Pectus excavatum

What it is

Pectus excavatum (funnel chest) is a congenital deformity of the thoracic wall in which the caudal sternebrae and their costal cartilages deviate dorsally into the thorax. The result is a thorax that is narrow from dorsal to ventral and, in severe cases, displacement and compression of the heart and lungs. The cause is not clear; an imbalance in the pull of the diaphragm and of the muscles attached to the sternum, and abnormal development of the cartilages, have been proposed. It may occur together with the "swimmer puppy" syndrome.

Who it affects

Puppies, usually noticed in the first weeks or months of life. Brachycephalic breeds (English bulldog, French bulldog, pug, Boston terrier) are overrepresented, but it occurs in other breeds.

Anatomy involved

The canine sternum has eight sternebrae: the manubrium, six intermediate sternebrae and the xiphoid process, joined by intersternebral cartilages. The costal cartilages of ribs 1 to 9 articulate with it. In pectus excavatum the caudal sternebrae and the attached cartilages are bent dorsally, so the floor of the thorax rises toward the vertebral column. The heart is often pushed to one side, usually the left.

Clinical signs

Mild cases have no clinical signs apart from a palpable depression of the caudal sternum. Severe cases show dyspnoea, tachypnoea, exercise intolerance, poor growth, recurrent respiratory infections and, sometimes, a heart murmur caused by the displacement of the heart. Other congenital anomalies should be looked for.

Diagnosis

• Palpation of a flat or concave caudal sternum.
• Thoracic radiographs (lateral and ventrodorsal) show the dorsal deviation of the sternum and the displacement of the heart. Indices that compare the width and height of the thorax or the sternum-to-vertebra distance with the size of a vertebral body are used to grade severity.
• Echocardiography if there is a murmur, to rule out concurrent heart disease.

Treatment

Asymptomatic or mild cases may need no treatment; in very young puppies, gentle lateral compression of the chest by the owner has been used while the cartilages are pliable. Moderate or severe cases in young puppies are treated with an external splint: sutures placed around the sternebrae pull the sternum ventrally toward a rigid splint shaped to the chest, left for a few weeks while the compliant chest remodels. Older dogs with a rigid thorax may need surgical correction with sternal osteotomies and internal fixation. Prognosis is good when treated early.

In the cat

Pectus excavatum also occurs in kittens and is detected in the first weeks or months of life. It must be distinguished from flat-chested kitten syndrome, in which the whole thorax is flattened dorsoventrally without the focal deviation of the caudal sternum; the two can coexist, have been described more often in the Burmese and Bengal and in related litters, which suggests a hereditary component. Many kittens with mild forms have no signs and improve as they grow; severe cases show dyspnoea, exercise intolerance and poor growth, and can die. The kitten's chest is very compliant, so an external splint with sutures around the sternum gives good results when applied early. Affected cats should not be bred and the same matings should not be repeated.

Key studies in the cat

• Charlesworth and Sturgess (2012), vaccination records: 12 of 244 Bengal kittens had thoracic wall deformities (5 pectus excavatum, 6 unilateral concavities and 1 scoliosis), more than domestic shorthairs. Pedigrees showed common ancestry.
• Holst et al. (2026), CT and pathology of affected Bengal kittens and a breeder questionnaire covering 311 litters in Sweden. Affected kittens appeared in 12% of litters, 72% were male, and stillbirths and deaths within 24 hours were more frequent in affected litters (20% versus 12%). Two thirds of affected kittens survived, and the frequency varied between sires, suggesting a genetic basis. The data come from breeders.
• Charlesworth et al. (2016), a prospective study of 10 kittens aged 10 to 15 weeks with moderate or severe pectus excavatum assessed by CT. Radiographic indices approximated CT measurements but correlated poorly with clinical signs; midline deformities caused more severe signs than lateralised ones. 6 of 7 severely affected kittens splinted for 4 weeks had excellent medium-term outcomes. The sample is very small.
• Heidgerd et al. (2026), 25 cats younger than 20 weeks treated with an external splint. 19 of 25 had tachypnoea or exercise intolerance, and 24 of 25 survived. The frontosagittal index fell from 5.44 to 2.09 and the vertebral index rose from 4.45 to 8.47, and clinical signs resolved in all. The splint was kept on for a median of 28 days; complications were pneumothorax, suture breakage, dermatitis, persistent defect and one death.