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 Table of Contents  
Year : 2019  |  Volume : 3  |  Issue : 1  |  Page : 30-32

The lesser known lobe

1 J.S.S. Medical College, Mysore, Karnataka, India
2 Cardiologist, Baliga Diagnostics Pvt Ltd, Bangalore, Karnataka, India
3 Senior Cardiologist, Fortis Hospitals, Bangalore, Karnataka, India
4 Radiologist, Lucid Diagnostics Pvt Ltd, Bangalore, Karnataka, India

Date of Web Publication15-Mar-2019

Correspondence Address:
Arun Umesh Mahtani
B306 Mantri Elegance Apartments, N. S. Palya, Next to Shopper's Stop, Bannerghatta Road, Bangalore - 560 076, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiae.jiae_29_18

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The azygos lobe was first discovered by an anatomist Dr. Heinrich August Wrisberg in the year 1877. It is a rare normal variant of the lung usually present over the right lobe. The azygos lobe has been reported in various case reports where it has been mistaken to be a neoplasm, a bulla, or a paratracheal mass. It has implications in the field of surgery as well when this anatomic variant was discovered during sympathectomy and the approach had to be slightly altered. We present a rare case of an incidental finding of an azygos lobe impinging over the superior vena cava and causing axial alteration of the heart.

Keywords: Accessory lobe, azygos lobe, lung, superior vena cava

How to cite this article:
Mahtani AU, Baliga V, Govind S, Reddy P. The lesser known lobe. J Indian Acad Echocardiogr Cardiovasc Imaging 2019;3:30-2

How to cite this URL:
Mahtani AU, Baliga V, Govind S, Reddy P. The lesser known lobe. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2019 [cited 2020 Sep 29];3:30-2. Available from: http://www.jiaecho.org/text.asp?2019/3/1/30/254252

  Introduction Top

The lung in the human body is divided into different lobes due to fissures running across it. The left lung has one fissure namely the oblique fissure dividing it into a superior and an inferior lobe, whereas the right lung has two fissures namely the horizontal and the oblique fissures. This divides it into three separate lobes namely superior, middle, and inferior lobes. The azygos lobe, however, is an accessory lobe predominantly located over the right lung.[1],[2] It is a rare normal anatomic variant usually occurring due to a difference in migration of the azygos vein cutting across the lobe. It is not a true lobe and does not have its own bronchopulmonary segment or bronchus. Embryologically, it is part of the right upper lobe and its blood supply originates from the same region.[3] The prevalence of such a variant ranges between 0.4% on chest radiograph and 1.2% on chest computed tomography (CT) scan.[4] Here is a case report of an azygos lobe impinging upon the superior vena cava (SVC), causing extrinsic compression along with a change in the axis of the heart.

  Clinical Presentation Top

A 36-year-old Indian female, a homemaker by occupation, presented to the outpatient department with complaints of early morning headache, slight upper-chest discomfort, and excessive fatigue for 1 week. Prior to this, she was very well, keeping herself active with regular walks and yoga twice a week. There was no significant past medical or family history of ischemic heart disease, hypertension, or diabetes. She has had no clinical interventions in the past and had never smoked.

On examination, her pulse rate was 80 beats/min, regular, and blood pressure recording was 200/80 mmHg in the sitting position. General physical examination showed no other clinical abnormalities. Cardiovascular and respiratory system examination was normal, and there were no neurological signs.

An electrocardiogram (ECG) was ordered which showed [Figure 1] a widespread T-wave inversion from V1 to V5 with an oddly positioned axis. She was referred to a tertiary care center for chest X-ray and echocardiography.
Figure 1: T-wave inversion from V1 to V5 with an oddly positioned axis

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A chest X-ray posteroanterior view was performed which demonstrated a possible accessory lobe over the apical region of the right lung. The remainder of the chest X-ray was normal.

