DIAGNOSTIC IMAGING


to the structures caudal to the mandible (parotid salivary gland, branches of the carotid artery) and from the underlying main carotid artery, esophagus, and trachea along the course of the neck.


3. Results


Normal jugular veins appear to be collapsed, with thin echolucent regions of blood flow without some distal occlusion to interrupt blood flow and allow for maximal distension of the vein lumen. Normal dis- tended jugular veins will appear as rounded tubes of echolucent fluid (blood) within the lumen and thin, echogenic walls with distinct margins of the endo- thelial surface (Fig. 1). The blood column within a normal vein that has been occluded will, on some occasions, begin to swirl and provide a variably echo- genic laminar appearance (Fig. 2). In the author’s practice, swelling or pain around


the intravenous catheter insertion site are consid- ered indications for ultrasound imaging of the jugu- lar vein. In addition, distension of the vein or its proximal branches with or without unilateral facial edema or trauma to the neck region might also be indications for scanning the jugular vein. Common problems that can be identified with ultrasound imaging of the jugular vein include de- tection of perivascular inflammation, localized or extensive thrombophlebitis, differentiation of septic thrombophlebitis from thrombosis alone, and early detection of catheter-associated thrombosis. Perivascular inflammation (Fig. 3)—associated


with intravenous injection or catheter placement— can result in swelling and thickening of the perivas- cular tissues, whereas the lumen of the jugular vein remains unaffected. This finding would usually in- dicate that topical local therapy—anti-inflammatory and/or topical antimicrobial agents—might be suffi- cient in resolving the thickening. Occasionally, an aberrant injection of material into the adjacent perivascular tissues or surrounding musculature might occur, and this can be demonstrated and mon- itored with the use of ultrasound. Varying degrees of thrombosis within the jugular


vein lumen (Fig. 4) can be identified, from focal/ regional involvement to more progressive thrombo- sis with complete luminal obstruction that can extend along the entire course of the jugular vein within the neck. A thrombus will appear as a vari- ably echogenic, variably shaped solid material within the lumen of the vein. Often, the thrombus will appear to be attached to the endothelial surface of the vein at a site of catheter entry or as a sheath along an indwelling intravenous catheter or at- tached to a site of previous injection or catheteriza- tion. The margins may appear irregular and indistinct (“fuzzy”), as with recent or active throm- bus formation, or smooth with thrombi of longer duration in which blood flow has formed the mar- gins. Occasionally, a jugular thrombus of longer duration will have a cone shape to its distal margins.


208 2013  Vol. 59  AAEP PROCEEDINGS


Longitudinal images (Fig. 5) are useful for determin- ing the linear involvement along the course of the jugular vein. Acute thrombosis can undergo repair by fibrinolysis to varying degrees of recanalization, or it can evolve to organization into chronic fibrous resolution with complete obstruction of the vein lu- men (Fig. 6). Thrombosis can occur with repeated intravascular injections, iatrogenic trauma on attempting to inject the jugular vein of a fractious horse, or after injec- tion by an unskilled individual. Thrombosis has also been reported to occur as a sequel to other sites of infection, unrelated to venipuncture or catheter- ization.2 Once thrombosis of the jugular vein has been identified, ultrasound imaging can be useful in monitoring the clinical progression or resolution of the lesion. In addition to detection of thrombosis, ultrasound


is also useful for detecting changes consistent with septic thrombophlebitis as well as determining the location and extent of inflammatory exudate within the vein. Septic thrombophlebitis is usually ob- served as varying regions of densely echogenic ma- terial within the thrombus (Figs. 7 and 8). Finding this echogenic focus can allow for ultrasound-guided aspiration to obtain a sample of the exudate for bacterial culture and sensitivity and possibly drain- age of the exudate.


4. Discussion


Ultrasound imaging is a useful tool for evaluation of a variety of changes along the jugular vein. It can aid in differentiation of the anatomic location of swellings in the jugular groove—whether the change is within the jugular vein or from in- volvement of the perivascular tissues. Commonly differentiated changes include perivascular inflam- mation, jugular thrombosis over the spectrum of acute-to-chronic and focal-to-extensive involvement of the vein, and detection of changes consistent with septic exudate within the thrombus or in the perivascular tissues. Early detection and interven- tion for thrombosis, whether from injections or as- sociated with intravenous catheter placement, can improve clinical outcomes and may help to reduce costs of medical management. Ultrasound imaging is vital in the detection of sites of sepsis within the venous thrombus. The technique for ultrasound imaging of the jugular vein is relatively easy and involves the use of readily available ultrasound equipment in most equine practices.


References


1. Hussini CA, Barbosa RG, Borghesan AC, et al. Equine experimental thrombophlebitis: clinical, ultrasonographic, and venographic evaluation. Pesquisa Veterarinia Brasil- eira. 2012;32:595–600.


2. Matsuda K, Suzuki H, Tsunoda N, et al. Jugular thrombo- phlebitis developed from buccal ulcer in a Thoroughbred horse. J Vet Med Sci. 2010;72:913–915.


3. Reef VB. Equine Diagnostic Ultrasound. Philadelphia: WB Saunders and Co; 1998:265–267.


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