Anatomic and volumetric characterization of the cisterna chyli using CT lymphangiography and computer‐assisted design software in dogs with idiopathic chylothorax

The objectives of this retrospective, observational study were to characterize the anatomical features of the cisterna chyli (CC) in a cohort of dogs diagnosed with idiopathic chylothorax that underwent CT lymphangiography (CTLa), and to evaluate the feasibility of computer‐assisted design (CAD) software to quantify volumetric measurements of the CC. Twenty‐three client‐owned dogs with idiopathic chylothorax were included. Additionally, CTLa was performed in three canine cadavers to assess the ability of CAD software to accurately acquire volumetric measurements. Injection sites, attenuation values, anatomic location, dimensions, and aortic diameter to CC ratio (Ao:CC) were recorded. Video records of video‐assisted thoracic surgery (VATS) thoracic duct ligation (TDL) were reviewed in eight out of 23 dogs to compare operative and CTLa findings. The CC was dorsal and right‐sided in 18 out of 23 dogs, located between L1 and L4 in 21 dogs, and extended as far cranially as T11 in two dogs. The median measurements for length, height, and width were 150.0, 5.5, and 13.3 mm, respectively. Median total volume was 1.82 mL. Median volumes to the right and left of the aorta were 1.46 and 0.49 mL, respectively (P = .014). Median total CC volume to body weight ratio (CC:bw) was 0.07 mL/kg. The presence of an intrathoracic CC was observed intraoperatively in six out of eight cases that underwent VATS TDL. Findings supported the use of CTLa and CAD as feasible methods for characterizing the CC in dogs diagnosed with chylothorax. These methods may facilitate interventional planning involving the CC such as embolization.     

ULTRASONOGRAPHIC CHARACTERISTICS OF THE CISTERNA CHYLI IN EIGHT DOGS AND FOUR CATS

Ultrasonography of the cisterna chyli has been used in humans to diagnose increased lymphatic flow or lymph flow obstruction and to guide percutaneous embolization of the thoracic duct via the cisterna chyli. The aim of this study was to describe the ultrasonographic characteristics of the dorsal portion of cisterna chyli in dogs and cats with chylous ascites or chylothorax and in a group of healthy dogs and cats. The aorta and the cranial mesenteric artery were used as anatomic landmarks. Ultrasonography was performed before and 2 h after a fatty meal in healthy dogs and cats. The visualized structure was confirmed to be a dilated cisterna chyli at necropsy in a dog with chylous ascites. The confirmed or presumed cisterna chyli was consistently detected using ultrasonography in nonfasted healthy animals and clinically affected animals and appeared as an anechoic tubular structure, without detectable flow, at the right dorsolateral aspect of the aorta. It had a similar ultrasonographic appearance in patients with chyloabdomen and in nonfasted healthy dogs and cats. There was considerable overlap in diameters of the cisterna chyli for affected and healthy animals. The shape and size of the cisterna chyli in an individual animal were variable during the same ultrasound examination and between different examinations. This study demonstrated the appearance of the presumed dorsal portion of the cisterna chyli by ultrasonography and might provide useful preliminary data for further studies into the feasibility of ultrasound‐guided injections or aspirations of the cisterna chyli in dogs and cats.     

Computed Tomographic Lymphography of the Thoracic Duct by Mesenteric Lymph Node Injection

Objective— To document a novel technique to image the thoracic duct and its tributaries by contrast enhanced computed tomography (CT) lymphography.
Study Design— Clinical report.
Animals— Dogs (n=6) idiopathic chylothorax.
Methods— Ultrasonography was used to guide percutaneous injection of intestinal lymph nodes with nonionic iodinated contrast medium for preoperative CT lymphography of the thoracic duct in 6 dogs with chylothorax. Thoracic CT images were acquired immediately after contrast medium injection. All dogs had subtotal pericardectomy and thoracic duct ligation. Postoperative thoracic duct lymphography was performed in 3 dogs. Superficial cervical lymph node lymphography was performed in 2 dogs to determine cervical lymphatic contribution to thoracic effusions.
Results— Preoperative thoracic duct lymphography using this technique was successful in delineating the cisterna chyli, thoracic duct, and associated lymphatic vessels in all dogs. Immediate postoperative lymphography performed in 2 dogs revealed successful duct ligation in 1 dog and persistent lymphatic leakage in the other. A 1-month postoperative thoracic duct lymphogram performed in 1 dog revealed unsuccessful ligation or recannulation of 1 of 3 redundant vessels seen preoperatively.
Conclusion— Percutaneous CT lymphography results in excellent detection of the thoracic duct and abnormal thoracic duct drainage patterns both pre- and postoperatively. The contribution of superficial cervical lymph node drainage to reoccurrence of effusions can be evaluated.
Clinical Relevance— Percutaneous CT lymphography using ultrasound-guided contrast medium injection should be considered as an alternative to conventional open abdominal approaches to radiographic or CT lymphography.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF THE CISTERNA CHYLI IN DOGS

