Pectus carinatum sounds a lot more imposing than the common term for this canine chest deformity: pigeon-chested or pigeon-breasted. Also known as pectus galinatum, this condition occurs rarely in dogs, but when it does it's obvious in puppyhood. Beagles are more often afflicted than other breeds, as are dogs who are closely inbred. Dogs with pectus carinatum should not be bred.
The Normal Canine Chest
A dog normally has 13 pairs of ribs that come down from the spine's thoracic vertebrae to the breastbone, or sternum. Rib pairs 12 and 13 -- the so-called "floating ribs" -- don't always link up to the breastbone. The breastbone consists of three different bones -- the manubrium, the keel and the xiphoid process. The manubrium, the breastbone's front, upper part, is near the first two rib pairs and heads upward toward the area of the esophagus. The keel, also known as the body, is the bone between the dog's front legs, while the xiphoid process takes up the rear of the sternum.
In dogs with pectus carinatum, the manubrium comes to a point rather than curving. That bump can be felt even in young puppies. The deformity occurs far more frequently in males than females. Dogs born with pectus carinatum often suffer from other issues, including scoliosis, or curvature of the spine. In severely deformed dogs, pectus carinatum can affect lung and heart function. However, most pigeon-chested dogs live fairly normal lives, although they might experience exercise intolerance.
Pigeon-chested dogs often suffer from other abnormalities related to breastbone deformity. These include short ribs, in which the ribcage doesn't go far back enough into the abdomen, resulting in a lack of structural support. Such dogs might also exhibit abnormally thin waists, known by the term "herring-gutted." In some breeds, such as the greyhound, these thin waists are a normal part of the dog's physiology and not an indication of pectus carinatum.
Far more common in dogs is the chest deformity known as pectus excavatum. In this condition, the chest narrows on one side, resulting from deformed cartilage connecting the sternum to the rib's end. The dog's chest appears concave or flat. Dogs born with pectus excavatum often exhibit breathing difficulties. Severely affected dogs usually have short life spans unless they undergo surgery to correct the deformity.