TWENTY-SIX: Ultrasonography of the Soft Tissue Structures of the Neck

Ultrasonography of the Soft Tissue Structures of the Neck


Massimo Magri


Clinica Veterinaria Spirano, Spirano (BG), Italy


Preparation and Scanning Technique


Optimal equipment for ultrasonography of structures of the neck should include a high frequency, 10–12 MHz linear probe and a 6.6 MHz micro-convex probe. These two probes allow visualization with maximal definition of both superficial and deep structures. However, many structures of the neck can be visualized using only a 5–7.5 MHz linear probe typically used for equine obstetrics. Best images are obtained by clipping the hair with a surgical clipper blade and applying coupling gel; however, alcohol will also serve as an adequate contact medium. Ideally, place an examination glove or similar over the probe because continued exposure to coupling gel, particularly alcohol, can cause degradation of the probe and potentially affect image quality and life span of the probe (Figure 26.1).

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Figure 26.1    Probe protection. Protect the probe from coupling gel or alcohol with an examination glove or similar covering.

Orientation of the probe must be kept constant over time to obtain comparable images. When scanning in the longitudinal axis (Figure 26.2A), orientate the probe so that distal structures are on the left side of the screen and proximal structures are on the right (Figure 26.2B). When scanning in the cross (short) axis (Figure 26.2C), orientate the probe so that ventral structures are on the left side of the screen and dorsal structures are on the right (Figure 26.2D).

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Figure 26.2    Probe orientation. (A) This image shows orientation of probe for obtaining longitudinal view. (B) Position the probe so the distal aspect of the neck is on the left side of the screen and the proximal aspect is on the right. (C) This image shows orientation of probe for cross-sectional view. (D) Position the probe so the ventral aspect of the neck is on the left side of the screen and the dorsal is on the right.

Structures visualized when scanning the neck include major blood vessels (jugular veins and carotid arteries), parotid salivary glands, guttural pouches, thyroid glands, lymph nodes, esophagus, trachea, and muscle (Figure 26.3). All structures are bilateral, except for the esophagus, trachea, sternohyoideus muscle, and sternothyroideus muscle, so suspect images can be compared to the opposite side assuming a lesion or abnormality is unilateral.

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Figure 26.3    The main ultrasound sites and associated structures in the neck. This picture illustrates areas on the neck to obtain images of the parotid gland, lymph nodes, thyroid gland, trachea, carotid artery, jugular vein, and esophagus.

Jugular Vein


The jugular vein (Figures 26.4, 26.5, 26.6, 26.7, 26.8, 26.9, 26.10, 26.11) is visible in the jugular groove, from the mandibular branch to the thoracic inlet. Normally, it is thin walled and easily compressible with the ultrasound probe. The blood inside the jugular vein has a hyperechoic, swirling appearance when compared to blood in the adjacent carotid artery. The distal part of the vein should be compressed to dilate the proximal portion of the vessel being scanned to aid in correctly visualizing all the structures, including the valves of the vein. Valves are normal structures that can easily be confused with a small thrombus. Valves appear as thin structures adjacent to the walls of the vessel and move in synchrony with blood flow.

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Figure 26.4    Jugular vein. This image is a cross-sectional view of the left jugular region obtained from a normal adult horse. The jugular vein (3) has been occluded in the distal cervical region. Therefore, the jugular vein remains distended when pressure is applied from the ultrasound probe. The blood inside the vein has a hyperechoic, swirling appearance. The carotid artery (2) is deeper than the jugular vein and the blood has a hypoechoic appearance. The trachea (1) is on the median axis. This sonogram was obtained with a wide-bandwidth 10.0 MHz linear array transducer, operating at 12.0 MHz, at a display depth of 6 cm.
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Figure 26.5    Jugular vein. These images are (A) cross-sectional and (B) longitudinal views of the left jugular region from a normal adult horse. Valves (1) are visualized adjacent to the vessel wall. The carotid artery (2) is deep to the jugular vein. This sonogram was obtained with a wide-bandwidth 6.6 MHz micro-convex linear array transducer, operating at 8.0 MHz, at a display depth of 5 cm.
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Figure 26.6    Jugular vein. This image is a longitudinal view of the left jugular region obtained from a normal adult horse. The carotid artery (1) is deep to the jugular vein (2). The jugular vein has a thin wall, while the carotid artery has a thick wall. Blood in the carotid artery is hypoechoic, while blood in the jugular vein is hyperechoic and swirling. This sonogram was obtained with a wide-bandwidth 10.0 MHz linear array transducer, operating at 12.0 MHz, at a display depth of 5 cm.
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Figure 26.7    Jugular vein. These images are (A) longitudinal and (B) cross-sectional views of the left jugular region from an adult horse with an intravenous catheter. The intravenous catheter (1) is visualized in the lumen of the jugular vein (2). This sonogram was obtained with a wide-bandwidth 10.0 MHz linear array transducer, operating at 12.0 MHz, at a display depth of 5 cm.
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Figure 26.8    Jugular vein. These images are (A) cross-sectional and (B) longitudinal views of the left jugular vein from an adult horse with an intravenous catheter. A hyperechoic clot (2) with well defined margins is visible inside the jugular vein (1). The carotid artery (3) is visualized deep to the jugular vein. These sonograms were obtained with a wide-bandwidth 10.0 MHz linear array transducer, operating at 12.0 MHz, at a display depth of 4 cm.
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Figure 26.9    Jugular vein. This picture is of a clinical case of right jugular phlebitis with a draining track.
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Figure 26.10    Jugular vein. These images are cross-sectional views from proximal (A) to distal (D) of the right jugular region obtained from the clinical case in Figure 26.9. A well demarcated, hyperechoic clot (1) is visible inside the jugular vein (2).
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Figure 26.11    Jugular vein. These images are longitudinal views from proximal (A) to distal (B) of the right jugular region obtained from the clinical case in Figure 26.9. A draining track (1) is visible coming from the jugular vein (2). These sonograms were obtained with a wide-bandwidth 10.0 MHz linear array transducer, operating at 12.0 MHz, at a display depth of 4 cm.

