Transcatheter thoracic duct embolization in the dog. An experimental study

Advances in the Treatment of Chylothorax

Idiopathic chylothorax is a challenging clinical condition historically associated with poor resolution rates following surgical intervention. Recent advances in imaging and surgical techniques have revolutionized the treatment of this disease process. Computed tomographic lymphangiography has facilitated improved surgical planning and postoperative assessment, while intraoperative use of near-infrared fluorescence imaging aids in highly accurate intraoperative thoracic duct identification. Utilizing these advancements, minimally invasive surgical techniques have been successfully developed and have been associated with considerable improvements in surgical outcomes.

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.

Efficacy of en bloc thoracic duct ligation in combination with pericardiectomy by video-assisted thoracoscopic surgery for canine idiopathic chylothorax

OBJECTIVE

To compare the outcomes of pericardiectomy performed with conventional clipping thoracic duct ligation (C-TDL) to those with en bloc thoracic duct ligation (EB-TDL) using video-assisted thoracoscopic surgery (VATS) for canine idiopathic chylothorax.

STUDY DESIGN

Retrospective consecutive case series.

ANIMALS

Thirteen client-owned dogs with idiopathic chylothorax.

METHODS

Medical records of dogs treated with pericardiectomy in combination with TDL by VATS without intraoperative contrast were reviewed. Five and seven dogs underwent C-TDL and EB-TDL, respectively, and 11 dogs were evaluated by preoperative and 7- to 10-days-postoperative computed tomography-lymphography (CTLG). No clinical symptoms with absent or minimal pleural effusion was defined as clinical improvement. Long-term remission (LTR) was defined as rapid resolution of pleural effusion and no recurrence for more than 1 year. Anesthesia time, operation time, the duration of hospitalization, and time until pleural effusion resolution were compared.

RESULTS

Clinical improvement was achieved in 91.7% of the cases (C-TDL, 4/5; EB-TDL, 7/7), excluding one case of intraoperative death. The LTR rate was significantly higher with EB-TDL (6/7 [85.7%]) than with C-TDL (1/5 [20%]). Anesthesia time, operation time, and time until pleural effusion resolution were significantly better with EB-TDL than with C-TDL. The rates of thoracic ducts visualization by postoperative CTLG were 100% (5/5) with C-TDL and 42.9% (3/7) with EB-TDL.

CONCLUSION

En bloc TDL was an effective treatment for canine idiopathic chylothorax in this patient population. It compared favorably to C-TDL, although missed branches at the time of surgery may explain the difference between C-TDL and EB-TDL in this small population of cases.

CLINICAL SIGNIFICANCE

En bloc TDL by VATS was an effective minimally invasive treatment for canine idiopathic chylothorax. Computed tomography-lymphography can be used for surgical planning and postoperative evaluation.

Spontaneous Resolution of Postoperative Chylothorax Following Surgery for Persistent Right Aortic Arch in Two Dogs

Two young dogs underwent surgical management of a persistent right aortic arch (PRAA) and developed chylothorax postoperatively. In both cases, the surgical procedure and anesthetic recovery were uncomplicated and routine. Following surgery, both patients appeared bright, alert, responsive, and previous signs of regurgitation had resolved. Dyspnea and tachypnea developed 1–2 days postoperatively in each patient, and chylous effusion was detected on thoracocentesis. For each case, a diagnosis of chylothorax was based on cytology and triglyceride concentrations of the aspirated pleural fluid. Similar protocols for monitoring were used in the treatment of each patient’s chylothorax. The duration and volume of chylous effusion production were closely monitored via routine thoracostomy tube aspiration. Both dogs rapidly progressed to recovery with no additional complications. With diligent monitoring, chylothorax secondary to surgical trauma can resolve in a rapid, uncomplicated manner.

Occlusion of the thoracic duct using ultrasonically activated shears in six dogs

OBJECTIVE

To assess the feasibility of sealing the thoracic duct (TD) in dogs using ultrasonically activated shears via thoracoscopy.

STUDY DESIGN

In vivo experimental study.

