Determining agreement between preoperative computed tomography lymphography and indocyanine green near infrared fluorescence intraoperative imaging for sentinel lymph node mapping in dogs with oral tumours.

Lymphatic drainage from the head and neck is variable with significant crossover, therefore sentinel lymph node (SLN) mapping can help ensure the appropriate lymph node(s) are sampled. To improve sensitivity, SLN mapping utilizing multiple modalities and a combination of preoperative computed tomography lymphography (CTL) and intraoperative near infrared fluorescence imaging (NIRF) with indocyanine green (ICG) +/- methylene blue (MB) dye has been suggested. The aim of this study was to describe a method for intraoperative ICG lymphography and determine agreement for SLN detection using preoperative CTL and intraoperative ICG NIRF + MB lymphography (IOL) in dogs with oral tumours. Fourteen client-owned dogs were included. All dogs had preoperative CTL with iodinated contrast and intraoperative IOL with an exoscope. Lymph nodes with CTL contrast-enhancement, blue staining or fluorescence were considered sentinel. The overall SLN identification rate was 100% when CTL and IOL were combined. A total of 57 SLNs were identified. Indocyanine green NIRF identified a greater proportion of SLNs (91%; 52/57) compared with MB (50.8%; 29/57) and CTL (42.1%; 24/57). Eighteen SLNs were identified by all three modalities with a fair level of agreement using Fleiss kappa. These findings suggest a combination of preoperative CTL with intraoperative SLN mapping techniques may greatly improve the ability to accurately detect the SLN in dogs with oral tumours.