Water in the lung what does it mean exactly veterinary medicine simplified

Water in the lungs – What does it mean exactly??Water in the lungs – one hears it again and again – but what does it actually mean exactly and what is behind it? Fluid in the lungs is life threatening. Can lead to suffocation if left untreated. One must distinguish between fluid accumulation in the lungs (pulmonary edema). Distinguish in the chest (thoracic effusion). Both cause dyspnea, but cause and treatment are usually different. I would like to focus on the problem of "water in the lungs". Will only briefly write about thoracic effusion in the last paragraph.

Water in the lungs – pulmonary edema

Possible causes¹:

Heart failure
– Toxins (z.B. Smoke gas) – Medications – Iatrogenic (over-infusion) – Protein deficiency – Infections – Electrical shock, seizures, head trauma – Blocked airways (z.B. by foreign bodies) – "inhalation" of fluid (z.B. under anesthesia, under water) – lack of oxygen (altitude sickness)

Heart failure is the most common cause of pulmonary edema. Other causes are less common, usually occur late in the course of other diseases, and often have a different clinical picture and other symptoms.

Symptoms of water in the lungs:

– Respiratory distress – Increased resting respiratory rate – Cough (>heart cough dog, heart cough cat) – Abdominal breathing – Mouth breathing (cat) – Blue mucous membranes – Restlessness

Water accumulation decreases the volume of the lungs available for oxygen exchange and therefore breathing becomes faster. This increases to a high degree of shortness of breath. This is initially recognized by an increased resting respiratory rate (>40 breaths/minute at rest), increased abdominal breathing and panting. Dogs cough more, cats cough only rarely. Due to the lack of oxygen. The respiratory distress is restless. When the oxygen supply is insufficient, the mucous membranes may appear bluish (you can see it, for example, when you lift the lips and look at the gums).

In cats, this bad condition often appears very quickly, as they are masters at hiding illnesses. Panting in particular is rarely normal in cats. Should be taken very seriously. Dogs are more likely to show earlier signs such as coughing, less appetite and listlessness, but can also have a very rapid acute course.

Diagnosis of pulmonary edema¹

Patients with fluid in the lungs usually come to the practice with respiratory distress. This means the animal should be stressed as little as possible and haste is needed to start the right therapy. To diagnose pulmonary edema, an x-ray is taken. This must be done as soon as possible. Stress free as possible. In some situations, even an x-ray is too much stress, especially in cats, and oxygen must be given first to stabilize the patient. If possible in an oxygen box. As soon as the animal has calmed down a bit, the x-ray should be taken and appropriate therapy should be started. Heart problems are the most common causes of pulmonary edema, other possible causes are much rarer, which is why I will only discuss the heart problem below. A cardiac ultrasound will reveal if. Which heart problem is present. However, ultrasound cannot be used to evaluate the lungs, because air completely reflects ultrasound waves. A cardiac ultrasound should follow as soon as the animal is stabilized. In cats, it is now possible to do a rapid biomarker test to confirm or rule out a cardiac cause for the dyspnea. The rapid test is not a substitute for an ultrasound, but it can be used very well when quick decisions are needed and there is no cardiologist on site.

What happens in heart failure

Heart failure means that a heart disease has progressed to the point where the heart or the body can no longer pump the entire volume of blood through the body by means of various compensatory mechanisms. Heart disease has usually been present for a long time, but has not caused any clear symptoms up to this point.

What exactly happens:

In healthy cardiopulmonary circulation, blood is pumped from the right side of the heart to the lungs, where carbon dioxide is offloaded and oxygen is recharged. The blood then flows to the left side of the heart and is pumped by the strong left heart muscle into the aorta and thus into the systemic circulation. Gas exchange takes place in the alveoli of the lungs. There the vessels enclose the air-filled small air sacs.

Now, with heart disease, there may not be enough blood being pumped into the systemic circulation. This is called left heart failure. A failure of the left side of the heart is the case in very many heart diseases, such as.B. Mitral valve endocardiosis, hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and some congenital heart diseases. As a result, the left atrium expands to accommodate the blood that is not being pumped onward. In addition, the body starts to increase the blood volume, because less is reaching the body and it thinks it has to compensate for this. This makes the situation in the heart even worse. The atrium becomes even larger. At this stage, however, the patient does not yet show any symptoms, gas exchange in the lungs is not impaired. Eventually, the dog may cough as the enlarged heart presses on the large bronchi. At some point the capacity of the atria is exhausted. It cannot expand any further. The blood now backs up further into the pulmonary vessels. Like a traffic jam on the highway that gets longer and longer. The pulmonary vessels can also only withstand a certain amount of prere until fluid eventually leaks through the thin vascular wall around the alveoli. The sacs fill with more and more fluid and pulmonary edema forms. Filled alveoli are no longer available for gas exchange and respiratory distress occurs.

