When to see a vet urgently
Contact a vet immediately if your cat has any of the following:
- open-mouth breathing or clearly laboured, rapid breathing;
- pale, grey or bluish gums or other mucous membranes with weakness;
- breathing difficulty after a fall, road accident or another impact;
- collapse, sudden deterioration or repeated vomiting with a known diaphragmatic hernia.
Find a vet near you for emergency help.
Overview
The diaphragm is a thin muscle separating the chest and abdomen and helping with breathing. A tear allows abdominal organs to enter the chest and compress the lungs and heart. This is dangerous because it impairs both breathing and circulation.
A diaphragmatic hernia is an internal structural defect, so there need not be a visible bulge in the abdominal skin. Space for the lungs may be reduced even if the ribs and skin look intact externally. The accident may also have damaged other organs.
Congenital peritoneopericardial diaphragmatic hernia, or PPDH, must be distinguished from a traumatic tear. It creates an abnormal connection between the abdomen and the pericardium, the sac around the heart. It may cause respiratory or digestive signs but can also be found during examination of an adult cat without symptoms. Treatment decisions for an incidental finding differ from emergency care for acute trauma.
Causes
The most common causes of diaphragmatic hernia include:
- trauma from being hit by a car, falling or forceful impacts;
- congenital openings formed during foetal development; in cats, these are usually peritoneopericardial hernias, which are not particularly rare and are often found incidentally on X-rays;
- tissue weakening in certain chronic diseases.
Severe blunt trauma and congenital developmental abnormalities are typical starting points. There is little evidence for tissue weakness associated with chronic disease as a usual cause in cats. A diaphragmatic hernia should therefore not be inferred from another long-term disease without imaging.
At-risk cats
- cats that go outdoors, with greater injury risk;
- young, active animals, more often involved in falls and accidents;
- kittens with a congenital diaphragmatic opening.
Congenital means the abnormality has existed since birth, rather than that diagnosis must occur in kittenhood. PPDH may become apparent later. Traumatic rupture risk mainly relates to an accident: an older or previously healthy indoor cat can also be injured in a fall, for example.
Symptoms
Symptoms depend on the opening's size and the organs involved:
- breathing difficulty and shortness of breath;
- rapid, open-mouth breathing;
- reduced appetite, vomiting or loss of appetite;
- tiredness, listlessness and weakness;
- pale mucous membranes;
- abnormal sounds on listening to the chest, with mixed respiratory and intestinal sounds;
- signs of shock in severe hernias.
Sometimes the condition remains hidden, particularly with a small opening, and signs appear only during exertion.
At home, breathing difficulty may show as reluctance to lie down, extending the head and neck or pronounced abdominal movement during breathing. Your cat may stay still and avoid movement. Do not investigate these signs by exercising or playing with them.
Mild symptoms immediately after an accident do not rule out damage. In a long-standing hernia, weight loss or intermittent digestive problems may be more prominent than respiratory signs. Nevertheless, listening findings or observations at home alone cannot confirm a hernia.
Possible complications
Without care, a hernia can lead to:
- chronic respiratory failure;
- compression of the heart and blood vessels;
- intestinal or stomach tissue death if organs become trapped;
- death.
If the stomach enters the chest and expands with gas, breathing can worsen rapidly. The blood supply to a trapped organ may also be compromised. In a long-standing hernia, adhesions can form between organs and make later surgery more difficult.
Other consequences of an accident include lung bruising, rib fractures, and air or blood around the lungs. These can worsen breathing independently or together with diaphragm damage. Care therefore extends beyond assessing the opening alone.
Veterinary investigations
Diagnosis relies on:
- chest X-rays, the main method;
- contrast studies in unclear cases;
- ultrasound to clarify organ positions;
- blood tests to assess general condition.
Breathing and circulation are assessed first. A cat with severe breathing difficulty may receive oxygen before imaging. Unnecessary handling is avoided because forcing an unstable patient into an X-ray position, for example, can worsen their condition.
X-rays look for altered normal diaphragm outlines and abdominal organs in an abnormal location. Gas-filled intestinal loops may be visible in the chest. The lungs and other traumatic injuries are assessed too. Fluid in the chest can make images harder to interpret.
Ultrasound may help identify displaced organs and chest fluid. Contrast imaging or CT is considered if ordinary imaging does not clarify the anatomy sufficiently. Blood tests do not identify a hernia alone, but help assess anaemia, organ function and abnormalities affecting anaesthesia. An ECG may monitor heart rhythm.
Treatment
Surgery repairs a traumatic diaphragmatic tear. First, the team aims to stabilise breathing and circulation and treat pain and other injuries. This does not mean every operation is delayed in the same way: a rapidly deteriorating cat or one severely affected by displacement of the stomach may need an urgent procedure.
