Azygo-esophageal recess

The azygoesophageal recess (also termed “Holzknecht space” or “retroesophageal recess/pouch”) represents a mediastinal recess into which the edge of the right lower lobe extends. This space lies anteriorly to the spine, it is limited superiorly by the azygos arch and it extends to the level of the aortic hiatus inferiorly. It is bordered anteriorly by the left atrium and medially by the esophagus and the azygos vein.

The interface caused by the right lower lobe outlining the medial limit of the azygoesophageal recess can be appreciated on frontal chest radiographs.

Normal radiographic appearance:

The azygoesophageal recess is seen on a frontal radiograph as a vertically oriented interface.

• In its upper third it may be straight or show mild leftward convexity. Right superior convexity may be seen in children and younger adults.

• The middle third of the recess may be the most variable in the appearance but typically is straight edged or demonstrates mild leftward convexity.

• In its lower third it usually appears as a straight edge.

The azygoesophageal recess has reportedly been seen on 51,5% of posteroanterior chest radiographs.

Abnormal radiographic appearance:

Abnormal contour, convexity or disappearance of this interface suggests disease affecting the middle and posterior mediastinal compartments such as lymphadenopathy, bronchopulmonary-foregut malformations, pleural abnormalities, left atrial enlargement, esophageal disease and hiatal hernia .