Imaging description

Horseshoe lung is a rare congential malformation characterized by fusion of the posterior basilar segments of the right and left lower lobes through a partial parietal pleural defect. On imaging, this is seen as fusion of the right and left lower lobes posterior to the heart [1–3] (Figure 9.1). The majority of cases of horseshoe lung are associated with right lung hypoplasia and approximately 80% are associated with partial anomalous pulmonary venous return from the right lung to the inferior vena cava or right atrium (Scimitar syndrome) [1–3].

Importance

Horseshoe lung itself is usually asymptomatic, however, there are a number of associated abnormalities that may be symptomatic. As stated previously, the most common associated abnormality is Scimitar syndrome. Absence of a pulmonary artery, pulmonary sling (Figure 9.1), accessory diaphragm, or pulmonary sequestration have also been reported [1–3]. Therefore, when horseshoe lung is identified, careful attention to the remainder of the chest is warranted in an attempt to identify any associated abnormalities.