Flat Chested Kitten Syndrome in Cats

Written By Leslie Ingraham
Published: 01/22/2022Updated: 01/22/2022
Flat Chested Kitten Syndrome in Cats

What are Flat Chested Kitten Syndrome in Cats?

Flat-chested syndrome occurs in kittens just after birth, when they’re approximately three days old. Until they begin showing symptoms, they appear normal, moving around and actively suckling with their littermates. But after a few days, pet parents may notice that a kitten’s chest appears to be flattened somewhat, the kitten stops feeding, and may have some difficulty breathing. If not addressed, flat-chested kitten syndrome can lead to malnutrition, failure to thrive, and death. 

Kittens with this syndrome often spontaneously get better with no intervention. In more severe cases, veterinarians can usually support the feline until they’re strong enough to get well on their own. Because there isn’t much written or taught about flat-chested kitten syndrome (FCKS) and most cases are anecdotal in nature, pet parents and veterinarians may wrongly choose to euthanize inflicted kittens. But this may not be necessary.

Symptoms of Flat Chested Kitten Syndrome in Cats

As the condition’s name implies, the hallmark sign of flat-chested kitten syndrome is a slightly to moderately flattened chest, as though it has been stepped on. The ribs curve round from the spine normally, but as they reach the cartilage that attaches them to the sternum, the chest cavity looks flat instead of curving downward. This shape is not the result of bending of the ribs, but rather by a change in the joint angle where the ribs meet the cartilage.This causes:

  • Labored breathing
  • Failure to nurse
  • Lethargy
  • Weight loss or failure to gain weight

The flat chest and other symptoms may last only hours or days, and those kittens who survive typically have no symptoms in adulthood.

Causes of Flat Chested Kitten Syndrome in Cats

Once thought to be genetic, it is now accepted that there may be other contributing factors that cause or influence flat-chested kitten syndrome as well. While Burmese, Bengals, Maine Coons, Oriental longhairs and Oriental shorthairs seem to be most likely to have the condition, the numbers may be skewed because of cultural reporting tendencies among these breeder groups. 

Some of the factors that are now theorized to contribute to the appearance and severity of flat-chested kitten syndrome include:

  • Genetics
  • Environmental influences such as the mother cat’s nutritional and psychological status
  • Large size and robustness of the kitten 
  • Development of colic in the newborn
  • Lung collapse or failure to develop
  • Gender: 56 percent of cases are males versus 44 percent females
  • Lack of a surfactant in the alveoli of the lungs that keeps them from sticking together
  • Diaphragmatic spasm
  • Feline herpes virus

When kittens are born, their lungs aren’t fully expanded. This happens gradually over a few days. If something hinders or interrupts the process, the lungs don’t push adequately against the chest wall to shape it correctly.

A connection may be made between the biggest, most robust kittens, often the males, and the force with which they nurse. That, combined with ingestion of a large amount of milk, can cause colic. Colic expands the abdomen with milk and air, which doesn’t allow the chest to expand normally and a collapsed lung can result, followed by flat-chested kitten syndrome. 

Infections, specifically feline herpes, have been noted in cultures of saliva from kittens with flat-chest syndrome. A cause-and-effect case has not yet been made, but vets may choose to treat potential infections as part of their overall treatment plan.

Diagnosis of Flat Chested Kitten Syndrome in Cats

It’s important to take your kitten to the veterinarian as soon as possible after you notice that their chest is becoming flattened. The vet will examine the kitten, noting chest shape and the presence of symptoms like labored breathing. A chest X-ray can show images of the chest flattening from both the front and side of the kitten. It likely will also show sharp angulation changes in the connection point of the ribs with their cartilage.

The veterinarian will want to know when the kitten began developing the appearance of a flat chest, and whether breathing and nursing have been affected. It’s helpful to be weighing the litter daily to note any weight loss or failure to grow, and passing that information on.

The presence of colic symptoms will further help in making the correct diagnosis. Colic causes a distended abdomen and pain.

The vet may want to check the kitten’s respiratory status by testing blood for its oxygen level. This can be done by drawing blood and testing it directly, or using pulse oximetry which is non-invasive and painless.

Treatment of Flat Chested Kitten Syndrome in Cats

Kittens with mild cases of the syndrome often recover completely without any treatment. If the kitten is feeding adequately and is able to move around without major respiratory problems, it’s common to let it heal itself without intervening. Close monitoring is necessary, as the kitten’s condition may worsen suddenly.

There are various treatments utilized by a veterinarian when they have identified the presence of flat-chested kitten syndrome. They include:

Oxygen replacement

Kittens who are exhibiting symptoms of inadequate respirations may be treated with oxygen to supplement the air around them. This may be done with a tiny oxygen cannula or mask if the kitten is fairly still, or an oxygen tent for part of the kitten’s day. Care must be taken to regulate the amount of oxygen in a tent to avoid over-pressurizing the lungs or creating unhealthy oxygen levels.

Assisted nutrition

If the kitten isn’t nursing normally, supplementing their intake with a feeding tube may be necessary to avoid malnutrition. The aim is to keep the kitten growing while its lungs and chest cavity normalize. By three to four weeks of age, most kittens will be back nursing with their littermates.


Some veterinarians will treat flat-chested kittens with antibiotics and steroids. Antibiotics combat present or potential lung infections like pneumonia, and corticosteroids speed up the healing process in the lung tissue. Typically, the antibiotic used is Amoxicillin and the steroid is Dexamethasone. Antibiotics may also help to prevent infections secondary to the use of the steroid as well.

External splints

External splints, usually in the form of cloth bands tied firmly around the stomach area, or part of a plastic bottle taped in place over the abdomen, can assist the body and lungs in expansion and formation of a normal chest cavity shape. Typically, splints are only worn for about a week. The use of splints is dependent on whether the kitten will tolerate them – some do well with them and others don’t. 


Massage has been recommended in some cases of flat-chested syndrome because it helps the kitten to relax so the chest is flexible and not held tightly. Most kittens enjoy gentle massage and submit to it willingly.

Nutritional support of the nursing mother

To improve the nutritional value of her milk and promote normal fetal and kitten development, the mother cat may be fed highly nutritious, meat-based food during pregnancy and while nursing. Taurine and potassium supplements are thought to help as well. Taurine is an essential amino acid, and potassium aids in normal fetal development and health of kitten lungs and muscles. 

Liquid paraffin (mineral oil) for colic

Mineral oil aids in the passage of gas from the kitten’s abdomen, relieving the upward pressure of the stomach on the diaphragm and chest cavity which contributes to flat-chested syndrome.

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Recovery of Flat Chested Kitten Syndrome in Cats

In cats that survive the first few weeks with flat-chested kitten syndrome, recovery is usually speedy and permanent. By the time the kitten is six months old, all symptoms should have passed and the babe will be moving, eating, and breathing normally.

Periodic follow-up appointments during the kitten’s first year ensure that complications like secondary pneumonia or other conditions have not appeared before the flat-chested kitten syndrome is resolved completely. A physical examination and observation are generally the focus of the visits, along with weight and activity reporting by the pet parent.

Once the kitten is a year old, there is no need for the same level of watchfulness as they are expected to continue to grow and thrive normally.

Flat-chested kitten syndrome in cats can be expensive to treat. If you suspect your kitten is at risk of developing this syndrome, start searching for pet insurance today. Wag! Wellness lets pet parents compare insurance plans from leading companies like PetPlan and Embrace. Find the “pawfect” plan for your pet in just a few clicks!

Cost of Flat Chested Kitten Syndrome in Cats

Average cost of treating Flat-chested Kitten Syndrome: $100 - $400

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