Previous lymphangiographic studies have investigated the use of computed tomography (CT) for characterizing the thoracic duct and its tributaries in dogs. However, there is limited published information on the appearance of the canine cisterna chyli using CT. The objective of this retrospective study was to describe the features of the canine cisterna chyli in pre‐ and post‐contrast abdominal CT studies. The presence, location, shape, maximum width, size compared with the aortic diameter (Ao:cisterna chyli ratio) and mean attenuation of the cisterna chyli were recorded from archived abdominal CT scans of 30 dogs. Breed, age, sex and neutering status were also noted. A cisterna chyli was identified in 26 of the dogs (87%). In 22 cases a cisterna chyli could be reliably identified prior to intravenous contrast administration and in all 26 cases in postcontrast images. The cisterna chyli was most commonly located right dorsolateral to the abdominal aorta between L1 and L4. Shape varied on transverse images from crescent‐like to globular and maximum diameters ranged from 5 to 9 mm. The Ao:cisterna chyli ratio varied between 0.29 and 0.71 (mean value—males: 0.32; females: 0.38). On pre‐contrast images the mean Hounsfield units were 21.3HU (range: –3.8 to 64.25). Mild enhancement of the cisterna chyli post‐contrast was observed in 24 dogs (80%). Findings supported the use of pre‐ and post‐contrast abdominal CT as a non‐invasive method for assessing qualitative and quantitative characteristics of the canine cisterna chyli.     

Cisterna chyli ablation with thoracic duct ligation for chylothorax: results in eight dogs

OBJECTIVE: To report use of combined cisterna chyli ablation (CCA) and thoracic duct ligation (TDL) for treatment of spontaneously occurring chylothorax in dogs. STUDY DESIGN: Retrospective study. ANIMALS: Eight dogs with chylothorax. METHODS: TDL was performed through a right caudal intercostal thoracotomy and CCA through a left flank paracostal approach or ventral median celiotomy. Long-term outcome (range, 2-48 months; median, 11.5 months) was evaluated by telephone communication with owners. RESULTS: Seven dogs were free of clinical signs related to chylothorax at last follow-up (range, 4-48 months; median, 15.5 months). One dog was euthanatized 2 months after surgery because of lack of improvement. No major complications occurred from CCA. CONCLUSION: CCA and TDL resolved chylothorax in most dogs (88%). CLINICAL RELEVANCE: CCA combined with TDL may improve the outcome of chylothorax in dogs.     

MAGNETIC RESONANCE IMAGING APPEARANCE OF THE CISTERNA CHYLI

Thoracolumbar spinal magnetic resonance imaging (MRI) examinations in dogs frequently include the region of the cisterna chyli within the field of view. It is important to be aware of the appearance and location of this structure to avoid confusing it for a pathologic periaortic lesion. MRI examinations of the thoracolumbar spine were reviewed in 30 dogs. The cisterna chyli was identified in 26 dogs and was most commonly located caudal to the diaphragmatic crura at the level of L4; afferent and efferent lymphatics were seen in all dogs. Transverse T2-weighted images were the most useful to locate the cisterna chyli. It was isointense to fluid on T2-weighted images and isointense to muscle on T1-weighted images. Mild contrast enhancement was seen in three dogs. The cisterna always wrapped around the aorta, but varied in shape, with the most common being the wide right dorsolateral ellipse. The thoracic duct was also visible in 30 dogs. MRI may have potential for noninvasive evaluation of the abdominal and thoracic lymphatic ducts in dogs.     

