Effect of thoracic duct identification by CT lymphangiography and intraoperative contrast on surgical outcome in cats with idiopathic chylothorax

Objective To report the success of thoracic duct (TD) enhancement in cats with idiopathic chylothorax on preoperative computed tomography lymphangiography (CTLA) and intraoperative TD colorization (IOC), and to compare surgical outcomes between cats that did and did not have successful pre‐ and intraoperative TD enhancement. Study design Multi‐institutional retrospective study. Animals A total of 24 cats undergoing preoperative CTLA, IOC and TD ligation between February 2016 and January 2025. Methods Signalment, preoperative diagnostics, method of iohexol administration and quality of TD enhancement on CTLA, surgical procedure, success of TD enhancement via intraoperative colorization, postoperative complications, and clinical outcome were reviewed. Results TD enhancement on CTLA was successful in 70.8% of cats, with similar quality of enhancement appreciated with metatarsal and popliteal iohexol injection. TD colorization with indocyanine green (ICG) seen via near‐infrared fluorescence (NIRF) was successful in four of five (80%) cats, while methylene blue was successful in eight of 15 (53%) cats. When both TD enhancement on CTLA and IOC occurred, clinical resolution rates were highest (77%) and significantly longer survival times were observed ( p = .002), compared to when either CTLA or IOC (53%) or neither (25%) was successful. Conclusion Successful enhancement of the TD via CTLA and IOC led to higher clinical resolution rates and was associated with longer survival compared to when only one or neither modality was successful. Clinical significance The success of TD enhancement via CTLA and IOC may have prognostic significance for cats with idiopathic chylothorax.