Echocardiography revealed normal-sized left and right heart with good systolic function. Valves appeared morphologically normal with normal forward flow seen across them. However, turbulent flow was noted across the SVC with mild external compression of the right ventricle and SVC [Figure 2].
Figure 2: (a) High parasternal axis view showing extracardiac compression of the right atrium and superior vena cava. (b) An off-axis apical four-chamber view showing turbulent superior vena cava flow. (c) An off-axis high parasternal short-axis view showing turbulent superior vena cava flow. (d) Doppler velocities of superior vena cava flow showing abnormally high velocities

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Based on the findings of the chest X-ray and echocardiogram, we conducted a CT scan of the thorax which confirmed the presence of an azygos lobe compressing the SVC [Figure 3].
Figure 3: (a, d and e) Axial computed tomography image showing an azygos lobe and the corresponding azygos vein. The azygos lobe can be seen impinging over the superior vena cava. (b and c) Coronal computed tomography image showing an azygos lobe and the corresponding azygos vein. The azygos lobe can be seen impinging over the superior vena cava

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  Discussion Top

Diagnostic focus and assessment

In the case report discussed, the peculiar ECG [Figure 1] finding provided the catalyst to further investigate this patient and find out the underlying cause of her symptoms and clinical finding of hypertension at such a young age. The echocardiographic findings prompted the requirement for further investigation that led to the diagnosis of the azygos lobe.

The first sign of something being amiss was when routine parasternal long-axis (PLAX) view showed normal structures which could be viewed properly only in an off-axis PLAX plane [Figure 2]. This unusual finding was confirmed on high parasternal short-axis [Figure 2]a and in the apical four-chamber views [Figure 2]c. On closer examination in these views and when viewed from multiple angles, there appeared to be an extracardiac compression at the base of the heart on the right side [Figure 2]b. An abnormally turbulent flow was noted which was subsequently identified as obstructed SVC flow probably due to the extracardiac compression [Figure 2]d. Apart from these findings, the heart was structurally normal and Doppler hemodynamics were normal.

It should be noted that all cases of azygos lobe may not present in the same way, and usually it is an incidental finding on a chest X-ray or a CT scan when a patient is being evaluated for other pathologies.

Therapeutic focus and assessment

Since this was an anatomical variant, no further clinical intervention was required and the patient was commenced on a simple course of antihypertensive medication. She was advised routine follow-up for blood pressure monitoring and a recent clinic visit revealed a normal blood pressure with no symptoms.

This case report sheds light on the lesser known azygos lobe and its incidental finding in a patient that presented for a routine clinical evaluation.

An azygos lobe is a rare anatomical variant.[1],[2] It is usually seen over the right lung.[1] An azygos lobe can mimic a pathology such as a lung abscess, a bulla, or even a neoplasm.[5] It can also compress structures such as the SVC[6] and the heart and can obscure a part of the sympathetic chain.[7] Radiographic studies become essential to confirm the diagnosis and to rule out other pathology.

Previously, the pathology and clinical findings seen in accessory and azygos lobes were not clearly described due to the paucity of cases encountered in clinical practice. Over time, numerous case reports have since been published.

The azygos lobe was first described in the year 1877 by a German gynecologist and (nominal professor in anatomy) anatomist Dr. Heinrich August Wrisberg in his study titled “Lobus Wrisbergi.” It was detected radiologically only 46 years later.[8]

The azygos lobe develops when a precursor of the azygos vein called the posterior cardinal vein takes an alternative route to migrate to the hilum of the lung. In normal individuals, the posterior cardinal vein migrates cephalad along the vertebral column, following which it arches over the apex of the right lung and slides down medially next to the hilum to become the azygos vein.[9] However, in case of patients with an azygos lobe, the posterior cardinal vein cuts across the apex of the right lobe dragging along with it part of the parietal pleura and visceral pleura to migrate near the hilum. In such situations, we find that the azygos vein is completely supported with the help of parietal pleura which is termed as the mesoazygos.[10] The azygos lobe is very important when it comes to thoracoscopic surgeries and needs to be ruled out preoperatively to prevent surgical complication in cases involving sympathectomy for hyperhidrosis.[11] Furthermore, there have been previous reports indicating a link between spontaneous pneumothorax and presence of an azygos lobe.[12],[13],[14]

Cases of cancer in an azygos lobe have also been published. Only three such cases have been documented in the history of medical literature. Two cases showed non-small cell lung carcinoma and one case showed small cell lung cancer.[15] Initially, no therapeutic measures were performed, but over time, therapeutic procedures such as video-assisted thoracic surgery (robot assisted) have been attempted to treat the underlying condition.[16]

  Conclusion Top

Despite being an anatomical variant, the azygos lobe has implications not only in medicine but also in surgical field. It becomes important to confirm the presence of this variation using radioimaging.


