DISCUSSION
Sialendoscopy has enabled the assessment of ductal features and disease
status of diverse obstructive sialadenitis and changed the therapeutic
modality in salivary duct stenosis to gland-preserving minimally
invasive surgery.4,8 In a previous study, we evaluated
the prognostic factors related to sialendoscopy in 47 patients with
parotid duct stenosis who underwent sialendoscopic dilation as an
initial treatment.13 We found that sialendoscopy was
clinically satisfactory in relieving the symptoms of patients with
parotid duct stenosis. However, stenosis type and grade were
significantly associated with the success of the sialendoscopic
procedure. For instance, some patients with type 2 stenosis did not
respond to the sialendoscopic treatment and received revision surgery.
These results prompted us to investigate the therapeutic efficacy of
sialendoscopy combined with sialodochoplasty for treatment of type 2
stenoses and to clarify the indications for each surgery in type 2
stenosis.
In this study, we included type 2 stenosis cases that were
radiologically diagnosed, and all cases were confirmed as having type 2
stenosis based on sialendoscopic findings during operations. Parotid
duct stenoses encompass different types of stenosis in the duct, in
which type 2 stenosis features a focal web-like stricture and
accompanying megaduct.7 Whereas type 1 inflammatory
stenosis may be a precursor form of type 3 fibrotic stenosis, a focal
web-like stenosis accompanying megaduct appears to be a distinct type
with a different underlying pathogenesis that is not yet fully
understood.7 MR sialography is now being considered a
preferred technique for the detection of salivary duct stenosis, owing
to its non-invasive nature and non-exposure of
radiation.18 Sialendoscope-based visualization is also
needed because tissue characteristics of the residual duct are important
for defining different types of stenosis in addition to the feature of
stenotic portion. Furthermore, the radiologically diagnosed stenosis may
not always correspond with sialendoscope-based stenosis, as MR
sialography cannot exclude false-positive findings, such as physiologic
narrowing.
Different treatment strategies have been proposed for various types of
stenosis and sialendoscopic dilation has become the first-line treatment
for type 2 stenosis. In contrast, types 1 and 3 stenoses allow for
conservative care, including sialagogue, gland massage, intraductal
saline or steroid instillation, and botulinum toxin
injection.10 Salivary duct stenosis can be treated by
dilation using the sialendoscope itself by increasing the diameter of
the sialendoscope, and also by using various instruments, such as
dilators, balloons, and bougies.19 Focally-located,
low-grade strictures, and strictures in the distal duct may be the best
indications for sialendoscopic dilation. However, diffuse stenoses,
high-grade strictures, or inaccessible stenoses in the proximal to
mid-duct remain a sialendoscopic challenge.13 An
attempt can be made to create an opening using a micro drill with a
guide wire in high-grade stenoses in which endoscope fails to enter the
proximal lumen over the stricture. However, it often poses a high risk
of recurrence and sometimes complications, such as ductal perforation.
Transoral sialodochoplasty can be an additional treatment option if the
stricture is located in the distal duct based on preoperative radiologic
examinations and if sialendoscopic findings are suggestive of high-grade
strictures with a high risk of failure or
complication.16,19 In this study, excision of the
distal duct, including the stenotic portion, and the creation of a
neo-orifice allowed obstructive symptom improvement (complete resolution
in 46.2% and partial resolution in 53.8%) in patients, and no
recurrence was observed during follow-up. Moreover, widened neo-papilla
decreased in size over time and remained well-maintained during
follow-up without re-stricture (Fig. 2). We also compared pre- and
postoperative changes in the megaduct diameter and excretory salivary
flow. Intriguingly, postoperative MR sialography showed that the
diameter of megaducts significantly decreased after the transoral
sialodochoplasty, and some of the patients (71.4%) returned to almost
normal levels. MR sialography showed salivary gland ducts more clearly
after the operation, owing to the increases in saliva excretion after
stimulation with sialagogues. Although the distal duct beyond the
stenotic portion could be visualized after the transoral
sialodochoplasty, most patients still showed saliva stasis, probably as
the thin walls of the megaducts could not fully recover the naïve
contraction ability.
Sialendoscopic dilation is the only feasible technique when the stenotic
portion is proximally located and when the dilated duct cannot be pulled
to connect with the oral mucosa. Recently, an external combined approach
using excision with end-to-end anastomosis or excision with an
intervening vein graft has been introduced to treat cases of long
segments of type 3 stenosis or when sialendoscopic dilation
fails.20 Further studies are needed to investigate the
efficacy of combined techniques (transoral or transfacial
sialodochoplasty) for gland-preserving management of salivary duct
stenosis.21
This study had some limitations. First, due to its nonrandomized
retrospective design, the study could not prevent selection bias related
to the indications of the procedure. Second, the low number of patients
and short follow-up period of this study did not allow for a conclusive
analysis regarding the efficacy and recurrence of procedures, although,
to date, we have not found any recurrences in our sialodochoplasty
cohort. Nevertheless, we have demonstrated that transoral
sialodochoplasty is a useful procedure for improving salivary excretory
flow and repairing dilated duct, especially in type 2 parotid duct
stenosis with a megaduct.
In conclusion, we suggest that type 2 parotid duct stenosis can be
successfully treated with sialendoscopy combined with transoral
sialodochoplasty, which is recommended for patients with severe degrees
of distal stricture accompanying a large megaduct and consequently
decreased excretory salivary outflow. Further long-term, randomized
studies are required to compare the benefits and drawbacks of
sialendoscopy versus sialodochoplasty for the treatment of various types
of stenosis.