed for all aspects of the work .
 background : this study was designed to determine the prevalence of concomitant anatomic variation of paranasal sinuses in patients with antrochoanal polyp ( acp).materials and methods : among patients referred by their clinicians for standard computed tomography scan of paranasal sinuses septal deviation , concha bullosa , and retention cyst were evaluated in both patients with acp as well as in a control group.results:of the 17 patients with acp , fifteen patients ( 88.2% ) had septal deviation and two patients ( 11.8% ) had concha bullosa . 
 none of the patients with acp had retention cyst or hypertrophic turbinate . 
 of the 78 patients in control group , twenty - nine ( 37.2% ) had septal deviation , six ( 7.7% ) had concha bullosa , seven ( 8.9% ) had retention cyst , and one ( 1.2% ) had hypertrophic turbinate . 
 septal deviation in patients with acp has higher incidence ( p < 0.001).conclusion : this study showed that septal deviation is an anatomic variation which is significantly concomitant with acp . 
 larger studies are needed to show the role of other anatomic variations in patients with acp . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION
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