Parotid Salivary Duct Stenosis Following Caudal Maxillectomy Lisa A. Mestrinho, DVM, MS; Pedro B. Faísca, DVM, DEA, PhD; Maria MRE Niza, DVM, PhD Summary:
Parotid salivary duct dilation was diagnosed in a 9-year-old male dog. The dog had undergone caudal maxillectomy on the ipsilateral side 2-years prior to presentation. Treatment consisted of parotid salivary duct excision and superficial parotidectomy that lead to the resolution of clinical signs. Transient facial neuropraxia was observed immediately after surgery and resolved spontaneously after 2-weeks. Parotid salivary duct dilation should be considered as a chronic postoperative complication following caudal maxillectomy. J Vet Dent 31 (1); 40-43, 2014
Case Report
A 9-year-old, 35.0 kg male, mix-breed dog was referred for evaluation of progressive facial swelling of the right cheek (Fig.1). There were no other abnormalities on physical examination. The swelling palpated as a tubular lesion that was well demarcated, soft, and mobile extending from the right cheek to the parotid gland area. There was no erythema and the regional lymph nodes were not enlarged. The dog showed no clinical signs of pain while eating. The dog had received a caudal maxillectomy as surgical treatment for peripheral acanthomatous ameloblastoma 2-years before presentation. Caudal maxillectomy was performed in order to achieve 2-cm tumor-free margins. Surgical margins included bone and soft tissues of the right caudal maxilla and palatine bone to midline, and 1-cm dorsal to the tooth roots of the right maxillary fourth premolar, and first and second molar teeth. The parotid duct papilla and perioral duct segment were not identified prior to surgery and were presumed to have been included in the resected tissue. The owners reported a slow and progressive increase in the size of the swelling beginning 1-year prior to presentation, however the swelling had been relatively unchanged during the most recent 6-month period. Laboratory tests including a complete blood count (CBC) and biochemistry profiles were within normal range. Aspiration cytology revealed a thick, brown fluid with low degenerated cellular content and some evidence of chronic inflammation. The parotid duct papilla was not identified in the oral cavity nor were any abnormalities identified in the oral mucosa (Fig. 1). Computed tomography (CT) with contrast enhancement showed a well-defined, cystic, unilocular lesion within the subcutaneous soft tissues of the right cheek continuing along the mandibular and submandibular regions. The mass was closely associated with, and seemed to arise from the superficial lobe of the parotid salivary gland. There was a thick peripheral wall around the fluid-filled lesion. The margins of the lesion were smooth and well defined. There was no obvious communication with vascular structures and the parotid salivary gland appeared atrophied (Figs. 2 and 3). Parotid duct dilation was diagnosed based on physical examination and CT findings. The treatment 40
AAA379.indd 40
plan was to undertake a surgical approach to excise the parotid gland salivary duct and superficial parotidectomy. The dog was sedated with acepromazinea (0.05 mg/kg) and morphineb (1.0 mg/kg) IM. Anesthesia was induced with midazolamc (0.2 mg/kg) and propofold (1.0 mg/kg) IV. Anesthesia was maintained with isoflorane and oxygen. A warmed intravenous electrolyte solutione was administered (5.0 ml/kg/hr). The patient was placed on the operating table and covered with a blanket and warm rubber water bottles used to maintain body temperature. The animal was monitored using a multi-parameter anesthetic monitor with ECG, pulse oximetry, capnography, oscillometric arterial pressure, and temperature probe. Carprofenf (4.0 mg/kg) and morphine (0.5mg/kg) were administered every 4-hours for intra- and postoperative pain management. Antibiotic treatment consisted of amoxicillin potentiated with clavulanic acidg (15.0 mg/kg). A lateral approach to the cheek was performed and the parotid duct was dissected from the surrounding tissue (Fig. 4). The dissection was continued to the parotid salivary gland and a superficial parotidectomy was performed. Intraoperative assessment of the parotid salivary gland confirmed the CT
Figure 1 Photographs in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. Note the right facial swelling (A). The intraoral view shows the healed surgery site (B).