I would like to thank Dr. B Vivek Baliga, Dr. Puneeth Reddy, and Dr. Satish Govind for providing help in revising the manuscript.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understand that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Arai H, Inui K, Kano K, Nishii T, Kaneko T, Mano H, et al. Lung cancer associated with an azygos lobe successfully treated with video-assisted thoracoscopic surgery. Asian J Endosc Surg 2012;5:96-9.  Back to cited text no. 1
Patil SJ. Azygos lobe a review. Int J Clin Surg Adv 2013;1:17.  Back to cited text no. 2
Akhtar J, Lal A, Martin KB, Popkin J. Azygos lobe: A rare cause of right paratracheal opacity. Respir Med Case Rep 2018;23:136-7.  Back to cited text no. 3
Pradhan G, Sahoo S, Mohankudo S, Dhanurdhar Y, Jagaty SK. Azygos lobe – A rare anatomical variant. J Clin Diagn Res 2017;11:TJ02.  Back to cited text no. 4
Felson B. The azygos lobe: Its variation in health and disease. Semin Roentgenol 1989;24:56-66.  Back to cited text no. 5
Proto AV, Speckman JM. The left lateral radiograph of the chest. Part 1. Med Radiogr Photogr 1979;55:29-74.  Back to cited text no. 6
Sieunarine K, May J, White GH, Harris JP. Anomalous azygos vein: A potential danger during endoscopic thoracic sympathectomy. Aust N Z J Surg 1997;67:578-9.  Back to cited text no. 7
Krivinka R. Uber einem fall von linksseitigem vorkommen des lobus Wrisbergi. Rontgenpraxis 1939;11:234-7.  Back to cited text no. 8
Thorek P, editor. Thorax: Lungs (Pulmones) in Anatomy in Surgery. 2nd ed. Philadelphia: JB Lippincott & Co.; 1962. p. 288-9.  Back to cited text no. 9
Ndiaye A, Ndiaye NB, Ndiaye A, Diop M, Ndoye JM, Dia A, et al. The azygos lobe: An unusual anatomical observation with pathological and surgical implications. Anat Sci Int 2012;87:174-8.  Back to cited text no. 10
Baumgartner FJ, Kalinowski A, Grant S. Endovascular repair of injury to a persistent sciatic artery. Tex Heart Inst J 2009;36:61-4.  Back to cited text no. 11
Asai K, Urabe N, Takeichi H. Spontaneous pneumothorax and a coexistent azygos lobe. Jpn J Thorac Cardiovasc Surg 2005;53:604-6.  Back to cited text no. 12
Sadikot RT, Cowen ME, Arnold AG. Spontaneous pneumothorax in a patient with an azygos lobe. Thorax 1997;52:579-80.  Back to cited text no. 13
Monaco M, Barone M, Barresi P, Carditello A, Pavia R, Mondello B, et al. Azygos lobe and spontaneous pneumothorax. G Chir 2000;21:457-8.  Back to cited text no. 14
Imširović B, Mekić-Abazović A, Omerhodžić I, Zerem E, Vegar-Zubović S. Atypical localization of lung cancer located in lobus v. Azygos. Med Glas (Zenica) 2012;9:408-11.  Back to cited text no. 15
Fukuhara S, Montgomery M, Reyes A. Robot-assisted azygos lobectomy for adenocarcinoma arising in an azygos lobe. Interact Cardiovasc Thorac Surg 2013;16:715-7.  Back to cited text no. 16


  [Figure 1], [Figure 2], [Figure 3]


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