Abstract
In the head and neck area, a large proportion of clinically relevant fistulas occur in childhood. The present case describes the use of contrast enhanced ultrasound with intraductal administration of the contrast medium for preoperative visualization of the fistula duct in the case of a second brachial cleft fistula. This provided the surgeon with important additional information, such as the detailed course of the fistula and its relation to the large vessels of the neck. The method can help to improve surgical planning, reduce radiation exposure and to avoid imaging under general anesthesia, especially in children.
Background
Second branchial cleft fistulas are caused by incomplete regression of the second branchial cleft. Due to the risk of recurrent inflammation and associated complications (e.g. abscess), the fistula should be surgically removed. Complete fistula excision is crucial to prevent recurrence. This may require the performance of a tonsillectomy in some cases [1].
The diagnosis is usually made in childhood based on history and clinical findings. Supplementary imaging is not always mandatory, but can supply the surgeon with additional information, in particular the relationship of the fistula duct to the extracranial cerebral vessels as well as the length of the duct structure. In principle, computer tomography (CT) and magnetic resonance imaging (MRI), as well as B-scan ultrasonography (US), are suitable for this purpose. In general CT is easily available in comparison, but radiation exposure is unfavorable particularly in children. MRI is useful for assessing the positional relationship between pathology and other soft tissue structures of the neck and CT-fistulography is useful for detailed visualization of the course of the duct but leeds to radiation exposure. High resolution B-scan US could provide vizualization of soft tissue structures of the neck, is easily available, cost effective and without radiation [2–5].
However, all of the above procedures have additional specific limitations. CT diagnosis can be limited by artifacts of the jaw. A spiral CT of the neck with contrast medium or a CT-fistulography, in which the contrast medium is applied directly into the fistula duct, are usually used. This requires a serial CT. For MRI children mostly need sedation or short anesthesia. In B-scan US the fistula tract cannot always be depicted reliably even with high-resolution transducers up to 20 MHz. Currently, there is no general agreement on the best imaging method [2, 5]. Intraoperative endoscopic visualization of the fistula tract has also been described as an alternative technique [6].
Contrast-enhanced ultrasound (CEUS) is increasingly used in clinical practice of various specialties. Generally, an intravenous administration of the contrast agent is used to precisely visualize the perfusion. However, other forms of application have also been described [7]. The side effects of ultrasound contrast media are minimal compared to those of an CT- contrast medium.
The present case is about the excision of a second branchial cleft fistula with an intraoperative visualization of the fistula duct using CEUS. The contrast medium was injected directly into the fistula duct. The method was only described in a conference paper in 2012 [8].
Case
The six year old patient was first seen in our department because of a persistent foreign body sensation in the mouth. Since birth, there was a known fistula on the right side of the neck with occasional secretion of fluid. There were no other preexisting diseases. A cystic mass was found at the upper pole of the right tonsil. In addition, the right anterior border of the sternocleidomastoid muscle showed a fistula mouth without irritation. B-scan US revealed an echo-deficient mass dorsal to the tonsil, which confirmed the suspicion of a cyst. The fistula duct could not be reliably visualized in B-scan US with an 18Mhz linear transducer. Due to the recurrent secretions and the feeling of a foreign body enoral, there was an indication for fistula resection including tonsillectomy. The informed consent included the option for multiple small horizontal incisions (see Fig. 1c). In addition the “off-label” use of the intraductal application of the ultrasound contrast agent Sonovue (Bracco, Milan, Italy) was explored. The value of CEUS for the detection of fistulas in other areas has already been demonstrated [7]. Corresponding applications can be found in current recommendations of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) [9].
Presentation of the intraoperative situation. A shows the intraoperative use of the sonography, B the cannula inserted into the fistula mouth. C Marked planned incisions. The yellow arrow points to the fistula mouth, which has been cut around in an elliptical shape. The blue arrow points to the optional auxiliary incision, the star highlights the marked jaw angle. D in toto resected specimen.
CEUS of the fistula duct with 1 ml of Sonovue (see Fig. 1a) was performed in the operating theatre on an already narcotized patient. The course of the duct up to the cyst inside the right tonsillar lodge could be completely visualized (see Fig. 2). Afterwards, the fistula and cyst were routinely colored with methylene blue to improve the intraoperative identification of the delicate fistula tract (see Fig. 3a).
Examples of contrast enhanced ultrasound of the fistula duct. A and B show the fistula duct (yellow arrow), which can be traced through the contrast medium to its confluence with the cyst inside the tonsillar fossa (red arrow in C and D). TO: right tonsil, TB: tongue base, GSM: submandibular gland.
Images of the oral intraoperative setting. A: Initial situation before beginning the oral preparation. The uptake of methylene blue through the cyst * can be seen clearly. B: The enoral part of the fistula duct is completely shown. Leaked dye disturbs the surgical view. C: Enoral view of the complete fistula tract. The former fistula mouth can be seen centrally.
The fistula mouth was incised in an elliptical shape and visualization of the fistula duct was started at the anterior border of the sternocleidomastoid muscle. From here, the duct was followed to the tonsillar fossa. This was combined with enoral careful dissection of the cyst, visualization of the fistula tract (see Fig. 3b) and right-sided tonsillectomy. Finally, the fistula duct could be completely pulled towards enoral (see Fig. 3c). Pharyngeal defect was closed with absorbable sutures and covered with Tachosil (Corza Medical, Westwood, USA). Thanks to the optimal visualization of the fistula duct by CEUS, there was no doubt of a connection between the fistula duct and the tonsillar fossa and the whole route of the fistula duct was known. The transoral operation was started immediately after the fistula duct was safely visualized up to the pharyngeal wall. Since the dissection of the fistula duct up to the pharyngeal wall could be performed bluntly via the single neck incision and a transcervical detachment was not primarily required, there was no need for additional incisions. The operation could thus be performed with maximum gentleness for our young patient. Methylene blue coloring was able to show the complete course of the fistula indirectly by coloring the cyst, however, in some cases it is known to be rather disabling for microsurgical dissection when the dye leaks out. In the present case, the in toto excision was successful (see Fig. 1d).
Postoperative recovery was without complications and the patient could be discharged on the 5th postoperative day. Histology confirmed a lateral neck fistula.
By using CEUS with intraductal administration, the course of the fistula duct could be precisely visualized. This provided the surgeon with important additional information compared to pure B-scan sonography alone. CT and MRI were not necessary in this case. CEUS can be an informative preoperative diagnostic method in similar cases and could be an additional tool to allow a safe and minimally invasive procedure for the patients.
Declarations of interest
Julian Künzel received fees for lectures from GE Healthcare (Chicago, Illinois, USA).