accessory fissures in the lungs are common congenital variations , which occur due to lack of obliteration of fissures separating individual bronchopulmonary segments during the development . presence of accessory fissures should be documented in the radiological report as they affect the surgical planning , especially in pulmonary malignancies .
we report a case of non - azygos accessory fissure between the apical and the anterior segments of the right upper lobe , associated with inferior and superior accessory fissures in the right lower lobe , which was detected in the ct - portion of positron emission tomography - computed tomography ( pet - ct ) .
a 40-year - old woman with a known diagnosis of extra - nodal ( bone marrow , spleen , and pleural fluid ) stage iv diffuse large b - cell lymphoma was referred for baseline pet - ct scan before the initiation of treatment .
pet - ct scan showed diffuse increased fluorodeoxyglucose uptake in the marrow consistent with known marrow involvement by lymphoma , in addition to splenomegaly .
incidentally noted in the ct portion of the pet - ct was an accessory fissure in the right upper lobe .
the dedicated ct scan of the chest demonstrated the fissure better than the ct portion of the pet - ct , due to lack of breathing artifact and the accentuation caused by the pleural effusion .
the accessory fissure was between the apical and anterior segments of the right upper lobe [ figures 1 and 2 ] .
the contrast - enhanced ct scan showed normal location and course of the azygos vein [ figure 1 ] .
in addition , the patient also had inferior and superior accessory fissures in the right lower lobe [ figures 3 and 4 ] .
( a ) axial ct image shows the non - azygos accessory fissure in the right upper lobe ( arrows ) , ( b ) contrast - enhanced axial ct scan shows the normal location of the azygos vein .
( a ) axial , ( b ) coronal reformatted and ( c ) sagittal reformatted images show the non - azygos accessory fissure in the right upper lobe ( arrows ) , between the apical and anterior segments .
right pleural effusion is seen extending into the posterior portion of the major fissure in the sagittal reformatted image .
( a ) axial , ( b ) coronal reformatted and ( c ) sagittal reformatted images show the inferior accessory fissure in the right lower lobe ( double arrows ) .
extension of pleuraleffusion in to major fissure ( long arrow ) , and superior accessory fissure ( short thick arrow ) is revealed in the sagittal reformatted image .
( a ) axial , ( b ) coronal reformatted and ( c ) sagittal reformatted images of the follow - up ct scan after the resolution of pleural effusion show the superior accessory fissure in the right lower lobe ( arrows ) .
accessory fissures generally occur between bronchopulmonary segments , as a cleft of varying depth lined by visceral pleura .
they are more common in fetal and neonatal lung specimens than in adult lung specimens . during the development
, the lung tissue grows as multiple bronchopulmonary buds with fissures separating individual bronchopulmonary segments .
later , the fissures separating individual bronchopulmonary segments become obliterated except the major ( oblique ) and minor ( horizontal ) fissures in a fully developed lung .
the accessory fissures are not well demonstrated in conventional ct examinations , due to thick slices and orientation of the fissures relative to the scan plane .
high - resolution computed tomography ( hrct ) demonstrates the accessory fissures at a higher frequency compared to conventional ct scan with thicker sections due to better spatial resolution as a result of narrow collimation and high - spatial resolution reconstruction algorithm .
multi - detector computed tomography ( mdct ) has even higher sensitivity for detection of accessory fissures , with incidence of accessory fissures being similar to anatomical studies due to further thin cuts , faster speed , and volumetric acquisition .
common accessory fissures include the inferior accessory fissure ( demarcates the medial basal segment of the lower lobe ) , left minor fissure ( demarcates the lingula ) , and superior accessory fissure ( demarcates the superior segment of lower lobes ) .
less common accessory fissures include the fissures between medial and lateral segments of middle lobe , between superior and inferior segments of lingula , between anterobasal and laterobasal segments of lower lobes , between apicoposterior and anterior segments of left upper lobe , and azygos fissure ( resulting from the abnormal course of the azygos vein ) . in a retrospective study of 150 cases by cronin et al . ,
using mdct , the incidence of accessory fissures was found to be : superior accessory fissure 6% , inferior accessory fissure 12.7% , left minor fissure 16% , fissure between medial and lateral segments of middle lobe 5.3% , fissure between superior and inferior segment of lingula 2.7% , fissure between anterobasal and laterobasal segment 3.3% , and azygos fissure 0.7% .
our patient had an accessory fissure between the apical and the anterior segments of the right upper lobe .
accessory fissure in the right upper lobe other than due to the anomalous course of azygos vein is very rare .
gowrinath et al . , reported a case of non - azygos accessory fissure between the apical and the posterior segments of right upper lobe .
tzn et al . , described double accessory fissures in the upper lobe of the right lung which are likely variation of an azygos fissure ( double azygos fissures ) , since their configurations and locations were similar .
to the best of our knowledge , non - azygos accessory fissure between the apical and the anterior segments of right upper lobe , associated with superior and inferior accessory fissures of the right lower lobe has not been described in the literature .
the pleural fissures can act as an anatomic barrier to the spread of inflammatory or neoplastic disease .
accessory fissure may cause diagnostic confusion as it can limit the spread of disease within the lung , mimicking atelectasis , scar , mass , or loculated pleural effusion in radiographs .
although the accessory fissures are incidental findings detected on radiographs or ct scan , they are important as they present an anatomic barrier to the spread of inflammatory or neoplastic disease as well as mimic lesions .
recognition of the accessory fissures provides additional information for segmental localization of pulmonary lesions , as well as help in surgical planning .
 accessory fissures in the lungs are common congenital variations , usually detected as incidental findings in radiographs or ct scan . 
 accessory fissures can act as an anatomic barrier to the spread of inflammatory or neoplastic disease , as well as due to the variant anatomy , mimic lesions . 
 it is important to recognize the presence of accessory fissures , as they affect surgical planning of pulmonary lobectomy and segmentectomy . 
 accessory fissure in the right upper lobe other than due to the anomalous course of azygos vein is very rare . 
 we report a case of non - azygos accessory fissure , between the apical and the anterior segments of right upper lobe , along with superior and inferior accessory fissures in the right lower lobe . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION