The use of methylene blue to assist with parotid sialadenectomy in dogs

Abstract

There is an important morbidity associated with parotidectomy. The most commonly reported permanent complication is facial nerve injury. Methylene blue staining has been used as an intra-operative tool to improve tissue visualisation and preserve facial nerve integrity. objectIves: To describe the functionality and feasibility of the use of methylene blue for parotidectomy in dogs. MaterIals and Methods: Retrospective study included seven client-owned dogs that underwent parotidectomy after injection of methylene blue from 2016 to 2019 in a referral centre. Cross-sectional imaging was used to confirm parotid gland surgical disease and for staging purposes. All dogs underwent parotid resection and removal of the parotid duct after injection of methylene blue. Methylene blue was either administered via cannulation of the parotid duct or directly injected into the abnormal gland. results: In all cases, the gland stained dark blue within seconds without any evident leakage. Complete parotid gland resection and removal of the parotid duct was achieved successfully in all dogs with a mean surgical time of 97 minutes. Subjectively, the staining was useful to identify innervation outside the coloured gland and facilitated dissection. No complications, including facial nerve injury, were recorded. clInIcal sIgnIfIcance: Methylene blue staining for complete parotidectomy was feasible, rapid and easy in these dogs. It can be used as an indirect facial nerve identification technique, and can therefore facilitate dissection and possibly reduce the incidence of post-operative facial nerve paralysis.

Outcomes and clinical features associated with surgically excised canine salivary gland carcinoma: A multi‐institutional, retrospective, Veterinary Society of Surgical Oncology study

“…13 Although only 7 dogs were included in that report, none of the dogs experienced facial nerve injury or other complications. 13 Furthermore, most cases of iatrogenic facial nerve injury have been reported to resolve within 3 months postoperatively. 14 Given the retrospective nature of the present study, a standardized follow-up time was not performed for the remaining 3 dogs in the long-term complication period, and their ultimate outcome remains unknown.…”

“…Facial nerve injury has been described as a complication of parotid sialoadenectomy for salivary mucocele in dogs, 12 as the facial nerve is intimately associated with the parotid salivary tissue. To minimize the risk of this complication, intraoperative visual contrast enhancement of the parotid salivary tissue (with or without a mass present) with methylene blue staining has been described with good success 13 . Although only 7 dogs were included in that report, none of the dogs experienced facial nerve injury or other complications 13 .…”

Computed tomographic findings in two dogs with chronic unilateral parotid duct ectasia

“…Diagnoses in these cases have been reached with a different combination of clinical examination, plain radiography, sialography, ultrasound and CT. CT has been used as part of the diagnostic investigation in only a few cases 6,23–25 …”

“…6,8,17,22,23 Diagnoses in these cases have been reached with a different combination of clinical examination, plain radiography, sialography, ultrasound and CT. CT has been used as part of the diagnostic investigation in only a few cases. 6,[23][24][25] Sialography is reported as diagnostic tool for salivary gland disorders, but it has also been used to establish the normal anatomy of salivary glands and their ducts in dogs and other species. 11,15 The use of sialography in combination with CT has been described in one ex vivo study in normal dogs, allowing good visualisation of the salivary glands and their ducts.…”

Intraoral approach for zygomatic sialoadenectomy in dogs: An anatomical study and three clinical cases

“…This was also the surgical resident's experience who was naïve to both techniques. Although injection of methylene blue has previously been used to describe parotid sialoadenectomy in cats and dogs, 19 the use of this technique as an objective measure of tissue visualization has not been validated to support its clinical value. However, it was the authors' opinion that it can be specifically useful in dogs with a neoplastic disease occurring for intraoperative visualization in comparison to a contrast sialography but not so useful in dogs with sialoceles due to the accumulation fluid and risk of leakage.…”