Diaphragmatic Hernia in Dogs and Cats: Signs, Surgery and Recovery

By Dr Duncan Houston

After a road accident, fall or major impact, a pet may have internal injuries even when the skin looks normal. A diaphragmatic hernia is one possibility and can make breathing difficult.

Some hernias are present from birth and are discovered incidentally. These cases need a different discussion from an acutely injured animal struggling for air.

Quick Answer

A diaphragmatic hernia allows abdominal organs to move through an abnormal opening in the muscle separating abdomen and chest. Traumatic cases generally require stabilisation and surgical repair, with timing based on breathing, circulation and the organs involved. Selected congenital cases need individual assessment of surgery versus monitoring. Breathing distress or collapse is an emergency.

What types occur?

Trauma can tear the diaphragm, allowing organs such as liver, intestine or stomach into the chest. This crowds the lungs and may compromise an organ’s blood supply.

A congenital peritoneopericardial diaphragmatic hernia, or PPDH, involves an abnormal connection with the sac around the heart. It is not the same as an ordinary traumatic tear. The American College of Veterinary Surgeons’ hernia guidance explains these differences and treatment planning.

What signs can it cause?

Signs include fast or difficult breathing, reduced exercise tolerance, poor appetite and sometimes vomiting or abdominal discomfort. Some chronic or congenital hernias cause few obvious signs until found on imaging.

After an accident, other injuries such as lung bruising, bleeding or fractures may be more immediately apparent. A dog or cat walking away from an impact is not proof that the chest is uninjured.

How is it diagnosed?

Chest radiographs may show displaced organs or an abnormal diaphragm outline. Ultrasound can add information, and CT is sometimes useful in complex cases. The safest order of testing depends on the animal’s stability.

The Merck review of diaphragmatic hernia describes the importance of respiratory and circulatory assessment. Severely distressed patients may need oxygen and minimal handling before detailed imaging.

What else can cause the same breathing pattern?

Pneumothorax, fluid or blood around the lungs, pneumonia and heart failure can look similar. Several may coexist after trauma. A quiet chest on examination or a fast breathing rate cannot identify the cause alone.

What happens during surgery?

The surgeon returns displaced organs to the abdomen, evaluates their condition and closes the defect. Anaesthesia requires careful ventilation and monitoring because normal breathing mechanics are disrupted. Damaged tissue or other injuries may require additional treatment.

Stabilisation before surgery is often important, but a trapped or compromised organ can make urgent intervention necessary. There is no universal waiting period suitable for every patient. The team balances the risk of operating now against the risk of delay.

For an incidentally found congenital hernia, the decision includes signs, organs involved, progression risk and anaesthetic considerations. Monitoring should be an explicit plan, not an assumption that a quiet hernia can never cause trouble.

When is this an emergency?

Go immediately for breathing effort, blue-grey gums, collapse, severe pain or repeated unproductive retching. Keep the pet quiet and allow its preferred breathing posture. Do not compress the chest or abdomen, force-feed or give human painkillers. Call ahead so the clinic can prepare.

Recovery at home

1. Follow the surgeon’s activity restrictions, including limits on jumping and stairs.
2. Give medicines exactly as prescribed and keep the wound protected from licking.
3. Monitor resting breathing, appetite, vomiting and energy.
4. Check the incision gently without pressing on the abdomen.
5. Attend the planned recheck before returning to normal activity.
6. Return urgently if breathing worsens, pain increases or your pet becomes weak.

Recovery time depends on the original injury and surgery. A pet with multiple injuries may need a longer or more complex plan than one undergoing an uncomplicated congenital repair.

Common mistakes

• Assuming a normal-looking chest means no internal injury.
• Delaying care because the accident happened several days earlier.
• Comparing a congenital case with a severely injured trauma patient.
• Restarting rough play because the skin incision looks healed.

Prevention

Road safety, secure windows and balconies, appropriate restraints and preventing fights reduce traumatic risk. Congenital defects cannot be prevented through ordinary home care. Discuss breeding implications and any associated abnormalities with your vet.

Frequently asked questions

Can a diaphragmatic hernia appear long after an accident?

It may be recognised later if the original injury was missed or signs were subtle.

Does every case need immediate surgery?

No. Timing depends on stability and organ compromise, but breathing distress needs immediate assessment.

Can pets recover well?

Many do, especially when other injuries are limited and repair is successful. Prognosis remains individual.

The safest decisions come from understanding the hernia type, current breathing and condition of the displaced organs.

For help understanding your animal’s care and preparing questions for your veterinarian, visit ASK A VET™. Seek in-person emergency care immediately for urgent signs.