Pectus excavatum

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Multiple cartilaginous exostoses
Hemivertebra
Flat-chest syndrome

A number of chest wall deformities have been described in cats. Pectus excavatum is a congenital deformity of the thoracic wall characterized by abnormal traction of the skeletal tissues and defective osteogenesis as well as chondrogenesis, resulting in a lack of rigidity of skeletal tissues[1].

The two most common are pectus excavatum ("funnel chest") and flat chest (FCK). There are over a dozen reports about pectus excavatum in the literature, including papers describing surgical correction, but very little about FCK. It is important to understand the difference between the two conditions so they can be identified correctly[2].

  • Funnel Chest (Pectus excavatum)

Pectus excavatum or funnel chest is an uncommon congenital anomaly of the chest wall, characterized by the dorsal deviation of the caudal sternum and associated costal cartilages or a ventral to dorsal narrowing of the entire thorax[3].

In severe cases, the lack of space compresses the heart and lungs. Common signs in moderate to severely affected cats include exercise intolerance, trouble breathing, cough, weight loss or failure to gain weight[4]. Funnel chest quite often appears at about 5 - 6 weeks of age, although the abnormality obviously exists at birth and growth exacerbates or worsens the predisposition.

  • Flat Chest

In FCK, the ribcage is angled sharply at the costochondral junction, causing the ventral part of the chest to be flattened. FCK varies from very mild to very severe and life-threatening. The condition is not apparent at birth, but becomes obvious within the first few weeks of life. Mildly affected kittens may appear perfectly normal as adults.

Clinical signs

Abnormal alignment of the sternum and costal cartilages are responsible for compressive cardiopulmonary dysfunction resulting in exercise intolerance, tachypnea, cyanosis, cardiac murmur, arrhythmias, or respiratory distress[5].

Moderate to severely affected kittens will have difficulty breathing and poor weight gain. The worst affected kittens will die. FCK has been reported in many breeds of cats. Some FCK kittens also have a spinal curvature or may have pectus excavatum. A 1997 study in the U.K. reported that 3 to 4% of all Burmese born there are affected with FCK. The same study tried to evaluate potential causes and concluded that the defect is inherited, but must also be influenced by some other factors, possibly environmental or nutritional. For example, Burmese kittens in the study had much higher blood and skeletal muscle taurine levels than normally expected for cats[6]. It is unknown what association these high taurine levels may have with FCK. No association between FCK and any particular diet or any particular dietary supplements has been found[7].

Diagnosis

DIagnosis may be made simply by phsyical examination, but definitve diagnosis requires radiological confirmation of skeletal abnormalities of the chest cavity.

Treatment

Radiographic findings and surgical procedures using cylindrical external splints (C: Case No.1) and U-shaped external splint (D: Case No.2). The caudal sternebrae were dorsally displaced (A: Case No. 1). Dorsal deviation of caudal sternebrae was reduced (B: Case No. 1). Stay sutures were placed around the sternebrae from the manubrium cranially, to the xiphoid caudally (E: Case No. 1). All stay sutures pass through the holes on the apex of the splint using an 18-gauge needle (F: Case No. 2). Mosquito hemostats are used to hold the ends of the individual stay sutures (G: Case No. 2). All stay sutures were tied securely (H: Case No. 2). The splint was held in place with umbilical tapes (I: Case No. 2). Courtesy Yoon et al (2008)

Surgical intervention has been reported using an open approach to the sternum with osteotomy of the last sternebra and costochondral junctions of the eighth and ninth ribs bilaterally[8][9][10]

Some cats respond with conservative therapy such as using a cylindrical external splint and U-shaped external splint. These are often moulded to the individual kitten to act as a compressor.

Until more information is known about this defect, breeders should not use any affected cat in a breeding program, even if it appears normal as an adult. It would also be wise to avoid breeding a queen that has produced affected kittens with a sire that has also produced pectus excavatum kittens.

References

  1. Yoon HY et al (2008) Surgical correction of pectus excavatum in two cats. J Vet Sci 9(3):335-337
  2. © Dr Susan Little; http://www.catvet.homestead.com/FCK.html
  3. Fossum TW (2007) Small Animal Surgery. 3rd ed. St. Louis: Mosby. Pectus excavatum; pp:889–894
  4. Boudrieau R et al (1990) Pectus excavatum in dogs and cats. Comp Contin Edu Pract Vet 12(3):341-355
  5. Soderstrom MJ, Gilson SD & Gulbas N (1995) Fatal reexpansion pulmonary edema in a kitten following surgical correction of pectus excavatum. J Am Anim Hosp Assoc 31:133–136
  6. Sturgess C (1995) Flat chested kittens - does taurine have a role to play? Burmese Cat Club News (U.K.), 12:8
  7. Fossum TW et al (1989) Pectus excavatum in eight dogs and six cats. J Am Anim Hosp Assoc 25:595-605
  8. Mestrinho LA et al (2012) Open surgical correction combined with an external splint for correction of a non-compliant pectus excavatum in a cat. J Feline Med Surg 14(2):151-154
  9. McAnulty JF & Harvey CE (1989) Repair of pectus excavatum by percutaneous suturing and temporary external coaptation in a kitten. J Am Vet Med Assoc 194(8):1065-1067
  10. Sturgess CP et al (1997) Investigation of the association between whole blood and tissue taurine levels and the development of thoracic deformities in neonatal Burmese kittens. Vet Rec 141:566-570