Pectus excavatum (flat chest syndrome) is a relatively common congenital disease of dogs characterized by deformation of the sternum.
Although the exact cause is unknown, it is believed that unbalanced overgrowth in the costochondral regions pushes the sternum inward. The congenital deformity may produce a convex (carinatum) or concave (excavatum) appearance to the ventral aspect of chest wall. Some cases spontaneously resolve as the dog matures.
Familial occurrence of this disease suggests a autosomal-recessive disease, but diet may also play a role in pathogenesis.
Respiratory distress is the clinical sign most frequently observed. Chest asymmetry is quite variable and respiratory distress may be associated with displacement of the organs or restriction of ventilation. The deformity is generally in the caudal part of the sternum, but it has been reported in the cranial part of the sternum.
Degenerative changes and narrowing of the intersternebral spaces usually are not significant clinically. Malformation of sternebrae may accompany other congenital anomaly such as peritoneopericardial diaphragmatic hernia.
Diagnosis is usually based on radiography, but electrocardiography and echocardiography are recommended to detect any underlying cardiac abnormalities.
External surgical splinting of the sternabrae is often curative and surgical correction is warranted in cases where cardiac anomalies coexist.
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