Todayโs path rounds is on ๐ฉ๐ฎ๐ฅ๐ฆ๐จ๐ง๐๐ซ๐ฒ ๐ญ๐ก๐ซ๐จ๐ฆ๐๐จ๐๐ฆ๐๐จ๐ฅ๐ข๐ฌ๐ฆ! This topic is related to a case I had this week.
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
A ๐ญ๐ก๐ซ๐จ๐ฆ๐๐ฎ๐ฌ is basically a giant blood clot that completely blocks blood flow through a vessel. An ๐๐ฆ๐๐จ๐ฅ๐ฎ๐ฌ is a more broad term, covering everything from smaller thrombi, bacteria, parasites or foreign material. Put them together, and you get ๐ญ๐ก๐ซ๐จ๐ฆ๐๐จ๐๐ฆ๐๐จ๐ฅ๐ข๐ฌ๐ฆ, which is a blockage of a vessel from either a thrombus or an embolus. Today, we are talking about what happens when a thrombus forms within the pulmonary veins or arteries specifically.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
All species can get this!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
There are a lot of different potential causes of pulmonary thromboembolism, but they can be broken down into two main categories: clotting issues, and stuff that shouldnโt be there. Thrombi are essentially caused by some kind of disturbance in blood clotting. In a normal blood vessel, the body works hard to maintain a balance between ๐๐จ๐๐ ๐ฎ๐ฅ๐๐ญ๐ข๐จ๐ง (blood clotting) and ๐๐ข๐๐ซ๐ข๐ง๐จ๐ฅ๐ฒ๐ฌ๐ข๐ฌ (breaking down of blood clots). When this balance is disturbed, there are two possible outcomes. Either the blood begins to clot where it shouldnโt, forming a thrombus, or you get excessive breakdown of clots, potentially leading to the animal ๐ก๐๐ฆ๐จ๐ซ๐ซ๐ก๐๐ ๐ข๐ง๐ (bleeding out or losing large amounts of blood). There are way too many diseases that can disturb this balance to describe here, but thatโs the gist of it!Emboli are basically big clumps of something that shouldnโt be in the blood stream. One example might be small pieces of a thrombus elsewhere in the body that have broken off, and flowed downstream to another blood vessel. Similarly, bacteria, tumour cells and parasites can form aggregates in the blood stream that can cause blockages. Even weird things like BB gun pellets, bullets, hair, cartilage or globs of fat can end up in the blood vessels and cause an embolus!
๐๐ก๐ฒ ๐๐ซ๐ ๐ญ๐ก๐๐ฒ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Most of the time a small thromboembolism isnโt really a big deal for the lungs. Each region of the lungs has a lot of ๐๐จ๐ฅ๐ฅ๐๐ญ๐๐ซ๐๐ฅ ๐๐ข๐ซ๐๐ฎ๐ฅ๐๐ญ๐ข๐จ๐ง, meaning they receive blood from a lot of different places, so if one of those blood pathways is obstructed, they can make up for it by getting more blood from other sources. However, sometimes you can get large thromboemboli that obstruct an entire branch of the ๐ฉ๐ฎ๐ฅ๐ฆ๐จ๐ง๐๐ซ๐ฒ ๐๐ซ๐ญ๐๐ซ๐ฒ, the major blood supply to the lungs that originates in the heart. If this artery becomes completely obstructed, suddenly the blood in the right side of the heart has nowhere to go, and the left side of the heart stops getting blood back from the lungs. This leads to severe heart dysfunction, a massive drop in blood pressure, and often sudden death.
๐๐ก๐ฒ ๐๐จ ๐ญ๐ก๐ซ๐จ๐ฆ๐๐จ๐๐ฆ๐๐จ๐ฅ๐ข ๐ ๐จ ๐ญ๐จ ๐ญ๐ก๐ ๐ฅ๐ฎ๐ง๐ ๐ฌ?
Realistically, thromboemboli can become lodged anywhere, however they are very frequently found in the lungs. The reason is all of the tiny vessels the lungs have. Once a thromboembolus enters the lungs, it goes through progressively smaller and smaller blood vessels, meaning that there is a high likelihood that eventually it will encounter a blood vessel it cannot squeeze through!
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
The clinical signs of pulmonary thromboembolism are pretty ๐ง๐จ๐ง-๐ฌ๐ฉ๐๐๐ข๐๐ข๐, meaning it can be hard to pin down whatโs going on. Sometimes, animals will have ๐๐ฒ๐ฌ๐ฉ๐ง๐๐ (difficulty breathing), ๐ญ๐๐๐ก๐ฒ๐ฉ๐ง๐๐ (increased breathing rate), coughing and lethargy. They will likely also be ๐๐ฒ๐๐ง๐จ๐ญ๐ข๐ (tissues turning blue due to lack of oxygen). However, it is quite common that animals present with sudden death, without many signs leading up to the event.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Unfortunately in animals our treatment options are pretty limited. In humans, they will try and do open heart surgery to remove the clot, or give a whopping dose of ๐ญ๐ก๐ซ๐จ๐ฆ๐๐จ๐ฅ๐ฒ๐ญ๐ข๐๐ฌ, drugs that are used to break down clots. Both of these treatments are quite risky, and overall the condition has a very high fatality rate.
๐๐ก๐จ๐ญ๐จ๐ฌ
1) A pulmonary thrombus in a dog.
2) Two pulmonary thrombi in a cat, one going into each lung.
3) A pulmonary thrombus in a cow.
4) A cross-section of a horse lung showing the arteries blocked by a thrombus.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volumes 2 and 3. Sixth Edition.
Photo 1-2 courtesy of Noahโs Arkive.
Photo 3-4 courtesy of University of Calgary Diagnostic Services Unit.
