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(Radiology. 2000;214:139-142.)
© RSNA, 2000

Vascular and Interventional Radiology

Interventional Radiology in the Removal of Salivary Calculi1

Nicholas A. Drage, FDS RCS, DDR RCR, Jackie E. Brown, MSc, FDS RCPS(Glasg), DDR RCR, Michael P. Escudier, MBBS, FDS RCS and Mark McGurk, MD, FRCS, DLO, FDS RCS

1 From the Departments of Dental Radiology (N.A.D., J.E.B.) and Oral and Maxillofacial Surgery (M.P.E., M.M.), U.M.D.S., Guy's Dental Hospital, Floor 23, Guy's Tower, London SE1 9RT, United Kingdom. Received September 28, 1998; revision requested, December 17; revision received, April 1, 1999; accepted April 22. Address reprint requests to M.M. (e-mail: mark.mcgurk@kcl.ac.uk).


   Abstract
TOP
 Abstract
Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To prospectively investigate the efficacy of a wire basket extractor in the retrieval of salivary calculi and establish selection criteria for suitable cases.

MATERIALS AND METHODS: Twenty-five consecutive patients (14 male, 11 female; age range, 13–69 years) with salivary calculi (20 submandibular, five parotid) were treated by using a commercially available wire basket extractor with intermittent fluoroscopic guidance.

RESULTS: Elimination of calculi was accomplished in 10 (40%) cases. In an additional seven (28%) cases, either part of the calculus was removed or whole calculi were removed with others remaining. Failure to retrieve any stone occurred in eight (32%) cases. The most common cause of failure was attachment of the calculus to the duct wall.

CONCLUSION: Interventional radiology provides a useful adjuvant method of calculus removal and complements extracorporeal lithotripsy. Basket retrieval of calculi has low morbidity and is rapid and less invasive than traditional surgery. It is most effective in retrieving mobile stones in the extraglandular parotid and submandibular ducts.

Index terms: Salivary glands, diseases, 264.818 • Salivary glands, interventional procedures, 264.1267 • Salivary glands, US, 264.1298


   Introduction
TOP
 Abstract
 Introduction
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
There is a general desire to move away from invasive surgery and toward minimally invasive procedures. In addition to reduced morbidity, these techniques usually have the added advantage of eliminating or reducing the demand on inpatient facilities. Minimally invasive methods are now the treatment of choice for urolithiasis; surgical salvage is restricted to less than 5% of patients (1). The techniques and equipment used in urolithiasis can be adapted for use in the salivary system, and initial experiences with extracorporeal salivary lithotripsy are promising (2).

The results of fluoroscopically guided basket retrieval of salivary calculi in a series of 25 consecutive patients is presented. The method can be used either to complement extracorporeal lithotripsy or, in selected cases, directly as an alternative to surgery. Minimally invasive procedures eliminate the risks related to general anesthesia and the morbidity associated with surgical removal of salivary glands, which includes neurologic damage (3,4), hemorrhage, scarring and cosmetic defects, and Frey syndrome (gustatory sweating) (5). We performed a prospective study to determine the usefulness of a wire basket extractor in the removal of salivary calculi and the criteria for the selection of suitable cases. The technique and criteria proposed to guide case selection are described.


   MATERIALS AND METHODS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Between October 1995 and April 1998, 336 patients with salivary gland disease were seen in the salivary gland clinic at Guy's Dental Hospital. One hundred seventy-two of these patients had a diagnosis of salivary calculi and were entered into a minimally invasive treatment protocol. From this group, 25 consecutive patients (14 male patients aged 13–61 years and 11 women aged 21–69 years) with calculi were entered into the study. The ethics committee at Guy's Hospital approved the study, and all the patients gave informed consent to undergo the treatment. The main presenting complaint, which 22 patients had, was gustatory pain and swelling. Other symptoms included infection associated with painful swelling in the floor of mouth. Symptoms ranged in duration from 3 months to 20 years and varied in frequency.

Fourteen patients had undergone salivary lithotripsy (Minilith; Stortz Medical, Kreuzlingen, Switzerland) previously and had residual stone fragments in the ductal system. In one case, targeting of a mobile calculus was difficult and in another, the patient was unable to tolerate lithotripsy.

The number and position of the stones were established by using sialography with a nonionic contrast medium (sodium and meglumine diatrizoate [Urografin]; Schering, Berlin, Germany). An ultrasonographic (US) examination also was performed in most of the patients to confirm the diagnosis and exclude any other disease. No patients underwent additional imaging in this study.

In one patient, the stone was in the distal portion of the submandibular duct. Nine patients had stones in the middle portion of the duct (parotid in one patient, submandibular in eight patients). Seven patients had stones in the proximal third of the main duct (parotid in two patients, submandibular in five patients). Four patients had calculi at the hilum or within the intraglandular ductal system (parotid in one patient, submandibular in three patients). The remaining four patients had calculi at more than one location (parotid in one patient, submandibular in three patients). Excluding the patient with 42 fragments, the average stone size was 3.4 mm (range, 1.5–9.0 mm), and the mean number of stones per patient was 1.67 (range, 1.0–5.0). Sixteen patients had a single calculus.

