Constrictive physiology is not present in all dogs with idiopathic chylothorax.

Objective: To determine whether subtotal pericardectomy affects recurrence and long-term outcomes in dogs with idiopathic chylothorax (IC).

Animals: 12 client-owned dogs diagnosed with IC between July 26, 2016, and March 23, 2023.

Methods: The diagnosis of constrictive physiology (CP) was established with cardiac catheterization and defined as elevated and equal diastolic pressures in all 4 cardiac chambers. Dogs were then entered into the constrictive physiology (CP) group or non-CP (NCP) group. All dogs received at least a thoracic duct ligation (TDL). The dogs in the CP group had a subtotal pericardectomy performed in addition to TDL. Repeated surgical interventions, recurrence, long-term outcomes, and survival times were recorded.

Results: 8 dogs were entered into the CP group and underwent TDL and subtotal pericardectomy. Four dogs were entered in the NCP group and underwent only a TDL. Four dogs in the CP group and 1 in the NCP group required multiple surgeries for recurrent chylothorax. The 1-, 2-, and 3-year disease-free rates were, respectively, 100%, 100%, and 50% for the NCP group and 87.5%, 72.9%, and 72.9% for the CP group (P = .935). The 1-, 2-, and 3-year survival rates were, respectively, 100%, 100%, and 100% for the NCP group and 87.5%, 72.9%, and 72.9% for the CP group (P = .317).

Clinical Relevance: Constrictive physiology should be evaluated by cardiac catheterization before surgical treatment of IC in dogs. If CP is not diagnosed, subtotal pericardectomy may not be required.