Peer-reviewed veterinary case report
Causes of fluid buildup in dogs and cats - what to know
By Sotillo, Samantha et al.·Published in Journal of veterinary internal medicine·2025·Department of Veterinary Clinical Sciences, United States·View original on PubMed →
PetCaseFinder translated the abstract of this peer-reviewed paper into plain English so pet owners can read it. We do not publish original research — every detail traces back to the citation above. How we work →
Original publication title: Retrospective Evaluation of the Causes and Fluid Characteristics of Cavitary Effusions in Dogs and Cats.
Plain-English summary
This study looked at the reasons behind fluid buildup in the body cavities of dogs and cats, analyzing samples from 269 dogs and 107 cats. In dogs, the most common cause of fluid in the abdomen was low protein levels in the blood, while fluid in the chest was often due to low protein or cancer. In cats, the reasons for fluid buildup were less clear, with many cases showing similar characteristics regardless of the cause. Overall, the findings suggest that understanding the type of fluid can help identify the problem in dogs, but it's not as straightforward for cats.
Abstract
BACKGROUND: The relationship between fluid characteristics and cause of cavitary effusions is incompletely characterized. HYPOTHESIS/OBJECTIVES: Describe fluid characteristics and cytologic classification of cavitary effusions in dogs and cats. ANIMALS: A total of 269 dogs and 107 cats with cytologic fluid analysis of cavitary effusion. METHODS: Retrospective medical record review (2016-2020). Differences among groups were assessed using Kruskal-Wallis testing with post hoc pairwise Dunn's or Fisher's Exact testing. RESULTS: In dogs, peritoneal transudates most frequently were caused by decreased oncotic pressure (DOP; 63%, p < 0.001) and modified transudates by increased hydrostatic pressure (IHP; 41%, p < 0.001). Peritoneal exudates more frequently were caused by increased vascular permeability (IVP; 40%), ruptured viscera (35%), or neoplasia (23%) compared with IHP or DOP (p < 0.01 for all). Pleural transudates in dogs most frequently were caused by DOP (79%, p < 0.001) and modified transudates by IHP (33%) or neoplasia (29%). Pleural exudates were more likely to be caused by neoplasia (52%) or IVP (36%) compared with IHP or DOP (p < 0.001). In cats, peritoneal effusions commonly were caused by IVP or neoplasia, and pleural effusions by IHP or neoplasia. No statistical relationship was found between cytologic category and cause of effusion in cats. CONCLUSIONS AND CLINICAL IMPORTANCE: Cytologic classification and fluid characteristics are most predictive of disease process in peritoneal effusions in dogs, whereas effusions in cats have substantial overlap across causes.
Find similar cases for your pet
PetCaseFinder finds other peer-reviewed reports of pets with the same symptoms, plus a plain-English summary of what was tried across them.
Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/40757981/