All procedures were performed on an outpatient basis with local anesthesia. Anesthesia in the submandibular region was induced by using an inferior dental nerve block of 2% lignocaine hydrochloride with 1:80,000 adrenaline. For parotid stones, the local anesthetic solution was infiltrated around the parotid papilla. In both procedures, anesthesia was assisted by mixing the local anesthetic solution with the contrast medium (iopromide [Ultravist 300]; Schering) used for sialography.

The ductal orifice was dilated by using a lacrimal duct dilator. A 0.018-inch straight guide wire with a 3-cm flexible tip was introduced into the duct, over which a tapered introducer was passed, followed by a 3.5-F outer sheath (modified Check-Flo II introducer; Cook, Bjaeverskov, Denmark). The guide wire and introducer were then removed, leaving the outer sheath in situ. The position of the stone (or stones) was then assessed by using fluoroscopic sialography (Multidiagnost 3; Philips Medical Systems, Best, the Netherlands). With intermittent fluoroscopic guidance, the wire basket (Captura Helical Stone Extractor with 3-F gauge; Cook Urological, Spencer, Ind) was passed down the duct to a point beyond the stone (Fig 1). Once positioned, the basket was opened and withdrawn slowly in a rotating action to engage the calculus. The basket was then closed and withdrawn, together with the sheath, until the stone was at the ostium (Fig 2). In 14 patients, who had larger stones, delivery of the basket and stone necessitated a small ostial incision.



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  		Figure 1. Lateral fluoroscopic image after introduction of contrast media into the right submandibular gland shows the tip of the basket (short arrow, 1) beyond the calculus (long arrows, 2).

 


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  		Figure 2. Lateral fluoroscopic image shows the calculus (arrows) in the basket, which has been withdrawn to the ostium.

 
Patients were examined, when possible, at the salivary gland clinic at 6 weeks and at 6 months postoperatively. They were questioned as to whether they had residual obstructive or infective symptoms. Those who were symptom free were not followed up further, whereas those who had persistent obstruction underwent further imaging and were subsequently offered an alternative treatment.


   RESULTS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Elimination of all stones from the duct was achieved in 10 (40%) patients, one of whom required two attempts. In nine patients, a single stone was present, whereas the remaining patient had multiple fragments (Table 1). Seven stones were mobile preoperatively, as judged by a change in position during the filling and emptying phases of sialography. Two stones, including one in the case with multiple fragments, were fully outlined by contrast media at sialography and were therefore considered to be mobile. The other stone was believed to be fixed to the duct wall at sialography.


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  		TABLE 1. Number, Site, Size, and Position of Salivary Gland Calculi in the Group in Which Complete Removal of Calculi Was Achieved
 
Incomplete removal of stone fragments due to multiple calculi or partial removal of a single stone was achieved in seven (28%) patients, one of whom underwent the procedure on two separate occasions. In these patients, a total of 20 calculi were present, 11 (55%) of which were completely retrieved and two (10%) of which were partially retrieved (Table 2). Of the stones removed completely, five were known to be mobile before the procedure and six were thought to be mobile on the basis of the sialographic findings.


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  		TABLE 2. Number, Site, Size, and Position of Salivary Gland Calculi in the Group in Which Partial Success in Calculi Removal Was Achieved
 
In eight (32%) patients, one of whom required two attempts, no stone was retrieved (Table 3). The probable causes of failure are listed in Table 4.


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  		TABLE 3. Number, Site, Size, and Position of Salivary Gland Calculi in the Group in Which Calculi Removal Was Unsuccessful
 

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  		TABLE 4. Likely Reasons for Failure to Remove the Calculi
 
Of the 10 patients successfully treated, eight (80%) were symptom free at follow-up (mean follow-up period, 8.65 months; range, 1.5–17.0 months). In comparison, none of the patients in whom partial success was achieved was asymptomatic at follow-up (mean follow-up period, 8.9 months; range, 1.5–15.0 months).

All patients had some tenderness and swelling of the gland postoperatively. This varied in duration from 1 to 7 days. Two (8%) patients developed a low-grade postoperative infection, which required antibiotic therapy. In one case, the calculus and basket became impacted in the gland and could not be withdrawn. Surgical intervention was required to free the device and retrieve the stone.


   DISCUSSION
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Salivary calculi account for more than 50% of cases of major salivary gland disease and are therefore the most common cause of acute and chronic salivary gland infections (6). The results of postmortem studies (7) indicate that calculi are present in 1.2% of the population, whereas analysis of hospital admission data indicates an incidence of 31–58 cases per million people annually (8). The peak incidence occurs between the ages of 30 and 60 years (9). The calculi grow by deposition and range in size from 0.1 to 30.0 mm (10). The majority (80%–90%) of calculi are found in the submandibular ductal system, whereas 5%–10% occur in the parotid ductal system and approximately 5% manifest in the sublingual and other minor salivary glands (10,11). Patients typically present with so called "meal-time syndrome," which is gustatory swelling of the gland (2).