J VET DENT Vol. 31 No.1 Spring 2014
4/8/14 9:09 AM
Figure 2
Figure 3
Computed tomographic (CT) images in a 9-yearold mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. The non-enhanced (A) and enhanced (B) cross section views show the dilated parotid salivary gland duct (arrows) in the subcutaneous soft tissues of the right cheek. A different non-enhanced view (C) shows the atrophied ipsilateral parotid salivary gland (arrow).
Computed tomographic (CT) images in a 9-yearold mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. The non-enhanced (A) and enhanced (B) saggital views show the dilated parotid salivary gland duct (arrows) in the subcutanous soft tissues of the right cheek.
C
J VET DENT Vol. 31 No. 1 Spring 2014
AAA379.indd 41
41
4/3/14 7:49 AM
Figure 4
Figure 5
Photographs in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy showing the lateral approach (A) and excision (B) of the dilated parotid salivary gland duct.
Photomicrograph in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy showing pseudostratified parotid duct epithelium with tall principal cells, and smaller basal and goblet cells [H & E; original magnification = 400X].
findings of atrophy. The excised parotid salivary duct and gland were submitted for histopathological evaluation. Histopathology assessment documented a dilated, tubular structure with cuboidal to pseudostratified epithelium, with the presence of an inflammatory, granulomatous infiltrate of the duct wall. Lymphatic vessels were enlarged and some hemorrhagic areas were present (Fig. 5). Histopathology confirmed the clinical diagnosis of parotid duct dilation. The animal recovered from anesthesia without complication and was discharged 24-hours postoperatively. There were signs of postoperative facial neuropraxia with an absent lateral palpebral reflex. These signs resolved 2-weeks following surgery. There were no other complications noted following surgery. The 6-month postoperative evaluation indicated no signs of recurrence.
Discussion
The parotid duct results from a confluence of 2 to 3 parotid gland salivary duct branches.1 It curves rostrally over the masseter muscle, passes the buccinator muscle and ends on a prominent papilla at the level of the maxillary fourth premolar tooth.1 When performing a caudal maxillectomy, the parotid duct and papilla can easily be purposefully resected or inadvertently damaged due to its inclusion in the surgical field especially when a wide surgical margin is required. In humans, parotid duct ligation, injury, or excision may lead 42
AAA379.indd 42
to dilation in about 10 % of cases.2 In animals, parotid salivary gland duct dilation has been reported in the horse3, goat4, and dog5,6. Possible causes of parotid duct dilation described in the dog include traumatic injuries, sialolith, or inflammation.5,7 The prevalence of parotid duct dilation has not been determined in the dog, however experimental ligation of the mandibular salivary gland duct in dogs did not show mucocele, cyst, or sialolith formation.8 Prevalence of parotid duct dilation after caudal maxillectomy has not been assessed, probably because this complication is unusual. In the veterinary literature, parotid duct dilation after maxillectomy has only been reported in 1 dog.6 In this case, a caudal maxillectomy for a benign neoplasm had been performed 3-years before treatment for parotid salivary gland duct dilation. Similarly, in the case reported here, the complication of parotid salivary gland duct dilation was a chronic complication of caudal maxillectomy. Generally, healing following salivary duct transection results in duct stenosis and secondary atrophy of the parent salivary gland. We propose that in these 2 cases the gland may have initially undergone atrophy and then became productive with dilation secondary to ductal stenosis.9 Treatment options for parotid salivary duct injury include duct ligation, duct anastomosis, marsupialization, and resection of the parotid salivary gland.4,5,6,10 Treatment in this case included excision of the dilated duct segment and superficial parotidectomy in deference to duct marsupialization. Marsupialization to the mouth or skin was not considered based on the chronicity of the dilation, and the recent (6-months) static nature of the dilation that would most likely be related to gland atrophy and cessation of saliva production. Further, the dilated duct remnant was caudal to the oral cavity prohibiting formation of an oral stoma. Cutaneous marsupialization was not considered acceptable since the result would lead to permanent discharge of saliva to the lateral face. In humans, mucocele excision and superficial parotidectomy can be performed leading to the resolution of clinical signs even
