What are arteriovenous fistulas and arteriovenous malformations?

Arteriovenous fistulas and arteriovenous malformations are abnormal connections between blood vessels that may be developmental or acquired. They allow arterial blood to flow directly into veins, changing local or whole-body circulation and potentially affecting heart workload or organ function. Diagnosis usually requires imaging confirmation, so consult your vet.

How do vets diagnose these vascular abnormalities?

Diagnosis usually combines a physical examination with imaging such as chest and abdominal ultrasound, echocardiography, CT, or MRI. Angiography may be used when needed to confirm the direction of blood flow. Blood tests can assess organ function and check for complications such as anaemia or infection.

What treatment options are available?

Treatment depends on the location and severity of the lesion. Common options include interventional vascular embolisation or surgical repair, along with medication and supportive care when needed. Whether surgery is appropriate requires specialist review of imaging and your pet's overall health, so discuss this with your vet.

How long is follow-up needed after surgery or conservative treatment?

Follow-up frequency varies by case. After surgery, pets often return within weeks to months for repeat imaging and blood tests. Long term, rechecks may be needed every 3-6 months to assess recovery, heart strain, and recurrence risk. Follow your vet's recommended schedule.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

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Disease Guide

Arteriovenous Fistula and Malformation in Dogs and Cats: Coughing, Imaging & Follow-up Care [2025]

An arteriovenous fistula is an abnormal connection between blood vessels that can overload the heart and may require surgical correction in severe cases.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap Editorial Team

Sources: ACVIM, AAHA, National Taiwan University Veterinary Teaching Hospital

When to See a Vet

Seek immediate emergency care

•Difficulty breathing with open-mouth breathing or gasping
•Purple or bluish gums and lips with noticeably reduced responsiveness
•Sudden collapse or prolonged loss of consciousness

Schedule a clinic visit promptly (within 24–72 hours)

•Persistent coughing that worsens at night or during activity
•Noticeably rapid breathing after activity that improves with rest
•Intermittent seizures or localized weakness causing limping

01What symptoms suggest something is wrong?

Arteriovenous abnormalities can affect the heart, lungs, or local blood flow, often causing coughing, breathing changes, or localised swelling. A vet should assess the cause and severity.

Persistent or recurring coughing, especially at rest or at night
Faster or shallow breathing that worsens after activity
Seizures or other abnormal neurological behaviours
Abdominal swelling or fluid build-up in the abdomen
Swelling in the limbs or a localised body area, or intermittent limping

Seek emergency care immediately if you notice the following symptoms:

⚠️ Difficulty breathing, open-mouth breathing, or blue-purple lips or gums
⚠️ Sudden collapse or loss of consciousness
⚠️ Ongoing seizures that do not stop

02How can you assess abnormalities at home? Key observations and emergency warning signs

Keeping notes and videos of key changes at home helps your vet understand the condition quickly, prioritise tests, and decide when treatment is needed.

Record how often coughing occurs and when episodes happen, such as at night or after activity
Use your phone to record videos of breathing, walking, or seizure-like episodes to show the vet
Note whether appetite, water intake, or activity levels have decreased
Record changes in urination or bowel movements, including frequency, colour, and timing
Watch your pet's walking posture and note which leg or body area appears lame
If symptoms worsen, arrange a vet appointment or emergency assessment as soon as possible

03How will the vet diagnose it? Common tests

Vets use a physical examination together with imaging and blood tests to locate the vascular abnormality, assess heart and lung strain, and check for complications affecting other organs.

Physical examination

auscultation, palpation, and a basic neurological assessment

Chest and abdominal ultrasound to assess heart strain and fluid accumulation

Echocardiography to check heart structure and function

CT or MRI to evaluate the extent of the vascular malformation and its relationship with nearby tissues

Blood tests to assess organ function, anaemia, or markers of infection

Referral to a specialist hospital with echocardiography and advanced imaging is recommended

04How is it treated and managed after diagnosis? Medication, diet changes, and care guide

Treatment may involve interventional or surgical procedures, medication, and long-term monitoring. Whether treatment is surgical or conservative, regular rechecks and imaging are important.

Surgical or interventional treatment to repair or block the abnormal blood vessel connection
Medication may be used to manage heart strain and related signs, as determined by your vet
Diet and weight management to reduce strain on the heart, lungs, and body
Regular follow-up visits after surgery or conservative treatment, including repeat imaging and blood tests
Home care may include restricted activity, wound monitoring, and watching for symptom changes
Long-term follow-up with a cardiology or vascular specialist is recommended

05What should you prepare before seeing the vet? Key details that help identify the cause

Bring a written or phone record of symptoms and when they started

Prepare videos on your phone showing coughing, breathing, or walking changes

List your pet's usual diet, water intake, and toileting records for reference

Bring a list of all current medications and supplements for the vet to review

If you have previous imaging or reports, bring them to the appointment

Consider booking directly with a specialist service that can perform echocardiography or advanced imaging

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.

Related Symptoms (You May Also Be Looking For)

Ascites

Abdominal fluid

Cough

Forceful air expulsion from airways

Edema

Tissue swelling

Exercise Intolerance

Reduced exercise capacity

Heart Murmur

Abnormal heart sound

Lameness

Limping