The diagnosis of salivary calculi is based on the patient's history and clinical examination, which are supplemented by radiologic findings. The radiologic methods include conventional radiography, sialography, computed tomography (CT), magnetic resonance imaging, and US. CT is widely used and has the advantage of being very sensitive in the detection of calcifications (12); however, its disadvantages include poor demonstration of ductal changes (13), requirement of a relatively high radiation dose, and high cost. It has been our experience that CT does not add substantial new information to warrant its use.

We agree with the findings of van den Akker (14) that sialography remains the method of choice for investigation of obstructive disease. Sialography supplemented with US was used in this study because both methods have been shown to be accurate for the diagnosis of salivary calculi (14–16). Together, they demonstrate the morphologic features of the ducts proximal and distal to the obstruction and provide information on aspects of obstructive salivary gland disease that affect outcome—that is, the location and probable mobility of the stones. These details were points of consideration in our plans to use interventional basket retrieval.

The treatment options for salivary calculi are generally dictated by the position of the stone (2). Stones in the distal third of the Wharton duct and at the papilla of the Stenson duct are suitable for simple transoral surgical removal under local anesthesia. Those in the proximal part of the submandibular duct, at the hilum, or in the intraglandular ducts typically necessitate gland removal. Similarly, stones in the parotid intraglandular ducts necessitate superficial parotidectomy. With these surgical procedures, there is a risk (11%–36%) of neurologic damage to the facial nerve (3,4) and the lingual and hypoglossal nerves. Scarring at the incision site and Frey syndrome (5) are associated with additional morbidity.

New treatment modalities, such as extracorporeal and, more recently, intracorporeal salivary gland lithotripsy, offer alternative methods of managing salivary stones (2). In both techniques, the calculus is broken, and the fragments are subsequently washed down the duct. These methods are advantageous because the salivary glands have the ability to regain function following the removal of an obstruction (17,18). Extracorporeal lithotripsy has limitations: Stones in the middle third of the submandibular duct are closely related to the mandible and thus cannot be targeted. Similarly, the instrumentation required for intracorporeal lithotripsy, an endoscope and lithotriptor, is still in development and not very effective at present. In addition, some of the intracorporeal techniques are associated with ductal perforation (2).

Fluoroscopically guided basket stone retrieval does not have the above disadvantages and is a simple adjuvant method of retrieving persistent stone fragments after lithotripsy. This technique was reported in 1990 (19) and is still being refined. The success rates in three published studies (20–22) vary between 40% and 78%, with success defined as being stone free and asymptomatic. In the present series of 25 patients, some of the calculus was retrieved in 68% of patients, but complete elimination of the stone from the ductal system was achieved in only 40%.

Stones that are not completely outlined by contrast media on sialograms have a higher removal failure rate (22) because they are thought to be tethered to the duct wall and hence difficult to ensnare. The results reported herein support this finding. In addition, calculi in the intraglandular ducts are difficult to remove (20) because they are more inaccessible to the basket. In our study, it was not possible to capture calculi in the diverticula off the ductal system for the same reason.

The selection criteria that provide optimal stone removal are a mobile stone, or fragment, in the extraglandular part of the parotid or submandibular duct. Mobility is judged clinically on the basis of a history of intermittent mealtime syndrome or the ability of the patient to relieve obstruction by manipulating the calculus. The clinician also may be able to move the stone. If we had attempted the described basket removal procedure in only those patients who fulfilled these criteria (10 patients), then we would have eliminated all the stones in eight (80%) patients and failed to retrieve any stones in two (20%).

Movement of the calculus during sialography provides radiologic evidence of mobility. Complete outlining of the calculus with contrast media and dilatation of the duct proximal to the calculus are suggestive of a freely mobile calculus.

Parotid ductal calculi are difficult to assess clinically owing to the thickness of the overlying soft tissues. In addition, the parotid duct is narrower, more tortuous, and more difficult to negotiate than the submandibular duct. However, the rate of successful stone clearance in both glands was the same (40%). Large calculi, which, by definition, are those that have been in the gland for a considerable period, can cause a fibrous reaction, which forms an inelastic ductal cavity from which the stone cannot be retrieved.

In conclusion, the management of salivary calculi by using minimally invasive techniques is becoming a more realistic approach. Basket retrieval may be used for mobile calculi or fragments in the middle and proximal thirds of the submandibular duct or for those in any region of the parotid duct. It is a simple, inexpensive, low-morbidity outpatient procedure that, according to our study results, has a success rate of 40%. This rate can be substantially improved with appropriate case selection, the criteria for which we have reported.


   Footnotes
 
Author contributions: Guarantors of integrity of entire study, all authors; study concepts and design, all authors; definition of intellectual content, all authors; literature research, N.A.D., J.E.B., M.P.E.; clinical studies, N.A.D., J.E.B., M.P.E.; data acquisition and analysis, N.A.D., J.E.B., M.P.E.; manuscript preparation, N.A.D., J.E.B., M.P.E.; manuscript editing and review, all authors.


   References
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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