Visualization of the Thoracic Duct with Injections of Dyes or Contrast Media into the Testicular Parenchyma in the Rabbit

Abstract

ABSTRACT. The thoracic duct drains lymph from the caudal part of the body to the venous system. The visualization of the thoracic duct is important for diagnosis of chylothorax, which may be caused by the damage of the duct. However, it is not easy to visualize the thoracic duct by injecting dyes and/or contrast media into peripheral lymph nodes and mesenteric lymphatics. In the present study, we examined whether the thoracic duct can be visualized by injecting dyes and contrast media directly into the testicular parenchyma. Under deep pentobarbital anesthesia, 14 male Japanese White rabbits were percutaneously injected with dyes (India ink or methylene blue) or contrast media (iohexol 240, 300, or Lipiodol TM ) into the testicular parenchyma. Then, we grossly observed the stained thoracic duct or took radiographs and CT images of the duct. In all cases with dyes injections, the thoracic duct was successfully visualized. We observed stained lymphatic vessels from the testis to the duct. In case of contrast media injections, the thoracic duct was visualized with X-ray and CT imaging, when 1.5-2.0 ml per one testis of iohexol 240 at 37C were injected into the right or both testes. The duct was most clearly visible, 3-5 min after the injections. The results show that the thoracic duct is reliably visualized simply by injecting dyes or contrast media into the testicular parenchyma. Our visualization method may also be applicable to the diagnosis of chylothorax in male animals. The thoracic duct is the main lymphatic channel that drains lymph from the caudal part of the body to the venous system. The damage of the thoracic duct causes chylothorax that is characterized by accumulation of chyle in the pleural cavity. In such cases, the visualization of the thoracic duct is important for diagnosis and treatment of chylothorax in veterinary practice [3,4].To visualize the thoracic duct, dyes such as India ink (for anatomical purpose) and methylene blue (MB) or X-ray contrast media have been injected into the mesenteric, inguinal, popliteal, and metatarsal lymph vessels [1,3,8] or the mesenteric, popliteal, and axillary lymph nodes [5,9,12]. However, except for the popliteal lymph node, surgery is required to approach these nodes and vessels, before injections of dyes or X-ray contrast media. Furthermore, technical skills are also needed, when injections are made into these thin lymphatics especially in small dogs and cats. An alternative, less invasive method is injections of dyes or contrast media into the popliteal lymph nodes. However, it has been reported that popliteal injections visualize the thoracic duct less reliably than mesenteric injections [5].Recent studies have shown that the testicular efferent and abdominal lymphatics were visualized by injections of dyes such as patent blue violet and India ink or X-ray contrast media such as ethyl ester of iodinated poppy-seed oil fatty acid into the testicular parenchyma in the rat [2,10]. The results of these studies suggest the possibility that the thoracic duct co...

Visualisation of the thoracic duct after popliteal lymph node injection in the pig: comparison of radiographic and thoracoscopic techniques

“…It is thought that high-viscosity products have difficulties flowing through narrow lymph vessels. Tsuruno et al (2009) concluded that iohexol-240 is an optimal agent for TD visualisation in rabbits after intratesticular injection. As iohexol-240 is unregistered in our country, we used iohexol-350 (diluted in saline) to obtain a 245 mg/ml solution.…”

“…Ashitate et al (2011) observed that MB injection into an inguinal LN resulted in successful TD visualisation in all pigs (8/8). When India ink or MB was injected in the testicular parenchyma of rabbits, TD was visualised in 3/3 patients (Tsuruno et al 2009). …”

“…Allman et al (2010) injected meglumine diatrizoate into a mesenteric lymphatic vessel and obtained a positive TD lymphangiographic study in only one out of three dogs, whereas Leasure et al (20111) visualised the TD in six out of six dogs after injection of meglumine and sodium diatrizoate into a mesenteric lymphatic vessel. Tsuruno et al (2009) injected iohexol into the testicles of rabbits. Visualisation of the TD was obvious in five out of nine patients (those where 240 mg/ml iohexol was used at 37°C).…”

“…It can be hypothesised that dilution actually reduces the viscosity and should have improved the flow. Also, warming the contrast media to a temperature of 37 °C improved the flow rate of contrast medium after intratesticular injection in rabbits, as increasing the temperature of a fluid reduces its viscosity (Tsuruno et al 2009). In our study, iohexol was injected at room temperature (26 °C); we suspect that better results would have been obtained after warming the contrast agent.…”

Patterns of Efferent Lymphatics of the Rabbit Testis

“…This implies that the courses of efferent lymphatics may have a unique pattern in this species. Thus, we examined the patterns of courses of efferent lymphatics originating from the rabbit testis, by injecting India ink directly into the testicular parenchyma [11].…”