Pleural effusion in feline congestive heart failure
8-year-old Ragdoll cat with hypertrophic cardiomyopathy, a markedly dilated left atrium and no signs of right-sided failure. It has moderate bilateral pleural effusion with rapid, shallow breathing.
Which statement is correct?
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A. In cats pleural effusion only appears with right-sided heart failure, so another cause must be sought
In cats the visceral pleura partly drains into the pulmonary veins, so left-sided failure alone can produce pleural effusion; it is a very common presentation.
B. High-dose furosemide is enough; thoracocentesis should be avoided because of stress in the cardiac cat
Diuretics resorb pleural effusion slowly; with moderate or severe effusion, thoracocentesis relieves dyspnoea immediately and is the treatment of choice, with minimal restraint.
C. Left-sided failure can cause pleural effusion in cats; drain it by thoracocentesis and start a diuretic. The fluid is usually a modified transudate, although it can be chylous
Correct. Raised pulmonary venous pressure impairs drainage of the visceral pleura. Thoracocentesis resolves the dyspnoea and furosemide prevents reaccumulation. Feline cardiogenic effusion can be chylous: that is why heart disease must be ruled out in every cat with chylothorax.
D. If the fluid is chylous, a cardiac cause is ruled out and it should be treated as idiopathic chylothorax
Heart failure is one of the causes of chylothorax in cats; treating a cardiac cat as idiopathic would deprive it of effective treatment.
lightbulb Key takeaway
After drainage, repeat the ultrasound: the fluid no longer masks the left atrium or oedema. Teach the owner to count the resting respiratory rate. If effusion reaccumulates despite treatment, review the diuretic dose and consider adding other drugs according to the ACVIM consensus on feline cardiomyopathies.
References: ACVIM consensus statement guidelines for the classification, diagnosis and management of cardiomyopathies in cats (2020)
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.