J VET DENT Vol. 31 No.1 Spring 2014
4/3/14 7:49 AM
in cases of parotid salivary gland atrophy.11 However, parotid salivary gland resection is a difficult surgery with potential debilitating complications and should be avoided if possible.12 Parotid salivary gland resection significantly increased (32 % of cases) the risk of iatrogenic trauma and transient facial nerve paralysis due to the proximity of the facial nerve to the parotid salivary gland in humans.13,14 In this case report, transient facial neuropraxia was observed immediately after surgery, which persisted for 2-weeks. Clinical signs were limited to loss of palpebral reflex, which was treated by application of ophthalmic lubrication ointment QID. Parotid duct dilation should be considered a chronic postoperative complication of caudal maxillectomy. Parotid duct excision and partial parotidectomy may be considered for treatment of this complication. __________________________________________________ c d e f g a
b
Calmivet, Vetoquinol, Barcarena, Portugal Morfina 1% BBraun Medical, Barcarena, Portugal Midazolam 5mg/3ml, BBraun, Barcarena, Portugal Propofol limpuro 1% BBraun Medical, Barcarena, Portugal NaCl 0,9% BBraun Medical, Barcarena, Portugal Rimadyl, Pfizer Saúde Animal, Oeiras, Portugal Synulox Pfizer Saúde Animal, Oeiras, Portugal
Author Information
From the Interdisciplinary Centre of Research in Animal Health, Faculty of Veterinary Medicine, Technical University of Lisbon, Av. da Universidade Técnica – 1300-477 Lisbon, Portugal; and, the Centre of Research in Veterinary Sciences (Faisca), Faculty of Veterinary Medicine, Lusófona University, Av. Campo Grande, 376 – 1749-024 Lisboa, Portugal. Email: [email protected]
Acknowledgments
The authors thank Dr. Peter Haseler for language and editorial assistance.
References 1. Tadjalli M, Dehghani SN, Basiri M. Sialography in the dog: normal appearance. Vet Archiv 2004; 74: 225-233. 2. Shirley WP, Hill Js, Wooley AL, Wiatrak BJ. Success and complications of four duct dilation for siallorrhea. Int J Pediatr Otorhinolaryngol 2003; 67: 1-6. 3. Talley MR, Modransky PD, Welker FH, Smith MM, Dubbin ES. Congenital atresia of the parotid salivary duct in a 7-month-old quarter horse colt. J Am Vet Med Assoc 197; 1990:1633-1634. 4. Slocombe RF. Cystic Dilatation of the parotid gland of a goat. Can Vet J 1980; 21: 130-132. 5. Ladlow JF, Gregory SP. Parotid duct dilation in two dogs. J Small Anim Pract 2003; 44: 367-369. 6. Muir P, Rosin E. Parotid duct obstruction after caudal maxillectomy in a dog. Vet Rec 1995; 136: 46. 7. Jeffreys DA, Stasiw A, Dennis R. Parotid sialolithiasis in a dog. J Small Anim Pract 1996; 37: 296-297. 8. De Young DW, Kealy JK, Kluge JP. Attemps to produce salivar cysts in the dog. Am J Vet Res 1978; 39: 185-186. 9. Smith MM. Surgery of the canine salivary system. Comp of Contin Educ Pract Vet, 7; 1985:457-465. 10. Harvey CE. Parotid duct rupture and fistula in dog and cat. J Small Anim Pract 1977; 18: 163-168. 11. Ong CA, Loganathan A, Prepageran N, Rahmat O, Lingham OR. Parotid duct mucocele. Med J Malaysia 2005; 60: 644-646. 12. Smith MM, Waldron DR. Approach to the parotid salivary gland. Atlas of approaches for general surgery of the dog and cat. Philadelphia: WB Saunders, 1993; 88-91. 13. Koch M, Zenk J, Iro H. Long term results of morbility after parotid gland surgery in benign disease. Laryngoscope 2010; 120: 724-730. 14. Nouraei SA, Ismail Y, McLean NR, Thomson PJ, Milner RH, Welch AR. Surgical treatment of chronic parotid sialadenitis. J Laryngol Otol 2007; 121: 880-884.