Treatment for water in the lungs

The primary treatment goal is to remove the fluid from the lungs as quickly as possible. This makes it easier for the animal to breathe and prevents it from suffocating. You can't just drain the fluid because it's in the ties or in the very small alveoli. Therefore, the fluid is reduced by means of drainage drugs (furosemide, torasemide). Thus, an attempt is made to dry out the body so that the water can be reabsorbed into the vessels. Drainage medications are very effective, but often need to be given in very high doses initially to get through the acute phase. If you catch pulmonary edema in the early stages, you have to treat it less aggressively. Once the patient is stable enough, they will try to go down a bit with the dehydration and find the lowest possible dose. However, this must be done over a period of days. Depending on the underlying disease, additional medications will be needed ².

Who wants to read more about cardiac therapy:

The patient must remain hospitalized

It depends on what condition the animal is in, whether hospitalization is appropriate or not. In the case of very severe respiratory distress, dehydration should be given directly into the vein (hourly or even in a continuous drip) and oxygen should be supplied – an inpatient stay, especially the critical first 24 hours, is therefore advisable and promises greater success than outpatient therapy.

What happens next

Once the patient has passed the first phase, the medications are adjusted to provide a good quality of life for the animal. Unfortunately, constant drainage is usually no longer possible in this case. The goal is a balance between new water in the lungs. Finding drainage through medication. Here, above all, the owner must recognize when the drainage is no longer sufficient and the dose must be increased or perhaps another drug must be added to it. For this, the resting respiratory rate should be counted regularly at home.

Resting respiratory rate count:

When the animal is asleep or lying still, count how many times a minute the chest rises and falls again. The value should be. cat should be below 40 breaths per minute ³. The first sign of water in the lungs is an increasing respiratory rate. If you do this regularly, you will get a good feel for what is "normal" in your pet and thus notice more quickly if something is wrong and can react accordingly. The faster you react, the higher the chance of successful therapy.


Most – unfortunately not all – animals with acute respiratory distress due to heart failure can be re-stabilized with appropriate therapy. The first 12 to 48 hours are important. However, the earlier the treatment, the better the chances of recovery. Unfortunately, there are also animals that can no longer be stabilized and for which euthanasia is appropriate after a certain period of time without improvement.

Once the initial phase is over, it is important to get the animal well adjusted and to adjust the therapy whenever necessary. For the most common cardiac diseases, the average survival time is approx. one year after water on the lungs was first detected 4.5 . This time can be much shorter but also much longer. It is important to know that the quality of life during this time is usually very good and it is therefore recommended in any case to start a therapy attempt. More about the life expectancy of cats with HCM. Dogs with an enlarged heart can be seen in separate articles.

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Fluid accumulation in the chest

Possible causes:

– Heart problem (right heart failure, pericardial effusion, heartworms, in cats also left heart failure) – Tumor – Liver problem – Infection (z.B. FIP, leishmaniasis) – bleeding (z.B. after an accident) – protein deficiency

Difference with fluid in the lungs:

There is a gap between the inner chest wall and the lungs, which usually contains minimal fluid. Otherwise both are close to each other. In this gap can be z.B. Heart failure more. Collect more fluid. This fluid can be easily visualized on ultrasound because it is outside the lung tie. In case of water in the lungs, it is located in the lung tie and the small pulmonary alveoli. As an example, one can imagine a sponge stuck in a plastic bag. Both are now placed in a glass. The glass represents the chest, the bag the skin around the lungs and the sponge the lungs. If the sponge is soaked with liquid, this corresponds to pulmonary edema. On the other hand, if the glass is precipitated with water, this simulates a thoracic effusion.

Peculiarity in cats:

Water in the lungs in cats often occurs simultaneously with a thoracic effusion. It is not fully understood what exactly determines whether only pulmonary edema, only thoracic effusion, or both develop when the heart fails. However, the occurrence of a thoracic effusion is often associated with a worse prognosis 6 .


The therapy depends on the cause. In many cases it makes sense to aspirate the fluid to give the patient a first relief in breathing. The puncture of the thorax is thereby without much effort and without anesthesia feasible. However, the root cause is not corrected in the process. However, time is gained to start further therapies or to make decisions. In the case of heart failure, the animal usually needs permanent drainage medication, as in the case of pulmonary edema.

Here is an extra case report and article about water in the stomach

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