Comparison of Computed Tomographic and Radiographic Popliteal Lymphangiography in Normal Dogs

Objective: To (1) describe computed tomographic (CT) popliteal lymphangiography; (2) compare the number of thoracic duct (TD) branches detected by CT and by radiography after popliteal lymphangiography; and (3) to compare the number of branches detected after left and right popliteal lymphangiography. Study Design: Experimental study. Animals: Adult dogs (n=6). Methods: A randomly selected popliteal lymph node was percutaneously injected with 12 mL iodinated contrast medium through a 25‐g butterfly catheter over 4–5 minutes. Lateral and ventrodorsal (VD) thoracic radiograph projections and thoracic CT were performed. The procedure was repeated using the contralateral lymph node after a 48–72 hours washout period. Results: One dog had TD branches visible on CT but not on radiographs. A significantly greater number of TD branches were observed with CT popliteal lymphangiography compared with lateral and VD radiographic popliteal lymphangiography (P=.003 and P<.001, respectively). The number of visible TD branches observed between the 6th thoracic and 1st lumbar vertebrae were not significantly different in these dogs (P=.146). A significant difference in number of TD branches observed was not found after left or right popliteal lymph node injection (P=.097). Conclusions: CT popliteal lymphangiography consistently identified a greater number of TD branches when compared with radiographic popliteal lymphangiography. Injection of either popliteal lymph node resulted in the same number of TD branches being observed.     

The effect of cisterna chyli ablation combined with thoracic duct ligation on abdominal lymphatic drainage

OBJECTIVE: To evaluate the effect of cisterna chyli ablation (CCA) and thoracic duct ligation (TDL) on abdominal lymphatic drainage in normal dogs. STUDY DESIGN: Experimental study. ANIMALS: Nine female beagle dogs. METHODS: TDL was performed in 3 dogs and was combined with CCA (CCA-TDL) and local omentalization in 6 dogs. Contrast lymphangiography was attempted in all dogs immediately before and after TDL. Dogs were reanesthetized at 31-37 days for lymphatic studies by new methylene blue (NMB) injection into a mesenteric lymph node and by contrast lymphangiography. RESULTS: In 6 CCA-TDL dogs, 2 had direct shunting of contrast from the lymphatic system into major abdominal veins, 3 had contrast material that dissipated into abdominal vessels within the mesenteric root, and 1 had shunting into the azygous vein. NMB was not observed within the omental pedicle after CCA-TDL. Chylous drainage was by the azygous vein in all 3 TDL dogs. CONCLUSIONS: CCA-TDL disrupted chylous drainage to the thoracic duct and resulted in direct intraabdominal lymphaticovenous anastomoses identified by shunting of lymphatic flow directly into the abdominal vasculature in 5 of 6 CCA-TDL dogs. Omentalization of the cisternal ablation site was not beneficial in augmenting extrathoracic lymphatic drainage and is not recommended with CCA-TDL. CLINICAL RELEVANCE: CCA-TDL represents a novel approach to surgical redirection of chylous drainage to the venous circulation outside of the thorax and may be useful in the treatment of spontaneous chylothorax in the dog.     

Lymphography of the thoracic duct by percutaneous injection of iohexol into the popliteal lymph node of dogs: experimental study and clinical application

OBJECTIVE: To evaluate the efficacy of percutaneous administration of iohexol into the popliteal lymph node as a non-invasive technique for thoracic duct lymphangiography in dogs. STUDY DESIGN: Experimental study and clinical report. ANIMALS: Normal adult dogs (n=4) and 1 dog with recurrent chylothorax. METHODS: For the experimental study, 4 dogs (weight, 8.4-12.3 kg) had 5-10 mL iohexol injected percutaneously into 1 popliteal lymph node and then thoracic radiographs were taken. Popliteal lymph nodes were examined by histopathology 8 days later. One 25-kg dog with recurrent chylothorax had 25 mL iohexol injected into the right popliteal lymph node followed by thoracic radiography. RESULTS: In experimental dogs, the thoracic duct was best visualized on thoracic radiographs after administration of 10 mL iohexol. Clinically, no abnormalities were identified in the injected limb and except for 1 dog that had large numbers of siderocytes and erythrophagocytic macrophages in the injected lymph node, the histopathologic findings in the other injected popliteal lymph nodes were not different from contralateral nodes. In the clinical case, the thoracic duct was visualized, but there was leakage of iohexol around the node. CONCLUSION: The thoracic duct in dogs can be visualized by lymphography after percutaneous injection of iohexol (1 mL/kg at 2 mL/min) into the popliteal lymph node. CLINICAL RELEVANCE: Percutaneous popliteal lymph node administration of iohexol should be considered as an alternative to mesenteric lymph node injection for radiographic identification of the thoracic duct in dogs.     

