Lipid-rich abdominal fluid mimicking chyloabdomen in a horse.

Lipid-rich fluid was found in the abdomen of an older horse with colic, initially resembling chyloabdomen, but later investigations suggested a different cause related to a fatty tumor. The horse’s condition worsened, leading to euthanasia, and post-mortem examination revealed a large fatty tumor and severe stomach inflammation.

Case Description

• A 31-year-old Arabian gelding presented with acute colic symptoms.
• Initial abdominocentesis (fluid sampling from the abdomen) produced fluid that was opaque, yellow-to-orange in color.
• The abdominal fluid showed a very high triglyceride concentration (42 g/L), significantly above the reference interval (<0.10 g/L).
• The ratio of triglycerides in the fluid compared to the serum was also elevated (11.4 vs. reference <1.0), suggesting a diagnosis similar to chyloabdomen (presence of chyle, a lymphatic fluid rich in fat, in the abdomen).

Follow-up and Clinical Course

• A second abdominocentesis performed 3 days later showed clear fluid, indicating the lipid-rich fluid was transient and the condition might mimic chyloabdomen rather than true chylous effusion.
• Despite medical treatments, the horse’s condition deteriorated, developing respiratory distress caused by pharyngeal (throat) edema.
• Due to worsening condition and poor prognosis, the horse was euthanized.

Postmortem Findings and Interpretation

• Autopsy revealed a large omental lipoma – a benign fatty tumor located on the omentum (a fold of the peritoneum covering abdominal organs).
• Severe ulcerative gastritis (inflammation with ulcers in the stomach lining) was also found.
• No abdominal effusion (fluid accumulation) was detected at necropsy, indicating the fluid seen earlier had resolved or was absent at the time of death.
• The authors speculate that necrosis (tissue death) within the large lipoma could have released lipids into the abdominal cavity resulting in the lipid-rich fluid observed.
• However, direct evidence linking the lipoma necrosis to the lipid-rich fluid was not found, so this is a hypothesis rather than a confirmed cause.

Significance of the Report

• This case highlights that lipid-rich abdominal fluid in horses does not always indicate chyloabdomen, a condition traditionally associated with lymphatic leakage.
• Other causes, such as necrotic fatty tumors, may mimic the appearance and biochemical characteristics of chylous fluid.
• Transient nature of the fluid and clinical context are important for diagnosis and management.
• This report expands understanding of differential diagnoses in horses presenting with abdominal fluid high in triglycerides.
• It also underscores the complexity of colic cases in older horses where multiple pathologies can coexist.