J VET DENT Vol. 31 No. 1 Spring 2014
AAA379.indd 43
43
4/3/14 7:49 AM
Parotid salivary duct dilation was diagnosed in a 9-year-old male dog. The dog had undergone caudal maxillectomy on the ipsilateral side 2-years prior to presentation. Treatment consisted of parotid salivary duct excision and superficial parotidectomy that lead to the resolution of clinical signs. Transient facial neuropraxia was observed immediately after surgery and resolved spontaneously after 2-weeks. Parotid salivary duct dilation should be considered as a chronic postoperative complication following caudal maxillectomy. J Vet Dent 31 (1); 40-43, 2014
Case Report
A 9-year-old, 35.0 kg male, mix-breed dog was referred for evaluation of progressive facial swelling of the right cheek (Fig.1). There were no other abnormalities on physical examination. The swelling palpated as a tubular lesion that was well demarcated, soft, and mobile extending from the right cheek to the parotid gland area. There was no erythema and the regional lymph nodes were not enlarged. The dog showed no clinical signs of pain while eating. The dog had received a caudal maxillectomy as surgical treatment for peripheral acanthomatous ameloblastoma 2-years before presentation. Caudal maxillectomy was performed in order to achieve 2-cm tumor-free margins. Surgical margins included bone and soft tissues of the right caudal maxilla and palatine bone to midline, and 1-cm dorsal to the tooth roots of the right maxillary fourth premolar, and first and second molar teeth. The parotid duct papilla and perioral duct segment were not identified prior to surgery and were presumed to have been included in the resected tissue. The owners reported a slow and progressive increase in the size of the swelling beginning 1-year prior to presentation, however the swelling had been relatively unchanged during the most recent 6-month period. Laboratory tests including a complete blood count (CBC) and biochemistry profiles were within normal range. Aspiration cytology revealed a thick, brown fluid with low degenerated cellular content and some evidence of chronic inflammation. The parotid duct papilla was not identified in the oral cavity nor were any abnormalities identified in the oral mucosa (Fig. 1). Computed tomography (CT) with contrast enhancement showed a well-defined, cystic, unilocular lesion within the subcutaneous soft tissues of the right cheek continuing along the mandibular and submandibular regions. The mass was closely associated with, and seemed to arise from the superficial lobe of the parotid salivary gland. There was a thick peripheral wall around the fluid-filled lesion. The margins of the lesion were smooth and well defined. There was no obvious communication with vascular structures and the parotid salivary gland appeared atrophied (Figs. 2 and 3). Parotid duct dilation was diagnosed based on physical examination and CT findings. The treatment 40
AAA379.indd 40
plan was to undertake a surgical approach to excise the parotid gland salivary duct and superficial parotidectomy. The dog was sedated with acepromazinea (0.05 mg/kg) and morphineb (1.0 mg/kg) IM. Anesthesia was induced with midazolamc (0.2 mg/kg) and propofold (1.0 mg/kg) IV. Anesthesia was maintained with isoflorane and oxygen. A warmed intravenous electrolyte solutione was administered (5.0 ml/kg/hr). The patient was placed on the operating table and covered with a blanket and warm rubber water bottles used to maintain body temperature. The animal was monitored using a multi-parameter anesthetic monitor with ECG, pulse oximetry, capnography, oscillometric arterial pressure, and temperature probe. Carprofenf (4.0 mg/kg) and morphine (0.5mg/kg) were administered every 4-hours for intra- and postoperative pain management. Antibiotic treatment consisted of amoxicillin potentiated with clavulanic acidg (15.0 mg/kg). A lateral approach to the cheek was performed and the parotid duct was dissected from the surrounding tissue (Fig. 4). The dissection was continued to the parotid salivary gland and a superficial parotidectomy was performed. Intraoperative assessment of the parotid salivary gland confirmed the CT
Figure 1 Photographs in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. Note the right facial swelling (A). The intraoral view shows the healed surgery site (B).
J VET DENT Vol. 31 No.1 Spring 2014
4/8/14 9:09 AM
Figure 2
Figure 3
Computed tomographic (CT) images in a 9-yearold mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. The non-enhanced (A) and enhanced (B) cross section views show the dilated parotid salivary gland duct (arrows) in the subcutaneous soft tissues of the right cheek. A different non-enhanced view (C) shows the atrophied ipsilateral parotid salivary gland (arrow).