Lymphangiographic evaluation of experimentally induced chylothorax after ligation of the cranial vena cava in dogs

Ligation of the cranial vena cava (CrVC) distal to the entrance of the azygous vein resulted in chylothorax in 7 of 10 dogs. Of the remaining 3 dogs, 1 developed a serosanguineous effusion that did not become chylous, and 2 dogs did not develop pleural effusion. In 2 of the 7 dogs developing chylothorax, the pleural effusion became serosanguineous within 2.5 weeks after CrVC ligation. Mesenteric lymphangiography was performed 2 to 6 weeks after ligation of the CrVC. Lymphangiectasia was seen in 4 dogs with chylothorax, but was not seen in the 3 dogs with serosanguineous effusions or the 2 dogs that did not develop effusions. One dog with chylothorax died prior to repeat lymphangiography. Less dye entered the thoracic duct, and alternate lymphaticovenous communications to the caudal vena cava were evident in the dogs without chylothorax. Ligation of the thoracic duct at the lymphaticovenous junction was performed in 3 dogs. These dogs did not develop pleural effusion. Lymphangiography was performed immediately after ligation and indicated filling of abdominal lymphatics but not of the thoracic duct. Lymphangiographic findings 6 weeks after ligation also indicated filling of intestinal lymphatics. Results of the present study indicated that ligation of the CrVC causes chylothorax, and that thoracic lymphangiectasia is a consistent finding in animals with experimental chylothorax. Obstruction of the thoracic duct did not induce lymphangiectasia or chylothorax. Impedence of thoracic duct flow into the CrVC may be a cause of clinical chylothorax in the dog.     

Chylothorax in cats: 37 cases (1969-1989)

Case records of 37 cats with chylothorax examined at 2 institutions were retrospectively evaluated. Dyspnea and coughing were the most common abnormalities noticed by the owners, and most cats were dyspneic on initial examination. There was no statistically significant difference in the gender distribution of cats studied when compared with reference populations; however, purebred cats appeared to be overrepresented in the study population. Four of the cats had unilateral pleural effusion (2 left side, 2 right side) and 9 cats had effusions that were primarily, but not exclusively, on the right side. Surgery was performed on 20 cats. Fifteen cats underwent thoracic duct or cisterna chyli ligation; 20% had complete resolution of pleural fluid. There was no significant difference in the survival rate of cats that underwent thoracic duct ligation and those that were treated by other means. Six cats had mesenteric lymphangiography performed; 2 cats had normal results, and the remainder had various degrees of thoracic lymphangiectasia. Two cats in which pleuroperitoneal shunts were placed and 2 of 3 cats that underwent pleurodesis were euthanatized or died after surgery.     

Transcatheter Thoracic Duct Embolization in the Dog An Experimental Study

Thoracic duct embolization was created by injecting an isobutyl 2-cyanoacrylate/iophendylate (IBCA) mixture through a cannulated mesenteric lymphatic vessel in eight normal dogs. Aqueous contrast lymphangiography was repeated at minute 10 and week 6. Six dogs were euthanatized at week 6 and two dogs at month 6. Embolization with 1.5 to 3.9 ml of the mixture resulted in complete obstruction of the thoracic duct in all eight dogs. Results of lymphangiography in six dogs at week 6 showed a persistent, complete obstruction of the thoracic duct in six dogs and alternate lymphaticovenous anastomoses in four dogs. Histologically, there were a sclerosing granulomatous response surrounding the lymphatic embolus, mild congestive changes in the mesenteric lymph nodes, and mild lacteal dilatation in the jejunum. The procedure was well tolerated with only a few complications. One dog suffered partial thrombosis of the cranial vena cava by the injected material with later dislodgement and embolization of a pulmonary artery branch. Modifications have been made in the injection procedure to avoid this complication. This technique for occlusion of the thoracic duct shows potential for clinical use in the management of canine chylothorax. The obstruction appears to be complete and permanent, and surgical/anesthetic time is decreased greatly from previously described procedures.     

