EXPLORE!

Lobe of Azygos Vein and its Clinical Significance

  1018 Views

    13 April 2022

Abstract

Although an azygos lobe is a rare anomaly of the lung, its radiologic appearance has been well-defined. Clinically, the azygos lobe has been accepted as a normal variation that can simulate various diseases. So, the detection of this anomaly and classification of its precise anatomical features are important not only to differentiate this anomaly from other pathological conditions but also to alert the surgeons to potential problems during surgery. The lobe of azygos lobe was observed in one case in the right lung of 50-year-old male cadaver. The azygos lobe was situated medial to the superior lobe and superior to the hilum of right lung. Because of the clinical importance and rare occurrence, the anomaly is compared and discussed with other articles.

Introduction

Azygos lobe is a small accessory lobe sometimes found on the upper part of the right lung; separated from the rest of the upper lobe by a deep groove lodging the azygos vein. It is different from other accessory lobes or anomalies of lung, the aberrant azygos vein crosses the apex of the lung. The term ‘azygos lobe’ has been used not merely for this particular accessory lobe, cutoff from the upper and medial part of the lung, above the hilum, by a fold of parietal pleura containing the vena azygos major, but also for other accessory lobes, both those in the upper part of the lungs and that found occasionally at the base, to which Allen (1882) gave the term ‘Lobus cavae’. The azygos lobe has been documented in both the right and the left lungs and this anomaly has been found on anatomic dissections at a frequency of 1%, and at an approximate frequency of 0.4% on chest radiograms (Boyden, 1952). As this anomaly may simulate other pathological conditions on chest radiograms, recognition is essential. So, detection of this anomaly is important to differentiate from other conditions of the lung and also to alert the surgeons about potential problems during surgery.

Case Report

The present study was performed on a 50-year-old male cadaver during routine anatomical dissection. An azygos lobe was found on the right lung. This lobe was separated from the rest of the right lung by azygos fissure and azygos vein was lying at the bottom of the azygos fissure. Length measurements were made on the right lung and the azygos lobe from the mediastinal aspect. The distance between the right lung apex and the base was 19 cm and the length of azygos lobe was 5.1 cm. The lobe was 2.2 cm deep at the apex and lower parts. The azygos vein was supported by a mesenteriole of parietal pleura (mesoazygos). The vein terminated in brachiocephalic vein at a higher level than normal. The bronchus and vessels of the azygos lobe were dissected. It was observed that azygos lobe was supplied by apical and posterior segmental branches of the artery. Except for the azygos lobe, we did not observe any other fissure and lobe variations. Both lungs were in normal anatomical situations.

Discussion

The first mention of the existence of an accessory lobe in the right apex was found to have been made by Wrisberg in 1778, from anatomical studies, the structure being sometimes designated as the ‘lobus Wrisbergi’. Since then a number of anatomical observers have reported instances of the occurrence of this lobe. Stibbe in 1919 and Cairney in 1923 observed similar cases.

This accessory lobe of the azygos vein is caused by the partial cutting off from the upper lobe of right lung of a portion of lung tissue, by means of a sort of mesoazygos in the free edge of which lies the azygos vein. Normally, the azygos vein proceeds up the posterior mediatinum on the anterior surfaces of the vertebral bodies slightly to the right of the mid-line, passing over the intercostal arteries, with the thoracic aorta and thoracic duct to the left. At the fourth, or sometimes the third, dorsal vertebra it bends forward and to the right, curves over the right bronchus and right pulmonary artery and descends slightly to open into the posterior surface of the superior vena cava. In describing variations of the lobes and fissures the azygos major vein may be displaced outwards so that, instead of curving over the root of the lung, it may make a deep fissure in the upper part of the lobe, marking off an extra lobe. It is apparent that lateral displacement of the vein represents a maintenance of the fetal position. Bendick and Wessler (1928) confirmed the fact radiologically by means of opaque injections of the bronchial tree, that the accessory lobe was supplied by a branch of the eparterial bronchus.

This anomaly must be differentiated from a substernal thyroid gland, a large thymus and pleural bands. The lobe may also be simulated by the edge of an annular bronchiectasis at the apex, by the edge of cavities and of a spontaneous circumscribed pneumothorax.

References

  1. Allen, W. A variety of pulmonary lobation and its relations to the thoracic parietes, as illustrated by comparative anatomy and abnormalities in the humansubject. J. Anat. Physiol 1882;16(Pt 4):605-14.
  2. Anson BJ, Siekert RG, Richmond TE, et al. The accessory pulmonary lobe of the azygos vein. Q Bull Northwestern University Medical School 1940;24:285-90.
  3. Benedick AJ, Wessler H. The azygos lobe of the lung. AJR 1928;20(1):1-6.
  4. Cairney J. The lobe of the azygos vein: note on two additional cases. J Anat 1923;58(Pt 1):54-8.
  5. Stibbe EP. The accessory pulmonary lobe of the vena azygos. J Anat 1919;53(Pt 4):305-14.
  6. Velde G. Ein eigentümlicher Schattenstreifen in der rechten Lungenspitze. Fortschr Röntgensthr 1927;36:315-8.
  7. Wessler H, Jaches L. Clinical Roentgenology of Diseases of the Chest. The Southworth Co.:Troy, NY, 1923.
  8. Wrisberg HA. Observationes anatomicae de vena azyga duplici, aliisque hujus venae varietaibus. Novis Commentariis Societatis Reg Sci Gottingen 1777;8:14.

To comment on this article,
create a free account.

Sign Up to instantly get access to 10000+ Articles & 1000+ Cases

Already registered?

Login Now

Most Popular Articles

News and Updates

eMediNexus provides latest updates on medical news, medical case studies from India. In-depth medical case studies and research designed for doctors and healthcare professionals.