Pectus Excavatum is initially diagnosed from a visual examination of the anterior chest area. Subsequently, auscultation of the chest can reveal if other potential symptoms are present such as a displaced heart beat or a valve prolapse; there can be a heart murmur occurring caused by close proximity between the sternum and the pulmonary artery. Equally, lung sounds can be used to determine if the condition is resulting in reduced lung capacity.
Many scales have been developed by medical practitioners in order to better determine the degree of deformity in the anterior chest wall. Most of these scales are simply variants on the distance between the sternum and the spine. One such index is the Backer ratio which grades the severity of deformity based on the ratio between the diameter of the vertebral body nearest to xiphosternal junction and the distance between the xiphosternal junction and the nearest vertebral body. More recently the Haller index has been used based on CT scan measurements. Using the Haller index, a value over 3.25 is often described as severe. The Haller index is defined by the ratio of the horizontal distance of the inside of the ribcage and the shortest distance between the vertebrae and sternum.
Chest x-rays are also useful in the diagnosis of Pectus Excavatum, and can be used to great effect to determine the severity of the condition and the ensuing physiological symptoms. Some studies also suggest that the Haller index can be calculated using a chest x-ray instead of a CT scan, but only for individuals who do not have a limitation in their cardiac or respiratory functions.
Pectus Excavatum is differentiated from other disorders by a series of elimination of signs and symptoms. Pectus carinatum is excluded by the simple observation of a collapsing of the sternum rather than a protrusion. Kyphoscoliosis is excluded by diagnostic imaging of the spine, where in Pectus Excavatum the spine usually appears normal in structure and shape.