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Objective: To evaluate the feasibility of CT lymphangiography via intrametatarsal pad injection in cats with chylothorax., Animals: 7 client-owned cats., Procedures: This was a multicenter, retrospective, descriptive study. Medical records and imaging data from 4 veterinary hospitals were reviewed to identify cats with chylothorax that had undergone intrametatarsal pad injection via CT lymphangiography. In total, 7 client-owned cats were included in the study. Signalment, history, image findings, and follow-up data were recorded. Descriptive statistics were used to analyze the success rate of thoracic duct (TD) enhancement and describe relevant clinical findings., Results: Enhancement of TDs was successful in 6 of the 7 cats within 5 to 15 minutes after initiating intrametatarsal pad injection under general anesthesia. Successful migration of contrast medium into the lymphatic vessels cranial to the popliteal lymph nodes was observed in all cats within 5 minutes after injection. The recommended dose of contrast medium to achieve TD enhancement was 1 mL/kg (0.5 mL/kg/pad; concentration, 350 mg of iodine/kg). Only 1 cat had mild swelling of the paws after the procedure, and it recovered quickly without pain medication; no cats experienced lameness. Similar to dogs and unlike in previously published reports, 72% of TD branches were located in the right hemithorax., Clinical Relevance: CT lymphangiography via intrametatarsal pad injection is a feasible and safe procedure for cats with chylothorax. This technique provides detailed information regarding the unique TD anatomy and cisterna chyli location. It also contributes to surgical planning.

Lymphangiography can be useful for preoperative planning in chylothorax. Conventional ultrasound-guided intranodal injection can be difficult in some cases and is dependent upon operator skill. Alternative methods have been proposed to simplify the procedure, but their feasibility has not been sufficiently evaluated in clinical cases. The primary purpose of this multicenter, retrospective, descriptive study was to assess the feasibility and describe the clinical findings of CT lymphangiography by intrametatarsal pad injection in dogs with naturally occurring chylothorax. Twenty dogs were analyzed, and enhancement of thoracic ducts (TDs) was successful in 18 (90%) dogs within 5-14 min after initiating the injection, while successful enhancement of the lymphatic vessels cranial to the popliteal lymph nodes was seen in all dogs within 5 min after injection. The dose with good success to achieve TD enhancement was 1 mL/kg (concentration 350 mg I/kg). Only two dogs had mild discomfort after recovery from general anesthesia. Computed tomography lymphangiography by intrametatarsal pad injection is a feasible, easy, and safe procedure, which could provide adequate TD and cisterna chyli enhancement, identify TD number and cisterna chyli location and structure, and contribute to surgical planning., (© 2020 National Marine Mammal Foundation. Veterinary Radiology & Ultrasound published by Wiley Periodicals, Inc. on behalf of American College of Veterinary Radiology.)