Azygos lobe explained

In human anatomy, an azygos lobe is a normal anatomical variation of the upper lobe of the right lung.^[1] It is seen in 0.3% of the population.^[2] Embryologically, it arises from an anomalous lateral course of the azygos vein,^[3] in a pleural septum within the apical segment of the right upper lobe or in other words an azygos lobe is formed when the right posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers as the azygous fissure, that invaginates into the upper portion of the right upper lobe.^[1]

Clinical significance

An azygos lobe is usually an incidental finding on chest x-ray or CT scan. It is asymptomatic and not associated with any morbidity.^{[4] [5]} However, it can cause technical problems in thoracoscopic procedures.^[6] The presence of the azygos lobe could alter the normal location of the superior vena cava or may be associated with other anomalies, including esophageal atresia or intrapulmonary right brachiocephalic veins.^[7]

Additional images

Further reading

• Sidhu R, Dhanadia A, Shah H, Chudasama N . Eluding normal variant . Lung India . 32 . 3 . 289–91 . May 2015 . 25983422 . 4429398 . 10.4103/0970-2113.156258 . free .
• Mata J, Cáceres J, Alegret X, Coscojuela P, De Marcos JA . Imaging of the azygos lobe: normal anatomy and variations . AJR. American Journal of Roentgenology . 156 . 5 . 931–7 . May 1991 . 2017954 . 10.2214/ajr.156.5.2017954 .

Notes and References

1. Web site: Amini B . Azygos lobe Radiology Reference Article Radiopaedia.org . Radiopaedia.
2. Yurasakpong . Laphatrada . Yammine . Kaissar . Limpanuparb . Taweetham . Janta . Sirorat . Chaiyamoon . Arada . Kruepunga . Nutmethee . Meemon . Krai . Suwannakhan . Athikhun . 2021-05-07 . The prevalence of the azygos lobe: A meta‐analysis of 1,033,083 subjects . Clinical Anatomy . 34 . 6 . 872–883 . 10.1002/ca.23737 . 33908686 . 233428865 . 0897-3806.
3. Demos TC, Posniak HV, Pierce KL, Olson MC, Muscato M . Venous anomalies of the thorax . AJR. American Journal of Roentgenology . 182 . 5 . 1139–50 . May 2004 . 15100109 . 10.2214/ajr.182.5.1821139 . free .
4. Akhtar J, Lal A, Martin KB, Popkin J . Azygos lobe: A rare cause of right paratracheal opacity . Respiratory Medicine Case Reports . 23 . 136–137 . 2018-01-01 . 29719800 . 5925948 . 10.1016/j.rmcr.2018.02.001 .
5. Caceres J, Mata JM, Andreu J . The azygos lobe: normal variants that may simulate disease . European Journal of Radiology . 27 . 1 . 15–20 . March 1998 . 9587765 . 10.1016/s0720-048x(97)00146-0 .
6. Sieunarine K, May J, White GH, Harris JP . Anomalous azygos vein: A potential danger during endoscopic thoracic sympathectomy. . Australian and New Zealand Journal of Surgery . August 1997 . 67 . 8 . 578–9 . 10.1111/j.1445-2197.1997.tb02046.x . 9287933 .
7. Al-Mnayyis . Asma’a . Al-Alami . Zina . Altamimi . Neveen . Alawneh . Khaled Z. . Aleshawi . Abdelwahab . 2020-07-10 . Azygos Lobe: Prevalence of an Anatomical Variant and Its Recognition among Postgraduate Physicians . Diagnostics . 10 . 7 . 470 . 10.3390/diagnostics10070470 . 2075-4418 . 7400486 . 32664403. free .