Computed tomographic (CT) images in a 9-yearold mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy. The non-enhanced (A) and enhanced (B) saggital views show the dilated parotid salivary gland duct (arrows) in the subcutanous soft tissues of the right cheek.
C
J VET DENT Vol. 31 No. 1 Spring 2014
AAA379.indd 41
41
4/3/14 7:49 AM
Figure 4
Figure 5
Photographs in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy showing the lateral approach (A) and excision (B) of the dilated parotid salivary gland duct.
Photomicrograph in a 9-year-old mix-breed dog with parotid salivary gland duct dilation secondary to complications from caudal maxillectomy showing pseudostratified parotid duct epithelium with tall principal cells, and smaller basal and goblet cells [H & E; original magnification = 400X].
findings of atrophy. The excised parotid salivary duct and gland were submitted for histopathological evaluation. Histopathology assessment documented a dilated, tubular structure with cuboidal to pseudostratified epithelium, with the presence of an inflammatory, granulomatous infiltrate of the duct wall. Lymphatic vessels were enlarged and some hemorrhagic areas were present (Fig. 5). Histopathology confirmed the clinical diagnosis of parotid duct dilation. The animal recovered from anesthesia without complication and was discharged 24-hours postoperatively. There were signs of postoperative facial neuropraxia with an absent lateral palpebral reflex. These signs resolved 2-weeks following surgery. There were no other complications noted following surgery. The 6-month postoperative evaluation indicated no signs of recurrence.
Discussion
The parotid duct results from a confluence of 2 to 3 parotid gland salivary duct branches.1 It curves rostrally over the masseter muscle, passes the buccinator muscle and ends on a prominent papilla at the level of the maxillary fourth premolar tooth.1 When performing a caudal maxillectomy, the parotid duct and papilla can easily be purposefully resected or inadvertently damaged due to its inclusion in the surgical field especially when a wide surgical margin is required. In humans, parotid duct ligation, injury, or excision may lead 42
AAA379.indd 42
to dilation in about 10 % of cases.2 In animals, parotid salivary gland duct dilation has been reported in the horse3, goat4, and dog5,6. Possible causes of parotid duct dilation described in the dog include traumatic injuries, sialolith, or inflammation.5,7 The prevalence of parotid duct dilation has not been determined in the dog, however experimental ligation of the mandibular salivary gland duct in dogs did not show mucocele, cyst, or sialolith formation.8 Prevalence of parotid duct dilation after caudal maxillectomy has not been assessed, probably because this complication is unusual. In the veterinary literature, parotid duct dilation after maxillectomy has only been reported in 1 dog.6 In this case, a caudal maxillectomy for a benign neoplasm had been performed 3-years before treatment for parotid salivary gland duct dilation. Similarly, in the case reported here, the complication of parotid salivary gland duct dilation was a chronic complication of caudal maxillectomy. Generally, healing following salivary duct transection results in duct stenosis and secondary atrophy of the parent salivary gland. We propose that in these 2 cases the gland may have initially undergone atrophy and then became productive with dilation secondary to ductal stenosis.9 Treatment options for parotid salivary duct injury include duct ligation, duct anastomosis, marsupialization, and resection of the parotid salivary gland.4,5,6,10 Treatment in this case included excision of the dilated duct segment and superficial parotidectomy in deference to duct marsupialization. Marsupialization to the mouth or skin was not considered based on the chronicity of the dilation, and the recent (6-months) static nature of the dilation that would most likely be related to gland atrophy and cessation of saliva production. Further, the dilated duct remnant was caudal to the oral cavity prohibiting formation of an oral stoma. Cutaneous marsupialization was not considered acceptable since the result would lead to permanent discharge of saliva to the lateral face. In humans, mucocele excision and superficial parotidectomy can be performed leading to the resolution of clinical signs even
