Neil McIntosh gives a reader advice on his coughing dog.
This is a very good question but unfortunately not one that can be answered easily. I certainly appreciate your candour, because an honest, genuine history is an important part of the diagnosis in any coughing dog. It is worth stating that the results of a four year study at the Animal Medical Centre of Nihon University, Kanagawa, Japan, showed that passive tobacco smoke exposure (PTSE) made virtually every canine respiratory condition worse. While it is likely that PTSE actually causes damage, it is very clear that it exacerbates pre-existing lung and heart problems. As far as your girl is concerned, we would need to differentiate between the common causes of coughing in older dogs. Obviously, most youngsters present with infectious coughs but geriatrics can be affected by lung and heart problems.
We can diagnose this when there has been coughing on most days over a two month period. A variety of causes, including
PTSE, previous respiratory infections and pure bad luck conspire to cause chronic inflammation of the airways, leading to increased mucus production and poor performance of the cilia (the little hairs that constantly waft mucus out of the lungs). As a result, the tiny airways, called bronchioles, become plugged and thicken.
“Older dogs can be affected by lung and heart problems... or both!”
Dogs are usually bright but there is a chronic cough (with occasional production of white froth) and exercise tolerance is poor. Sometimes wheezing or crackling can be heard. Steroids, antibiotics and bronchodilators can help, but care should be used with anti-cough medicine because this can cause a dangerous build-up of mucus in the airways. I prefer to only use it at night to allow rest. Remember there are many other lungs diseases caused by (for example) allergy, parasites and tumour. But this is a magazine article, not a book.
A very complicated subject but some basic information allows understanding and what to look out for! The heart is a pump, consisting of four chambers; the right atrium and ventricle and the left atrium and ventricle. The atria and ventricles are separated by the mitral valve on the left side and the tricuspid valve on the
right. These valves stop the backflow of blood. The right side of the heart pumps deoxygenated blood that has returned from the body through the pulmonary artery into the lungs, where it is oxygenated (if the lungs are functioning properly). The oxygenated blood then returns to the left atrium before being pumped by the left ventricle to the body. Most commonly in older dogs, heart disease occurs as a result of valve or cardiac muscle problems.
Left-sided heart failure
Damage to the mitral valve allows backflow of blood from the left ventricle to the atrium and consequent poor tissue perfusion initiating a change of events that at first helps maintain blood pressure but ultimately causes more damage. Fluid retention in the lungs is the result.
Signs to look out for:
• Increased respiratory rate (tachypnoea) • Difficulty breathing (dyspnoea)
• Exercise intolerance • Collapsing/Fainting
• Increased heart rate (Tachycardia)
Right-sided heart failure
Less often, the tricuspid valve is affected. (Although Labradors can have malformation of the valve; a condition called tricuspid valve dysplasia, which causes a murmur to be audible high up on the right side of the chest. Puppies should be checked for this.) In right-sided failure, fluid builds up in the abdomen and the liver is enlarged.
Signs to look out for:
• Abdominal distension
• Exercise intolerance
• Weight loss
Heart muscle damage
This generally affects large and giant breeds and is called Dilated Cardiomyopathy. Essentially, the muscle becomes flabby and useless as a pump. Unfortunately, prognosis is poor.
If your old dog is coughing, have a heart and take them for a check-up…
Chest X-rays are useful in the diagnosis of heart and lung problems
Smoke exposure Tobacco smoke exposure exacerbates pre-exisiting lung and heart problems