During surgery, displaced organs are returned to the abdomen and the diaphragm opening closed. Organ blood supply and damage are assessed at the same time. A temporary chest drain may be left to remove air or fluid. The procedure's extent depends on the tear, adhesions and other injuries.
For an incidental PPDH without symptoms, monitoring rather than surgery may sometimes be chosen. Decisions consider the anatomy, possible symptoms and anaesthetic risk. Monitoring does not close the opening, and new symptoms may change the recommendation. Repair of a symptomatic congenital hernia is assessed separately.
Care after surgery
Hospital monitoring assesses breathing, oxygenation, pain and any drain. When a lung compressed for a long time expands again, fluid can develop within it, known as pulmonary oedema. Successful closure alone therefore does not determine when a cat can go home.
At home, follow the surgeon's instructions for rest and restricted movement. Becoming brighter does not mean jumping or free outdoor access is already safe. Arrange a recovery area that prevents unnecessary jumps, with food, water and the litter tray easily accessible.
Keep the surgical wound dry and prevent licking and scratching. Do not apply creams or disinfectants without specific instructions. Increasing redness, swelling, discharge, wound opening or bleeding warrants veterinary contact. New breathing difficulty needs emergency assessment and should not be regarded as ordinary recovery tiredness.
At discharge, ask for written medicine and follow-up instructions. Monitor appetite, movement, general condition and breathing at rest. Contact the practice if your cat is difficult to wake, cannot function normally or deteriorates. Agree medicine changes with the treating vet.
Prognosis
The outlook depends on the severity of respiratory and circulatory problems, the organs involved and other traumatic injuries. Adhesions in a chronic hernia can also affect surgical difficulty. Many cats recover well after repair, but the opening's size or diagnosis name alone cannot predict an individual outcome.
Prevention
- limit outdoor roaming to reduce injury risk;
- secure windows and balconies with mesh, as falls are common;
- handle your pet carefully;
- monitor cats with suspected congenital openings.
First aid for breathing difficulty after an injury
- do not place your cat on their side or press on them; transport them resting on their chest in a carrier with the lid removed;
- do not give food or water;
- keep your cat calm and cool without forceful restraint, as stress and struggling worsen breathing difficulty;
- go to the practice immediately and preferably call ahead to say you are bringing a cat with breathing difficulty.
Let your cat keep the position in which breathing is easiest. Do not force a cat resting on their chest onto their side, but do not forcibly change any chosen position either. Avoid compressing the chest and abdomen during transport.
Cool here means avoiding overheating, rather than actively cooling an injured cat. Trauma patients can also become cold, worsening their condition. Do not use ice or cold packs to treat breathing difficulty. Follow the individual transport instructions given over the phone.
What it means for owners
A diaphragmatic hernia is dangerous and needs immediate veterinary care. Remember:
- it most often follows trauma;
- any breathing difficulty or sudden weakness after a fall or road accident warrants an urgent visit;
- timely diagnosis and surgical treatment substantially improve the chances of recovery.
This article provides information only and does not replace veterinary care. If you notice symptoms in your cat, contact a vet promptly.
Frequently asked questions
Can a diaphragmatic hernia occur without a visible wound?
Yes. A blunt impact or fall can tear the diaphragm while the skin remains intact. Altered breathing after an accident needs urgent investigation.
Does an incidental congenital diaphragmatic hernia always need emergency surgery?
Not automatically. Monitoring may be an option for symptom-free PPDH after individual assessment. Breathing difficulty, vomiting or another new symptom changes urgency.
Why is oxygen given before taking the cat straight to surgery?
Stabilising breathing and circulation improves anaesthetic safety. Timing depends on the cat's condition; rapid deterioration may require urgent repair.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Diaphragmatic Hernia, American College of Veterinary Surgeons, accessed 2026-11-03.
- Diaphragmatic Hernia in Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Diaphragmatic Hernia in Cats, Merck Veterinary Manual, accessed 2026-11-03.
- Long-term outcome of cats treated conservatively or surgically for peritoneopericardial diaphragmatic hernia: 66 cases (1987–2002), Journal of the American Veterinary Medical Association, PubMed, accessed 2026-11-03.
- Breathing problems in cats, PDSA, accessed 2026-11-03.
- Diaphragmatic Hernias in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Phase 3: Return Home, AAHA, accessed 2026-11-03.
- Initial Triage and Resuscitation of Small Animal Emergency Patients, Merck Veterinary Manual, accessed 2026-11-03.
- Care of Surgical Incisions in Cats, VCA Animal Hospitals, accessed 2026-11-03.