Accessory lobe of lung

This code describes the presence of an additional, typically small, and often non-functional lobe of lung tissue that is separate from the main pulmonary lobes. This anomaly is a congenital malformation resulting from abnormal lung bud development. It may be asymptomatic or, less commonly, associated with respiratory symptoms if it becomes infected or compresses adjacent structures.

Use this code when diagnostic imaging (e.g., chest X-ray, CT scan) identifies an accessory lobe of the lung. Documentation should clearly state the presence of an accessory lobe, often noted as an incidental finding during imaging performed for other reasons. This code is appropriate for both symptomatic and asymptomatic presentations of this congenital anomaly.

• Do not confuse an accessory lobe with a sequestered lung, which has a separate arterial supply and venous drainage.
• Code only when the accessory lobe is explicitly documented; do not assume based on vague imaging findings.
• If the accessory lobe is causing specific symptoms (e.g., infection), code the symptom(s) in addition to this anatomical anomaly.