J VET DENT Vol. 31 No.1 Spring 2014
4/3/14 7:49 AM
in cases of parotid salivary gland atrophy.11 However, parotid salivary gland resection is a difficult surgery with potential debilitating complications and should be avoided if possible.12 Parotid salivary gland resection significantly increased (32 % of cases) the risk of iatrogenic trauma and transient facial nerve paralysis due to the proximity of the facial nerve to the parotid salivary gland in humans.13,14 In this case report, transient facial neuropraxia was observed immediately after surgery, which persisted for 2-weeks. Clinical signs were limited to loss of palpebral reflex, which was treated by application of ophthalmic lubrication ointment QID. Parotid duct dilation should be considered a chronic postoperative complication of caudal maxillectomy. Parotid duct excision and partial parotidectomy may be considered for treatment of this complication. __________________________________________________ c d e f g a
b
Calmivet, Vetoquinol, Barcarena, Portugal Morfina 1% BBraun Medical, Barcarena, Portugal Midazolam 5mg/3ml, BBraun, Barcarena, Portugal Propofol limpuro 1% BBraun Medical, Barcarena, Portugal NaCl 0,9% BBraun Medical, Barcarena, Portugal Rimadyl, Pfizer Saúde Animal, Oeiras, Portugal Synulox Pfizer Saúde Animal, Oeiras, Portugal
Author Information
From the Interdisciplinary Centre of Research in Animal Health, Faculty of Veterinary Medicine, Technical University of Lisbon, Av. da Universidade Técnica – 1300-477 Lisbon, Portugal; and, the Centre of Research in Veterinary Sciences (Faisca), Faculty of Veterinary Medicine, Lusófona University, Av. Campo Grande, 376 – 1749-024 Lisboa, Portugal. Email: [email protected]
Acknowledgments
The authors thank Dr. Peter Haseler for language and editorial assistance.
References 1. Tadjalli M, Dehghani SN, Basiri M. Sialography in the dog: normal appearance. Vet Archiv 2004; 74: 225-233. 2. Shirley WP, Hill Js, Wooley AL, Wiatrak BJ. Success and complications of four duct dilation for siallorrhea. Int J Pediatr Otorhinolaryngol 2003; 67: 1-6. 3. Talley MR, Modransky PD, Welker FH, Smith MM, Dubbin ES. Congenital atresia of the parotid salivary duct in a 7-month-old quarter horse colt. J Am Vet Med Assoc 197; 1990:1633-1634. 4. Slocombe RF. Cystic Dilatation of the parotid gland of a goat. Can Vet J 1980; 21: 130-132. 5. Ladlow JF, Gregory SP. Parotid duct dilation in two dogs. J Small Anim Pract 2003; 44: 367-369. 6. Muir P, Rosin E. Parotid duct obstruction after caudal maxillectomy in a dog. Vet Rec 1995; 136: 46. 7. Jeffreys DA, Stasiw A, Dennis R. Parotid sialolithiasis in a dog. J Small Anim Pract 1996; 37: 296-297. 8. De Young DW, Kealy JK, Kluge JP. Attemps to produce salivar cysts in the dog. Am J Vet Res 1978; 39: 185-186. 9. Smith MM. Surgery of the canine salivary system. Comp of Contin Educ Pract Vet, 7; 1985:457-465. 10. Harvey CE. Parotid duct rupture and fistula in dog and cat. J Small Anim Pract 1977; 18: 163-168. 11. Ong CA, Loganathan A, Prepageran N, Rahmat O, Lingham OR. Parotid duct mucocele. Med J Malaysia 2005; 60: 644-646. 12. Smith MM, Waldron DR. Approach to the parotid salivary gland. Atlas of approaches for general surgery of the dog and cat. Philadelphia: WB Saunders, 1993; 88-91. 13. Koch M, Zenk J, Iro H. Long term results of morbility after parotid gland surgery in benign disease. Laryngoscope 2010; 120: 724-730. 14. Nouraei SA, Ismail Y, McLean NR, Thomson PJ, Milner RH, Welch AR. Surgical treatment of chronic parotid sialadenitis. J Laryngol Otol 2007; 121: 880-884.
J VET DENT Vol. 31 No. 1 Spring 2014
AAA379.indd 43
43
4/3/14 7:49 AM