Popliteal and mesenteric lymph node injection with methylene blue for coloration of the thoracic duct in dogs

OBJECTIVE:To describe and compare the time of onset and intensity of thoracic duct coloration after injection of methylene blue into a mesenteric or popliteal lymph node. STUDY DESIGN: Experimental study. ANIMALS: Twenty adult dogs. METHODS: A right tenth intercostal thoracotomy, a right paracostal laparotomy, and an approach to the right popliteal lymph node were performed on each dog. Methylene blue (0.5 mg/kg of a 1% solution, maximum 10 mg) was injected into either a mesenteric (group M, 10 dogs) or popliteal (group P, 10 dogs) lymph node. Thoracic duct color was graded (0 to 3) every 5 minutes for 60 minutes. Statistical analysis was performed on mean thoracic duct color grade data, on number of successful outcomes between groups M and P, and between weight groups. RESULTS: Coloration of the thoracic duct occurred in all group M dogs and 6 group P dogs. Coloration was first recorded 0 to 10 minutes after injection in all dogs and persisted for 60 minutes in 15 dogs. Mean thoracic duct color grade was significantly increased postinjection compared with preinjection at all times in group M. More successful outcomes occurred in group M (P =.03). CONCLUSIONS: Methylene blue injected into mesenteric or popliteal lymph nodes was successful in coloring the thoracic duct, but both mean grade and number of successful outcomes were significantly higher after mesenteric injection. CLINICAL RELEVANCE: Thoracic duct coloration after lymph node injection occurred within 10 minutes and persisted for 60 minutes. This information is useful in planning thoracic duct ligation in cases of chylothorax when observation of the duct is desired. Injection of both lymph node sites was successful, but mesenteric node injection was a more reliable technique.     

Thoracic duct ligation and pericardectomy for treatment of idiopathic chylothorax

Chylothorax is a devastating disease, and the success rates from either medical or surgical management are less than satisfactory. In some animals with chylothorax, a thickening of the pericardium occurs that is associated with chronic irritation induced by chyle. We hypothesized that pericardial thickening would lead to increased right-sided venous pressures and that abnormal venous pressures would act to impede the drainage of chyle via lymphaticovenous communications after thoracic duct (TD) ligation. We also hypothesized that serosanguineous effusions that occurred after TD ligation could effectively be treated or prevented by pericardectomy in affected animals. TD ligation plus pericardectomy was performed in 17 animals, and pericardectomy alone was performed in an additional 3 animals that presented during a 5.5-year period to the Texas A&M University (College Station, TX). Nineteen animals presented for an evaluation of idiopathic chylothorax (9 dogs and 10 cats), and 1 dog presented for serosanguineous pleural fluid after TD ligation that had been performed elsewhere. Echocardiography was normal in all animals, except for a subjectively thickened pericardium in 7 cats and 6 dogs. Clinical signs of pleural fluid accumulation resolved in 10 of 10 dogs and in 8 of 10 cats after surgery. The overall success rate for the surgical treatment of chylothorax (ie, the resolution of pleural fluid accumulation) in this study was 90% (100% in dogs and 80% in cats). These data suggest that TD ligation in conjunction with pericardectomy has a favorable outcome in animals with idiopathic chylothorax.     

Chylous ascites in three dogs.

Chylous ascites was diagnosed in 3 dogs. Mesenteric lymphangiography was performed in 2 dogs and helped delineate abnormalities of the lymphatic system. The cause of chylous ascites in each dog appeared to be different. In 1 dog, a ruptured mesenteric lymphatic was identified at surgery. Evidence of abdominal lymphatic obstruction was found in another dog. Chylous ascites in the third dog appeared to be a complication of mesenteric lymphangiography for chylothorax.     

