Abnormal rib cage morphology Bell-shaped thorax Constricted, bell-shaped thorax HP:0006664 UMLS:C1865186 Narrow, bell-shaped thorax Bell-shaped chest HP:0006626 HP:0001591 A bell-shaped thorax is a non-specific finding. In newborns, bell-spahed thorax can indicate a history of intrauterine neuromuscular abnormalities. The rib cage has the shape of a wide mouthed bell. That is, the superior portion of the rib cage is constricted, followed by a convex region, and the inferior portion of the rib cage expands again to have a large diameter.