Peripheral sentinel lymphadenectomyn in 163 dogs: complication rate and comparison between intraoperative unguided and guided techniques

Objectives: This retrospective study aimed to describe the incidence rate and the severity of the complications following peripheral lymphadenectomy in dogs, comparing three different guiding techniques: intraoperative γ-probing and methylene blue dye (MB), MB only, and unguided lymphadenectomies. The second aim was to investigate whether the number, being palpable, and site of sentinel lymph node (SLN) influenced the incidence of complications. Methods: Client-owned tumour-bearing dogs undergoing both pre-operative SLN mapping and excision of peripheral SLNs were included. Type of pre- and intraoperative mapping technique used, number of excised SLNs and being palpable, postoperative treatments, number, type, and timing of complications observed were collected. Complications were defined according to LeBlanc et al. (2021). Results: A total of 201 peripheral lymphadenectomies from 163 dogs were enrolled. Seventy-two (59%) lymphadenectomies were performed without intraoperative guidance, 49 (41%) with MB, and 80 (40%) with γ-probe and MB. The overall incidence of complications reported was 7.5% (15/201), and 80% (12/15) of them were mild. In the logistic regression model, the use of intraoperative guidance and any of the factors considered did not significantly influence the complication rate. The most frequent postoperative event was seroma (2.5%). Using the decision tree model, mandibular and retropharyngeal lymphadenectomy significantly affected the complication rate, especially when surgery lasted more than 21.5 minutes. Conclusions: Lymphadenectomy of peripheral SLNs was associated with a low rate of self-limiting mild complications, which is not affected by the type of intraoperative guidance; mandibular and retropharyngeal lymphadenectomies that lasted more than 21.5 minutes may result in more complications.