Radiographic lymphangiographyin the dog using iodized oil

The objective of this study was to develop a clinically applicable technique to visualize the medial retropharyngeal, superficial cervical, axillary, superficial inguinal and medial iliac lymph nodes on radiographs. Direct and indirect lymphangiographic methods using iodized oil were repeated for a minimum of five times at eight different locations to enhance the various lymph nodes, using 16 healthy research dogs. Direct lymphangiography, although more invasive than indirect lymphangiography, resulted in uniform contrast uptake by an increased number of nodes and increased enhancement of the lymphatic vasculature, and is recommended for imaging the medial iliac and superficial cervical lymph nodes. Side effects were more frequent after indirect lymphangiography (10/20 injection sites) than after direct lymphangiography (3/16 injection sites). The small size of afferent lymphatic vessels did not allow use of direct lymphangiography for the medial retropharyngeal, axillary and superficial inguinal lymph nodes; however, indirect techniques allowed adequate visualization of these nodes.     

Anatomical variations of the thoracic duct in the dog

Anatomical variations can be frequently found in the lymphatic system, which is also true for the shape and course of the thoracic duct (ductus thoracicus), the biggest lymph vessel in the body. From 2012 to 2019, the thoracic duct was successfully dissected in 43 dog carcasses that were used in the anatomy course at the Faculty of Veterinary Medicine, University of Zagreb. The thoracic duct originated from the cranial border of the cisterna chyli as one lymph vessel in 36 dogs (83.7%), as two vessels in six dogs (14%) and as three vessels in one dog (2.3%). We divided the observed thoracic duct variations into six groups according to their anatomical similarities. Considering the specific embryonic development, we can conclude that all observed variations are the result of minor deviations from the standard ontogenesis. However, the importance of thoracic duct variations is significant in surgical procedures done in the thoracic cavity to prevent or cure the chylothorax. Since this research showed variations in 39 out of 43 dogs (90.7%) throughout the whole course of the thoracic duct, great care must be taken while performing the ligation or embolization of the thoracic duct.     

Comparison of mesenteric lymphadenography performed via surgical and laparoscopic approaches in dogs

OBJECTIVE: To determine whether injection of a mesenteric lymph node with iodinated aqueous contrast medium results in radiographic delineation of the thoracic duct and its branches, ascertain the ideal interval between injection and radiographic imaging, and evaluate mesenteric lymphadenography performed via laparoscopic and surgical approaches in dogs. ANIMALS: 10 adult dogs. PROCEDURE: In each dog, a right paracostal laparotomy or a right laparoscopic approach was performed to identify a mesenteric lymph node for injection of an iodinated aqueous contrast agent (0.22 mL/kg [81.4 mg of iodine/kg]). Lateral radiographic views were obtained at 60, 120, 180, 240, and 300 seconds after injection. RESULTS: A mesenteric lymph node was identified and injected with contrast medium in each dog. Via paracostal laparotomy, lymph node injection resulted in successful lymphangiographic evaluation in 4 of 5 dogs, whereas via the laparoscopic approach, lymph node injection resulted in successful lymphangio-graphic evaluation in 2 of 5 dogs. In successful radiographic evaluations, injected lymph nodes, mesenteric lymphatics, and the thoracic duct and its branches were delineated. Radiographs obtained at 60 and 120 seconds after injection of contrast medium provided the most detail. CONCLUSIONS AND CLINICAL RELEVANCE: Injection of a mesenteric lymph node directly with contrast medium appears to be a feasible technique for delineation of the thoracic duct and its branches in dogs and might be useful in small animals in which mesenteric lymphatic catheterization can be difficult and lymphangiography is more likely to fail. Refinement of the laparoscopic technique may provide a minimally invasive approach to lymphadenography.     

En bloc ligation of the thoracic duct in twelve dogs with idiopathic chylothorax

Twelve dogs with idiopathic chylothorax were treated by en bloc ligation of the thoracic duct. Six dogs recovered completely. Minimal follow-up in this group was 12 months. Five dogs were euthanized within 5 months of surgery because of persisting liquothorax: two with chylous and three with non-chylous effusions. One dog was euthanized 2 months after surgery because of a recurrence of dyspnoea. It is concluded that the results are comparable with those of a previously described surgical treatment; however, the technique described here is less complicated because it does not require mesenteric lymphangiography.