Ultrasound of the jugular vein can confirm correct placement of an intravenous catheter in the vessel lumen and may aid in detecting early signs of thrombus formation associated with the catheter, although thrombi may also form in the jugular vein in the absence of an intravenous catheter or any other known trauma to the vessel. Thrombi appear as hyperechoic structures in the vessel lumen or attached to the vessel wall. Margins may be smooth and well demarcated or pedunculated in appearance. If an intravenous catheter is in the vein, a fibrin envelope or sleeve may be visualized around the catheter before a thrombus forms [1]. Initially, blood flow is maintained, but the thrombus may increase in size to cause inflammation of the vessel (thrombophlebitis) and, potentially, complete occlusion of the vessel. Other changes associated with thrombophlebitis include perivasculitis of the surrounding soft tissue and thickening of the vessel wall [1].


Carotid Artery


The carotid artery (Figures 26.4, 26.5, 26.6, 26.8) is visible in the jugular groove medial to the jugular vein and lateral to the trachea. The wall is thicker than that of the jugular vein and the vessel is not compressible. The blood is hypoechoic compared to blood in the jugular vein. In the proximal neck, the carotid artery is separated from the jugular vein by the omohyoideus muscle, but in the middle and distal neck, the muscle thins and the carotid artery and jugular vein are in close proximity to each other.


Guttural Pouches


The guttural pouches are ventral diverticula of the eustachian tube and extend from the nasopharynx to the middle ear. They contain air and have a capacity of 300–500 ml in adults. These structures are usually not detectable by ultrasound examination except in the diseased state.


Guttural pouch tympany (Figure 26.12) occurs in young animals, usually less than 1 year of age, when the plica salpingopharyngea, the flap of tissue covering the pharyngeal opening, fails to let air escape the guttural pouch. With the flap functioning as a one-way valve, the pouch fills with air. Some cases are mild, while others progress to respiratory distress from occlusion of the pharyngeal area from the distended guttural pouch [2].

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Figure 26.12    Guttural pouch tympany. (A) This picture is of a 3-month-old Arab Thoroughbred filly with guttural pouch tympany. The foal had marked distension of the throatlatch region, was in respiratory distress, and required an emergency tracheostomy. The percussion exam revealed a tympanic sound in the upper part of the enlargement and a dull sound in the lower part. (B) This image is a longitudinal view of the right parotid and laryngeal region. A well defined distinction between the upper (2) and the lower (1) portion of the right guttural pouch is evident. The upper portion is filled with air (2) that casts a typical reverberation artifact. The lower portion is filled with mucus (1) that has a mildly echogenic appearance that is not homogeneous. This sonogram was obtained with a wide-bandwidth 5.0 MHz linear array, transrectal transducer, operating at 5.0 MHz, at a display depth of 4 cm.

Guttural pouches may contain exudate or chondroids (inspissated pus) with guttural pouch empyema (Figures 26.13, 26.14). Empyema may occur secondary to any respiratory disease, but infection with Streptococcus equi is a common finding. The pouches may contain blood if trauma occurs to any structure associated with the guttural pouch. A common finding in guttural pouch trauma and hemorrhage is fracture of the stylohyoid bone. Another cause of blood in the pouch is guttural pouch mycosis. A fungal plaque forms in the pouch and causes erosion of a blood vessel, usually the internal carotid artery, resulting in hemorrhage into the guttural pouch.

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Jun 8, 2017 | Posted by in EQUINE MEDICINE | Comments Off on TWENTY-SIX: Ultrasonography of the Soft Tissue Structures of the Neck

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