A girl aged 5 years presented with a cough and difficulty breathing of one week’s duration. She had no known disease, and the physical examination was unremarkable. The posterior-anterior chest radiograph showed an abnormally oriented rib in the upper right side of the chest (Fig. 1). The patient underwent a low-dose CT scan of the chest without contrast for further evaluation. The CT scan revealed the presence of a bifid intrathoracic rib protruding into the lung parenchyma (Fig. 2, Movie). Since the patient’s symptoms were mild, conservative treatment was initiated and a follow-up visit scheduled.

Figure 1.

Anterior–posterior chest radiograph showing an abnormally oriented rib in the right side (arrowheads).

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Figure 2.

(a) Axial and (b) coronal chest CT images evincing the intrathoracic rib (arrowheads). (c) Three-dimensional volume reconstruction chest CT image of the right lung demonstrates the parenchymal indentation of the intrathoracic rib (arrows).

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An intrathoracic rib, also known as a thoracic rib or slipping rib syndrome, is an extremely rare anomaly of the chest wall in which a normal, supernumerary or bifid rib is located within the chest cavity.1 The clinical manifestations of intrathoracic rib can include sharp or dull pain, difficulty breathing or shortness of breath and a palpable lump or bulge near the involved rib.1 The management of this type of malformation typically involves a combination of conservative measures and, in severe cases, surgical intervention.2 A chest CT scan allows precise visualization of the tubular shape and curvature of the intrathoracic rib and can be used to guide surgery.1,2