Pulmonary Thromboembolism in Donkeys: Clots Affecting the Lungs

Pulmonary thromboembolism means a blood clot, or material associated with a clot, travels through the bloodstream and lodges in blood vessels inside the lungs. That blockage reduces normal blood flow and oxygen exchange. In a donkey, this can lead to sudden respiratory distress, low blood oxygen, strain on the heart, and sometimes rapid collapse.

Although donkey-specific research is limited, vets generally manage this condition using equine principles because donkeys and horses share similar cardiopulmonary anatomy and clotting risks. In equids, pulmonary thromboembolism is usually secondary to another serious problem, such as systemic infection, endotoxemia, severe inflammation, or thrombophlebitis associated with an IV catheter or repeated jugular injections.

Some clots are sterile, while others are septic, meaning they carry bacteria and can seed infection into the lungs. That distinction matters because treatment may need to address both the clotting problem and the underlying infection. Even with prompt care, prognosis can be guarded because the donkey is often dealing with more than one major illness at the same time.

In donkeys, pulmonary thromboembolism is most often the result of another disease process that makes clot formation more likely. Important risk factors in equids include severe infection, endotoxemia, systemic inflammation, dehydration, prolonged recumbency, and vascular injury. Jugular thrombophlebitis is a well-recognized equine problem after IV catheterization or repeated injections, and clots from affected veins may contribute to embolic complications.

Septic clots are especially concerning. These can form when bacteria enter the bloodstream or a damaged vein and then travel to the lungs, where they block vessels and may also trigger embolic pneumonia or abscess formation. In large animals, liver abscesses with vena caval thrombosis are a classic cause of septic pulmonary emboli in cattle, and similar lesions have been reported in at least one horse, showing that this pathway can occur in equids too.

Other possible contributors include severe gastrointestinal disease, laminitis-associated systemic inflammation, post-surgical hypercoagulability, neoplasia, and less commonly inherited or acquired clotting abnormalities. Because donkeys often mask illness until they are quite sick, the underlying trigger may already be advanced by the time breathing signs appear.

Diagnosis starts with an emergency physical exam. Your vet will assess breathing effort, heart rate, gum color, temperature, and oxygenation, then look for clues to the underlying cause. Bloodwork may include a CBC, chemistry panel, fibrinogen or serum amyloid A, coagulation testing, and sometimes blood-gas analysis to check how well oxygen is moving into the bloodstream.

Imaging and targeted exams are often needed. Thoracic ultrasound can help identify pleural fluid, peripheral lung consolidation, or other competing causes of respiratory distress. Ultrasound of the jugular veins is especially useful if there is neck swelling, pain, or a recent catheter history. Chest radiographs may be possible in some settings, but they can be logistically difficult in adult equids and may not confirm the diagnosis.

A definitive diagnosis of pulmonary thromboembolism can be challenging in veterinary patients, including equids. Vets often make a presumptive diagnosis based on sudden respiratory signs plus evidence of thrombosis, sepsis, or hypercoagulability elsewhere in the body. In referral settings, repeated ultrasound, arterial blood-gas monitoring, echocardiography, and advanced supportive monitoring may help guide treatment even when the clot itself cannot be directly imaged.

Not every case can be prevented, because pulmonary thromboembolism is usually a complication of another serious illness. Prevention focuses on reducing clot risk and catching the underlying problem early. Prompt treatment of sepsis, colitis, endotoxemia, severe respiratory infections, and inflammatory disease matters. Good hydration, careful nursing care, and early reassessment of any donkey that becomes dull or stops eating can also help.

Catheter and vein care are especially important in equids. If your donkey needs IV treatment, your vet will aim to minimize jugular trauma, monitor for swelling or pain, and remove or replace catheters when needed. Tell your vet quickly if you notice heat, firmness, discharge, or swelling along the neck after injections or catheter use.

For donkeys recovering from major illness or surgery, follow discharge instructions closely and keep recheck visits. Some high-risk patients may need closer monitoring for clotting complications, but the right plan depends on the whole case. The best prevention strategy is an early partnership with your vet when your donkey first seems unwell, rather than waiting for breathing distress to appear.