ANIMALS

Mature dogs (n = 6).

METHODS

Dogs were anesthetized without pulmonary exclusion and positioned in left lateral recumbency. Lymphangiography was performed to identify TD anatomy. Methylene blue was injected into the lymphatic catheter to identify the TD and its branches. Under thoracoscopic guidance (right dorsal 8-10th intercostal spaces), the TD was sealed with an ultrasonic device and lymphangiography was repeated. If the flow of contrast continued beyond the occlusion site, additional attempts to seal the duct were made. Dogs were euthanatized, the TD was excised and fixed in formalin for histopathology.

RESULTS

Thoracoscopic identification of the TD was possible in 5 dogs. Three dogs required conversion to a thoracoscopic-assisted approach and 3 dogs required resealing of the TD closer to the diaphragm. Thoracic duct occlusion (TDO) was ultimately achieved in all 6 dogs based on follow-up lymphangiography. TDO by tissue coagulation was confirmed by histopathology.

CONCLUSIONS

Thoracoscopic identification and occlusion of the TD using ultrasonically activated shears with bilateral lung ventilation is technically feasible in normal dogs and provides a less invasive alternative to open thoracotomy procedures.

Chylothorax Treated Via Thoracic Duct Ligation and Omentalization

Chylothorax is an uncommon, potentially life-threatening disease of dogs and cats. Medical records of 12 animals (five dogs and seven cats) undergoing surgical management of chylothorax from 2001 to 2005 were reviewed. All animals received thoracic duct ligation and thoracic omentalization. In some cases, a combination of subtotal pericardectomy and/or pleural stripping was also employed. All animals survived surgery, and none was lost to follow-up. Median survival time for cats was 209 days (range 2 to 1328 days), and for dogs it was 211 days (range 7 to 991 days). Although postoperative mortality was higher than in other recent studies, no complications could be directly attributed to thoracic omentalization. A controlled, prospective study is needed to compare outcomes of this management method to those of other methods.

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.

COMPARISON OF RADIOGRAPHIC AND COMPUTED TOMOGRAPHY LYMPHANGIOGRAPHY FOR IDENTIFICATION OF THE CANINE THORACIC DUCT

Standard radiographic lymphangiograms and computed tomography (CT) lymphangiograms were performed on 10 female dogs without intrathoracic disease. Positive contrast lymphagiography was performed by injection into a catheterized mesenteric lymphatic vessel, and lateral thoracic radiographs, ventrodorsal thoracic radiographs, and thoracic CTs were obtained. The number of visible ducts was recorded for each image at the midbody of the ninth thoracic vertebra (T9) through the first lumbar vertebra (L1). Data were combined for all dogs at each data acquisition point. Data were analyzed by comparing data from all three images independently, and then by combining data for the radiographs and comparing the study with the highest number of visible duct branches to the CT. Significant differences in numbers of branches were found at T11 and L1. This study suggests that CT may be able to quantify branches of the thoracic duct more accurately than standard radiographic lymphangiography.

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.

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.

Percutaneous arterial embolization and chemoembolization for treatment of benign and malignant tumors in three dogs and a goat

The term bland arterial embolization refers to catheter-directed delivery of particulate material for the purpose of embolizing selected arteries. This technique is used in humans to treat a number of conditions, including arteriovenous malformations, uterine fibroids, and epistaxis. The term chemoembolization refers to selective intra-arterial delivery of chemotherapeutic agents in conjunction with particulate material for the purpose of embolizing arteries supplying blood to a tumor. Compared with traditional modes of drug delivery, chemoembolization increases local concentration and dwell time of the chemotherapeutic agent, augments tumor ischemia, and minimizes systemic toxic effects. In humans, the technique has shown encouraging results in the treatment of a variety of nonresectable tumors. The present report describes techniques for percutaneous bland arterial embolization and chemoembolization in dogs and goats and results of these techniques in 3 dogs and a goat. Bland arterial embolization was performed in 2 dogs and the goat. The goals of treatment included pain palliation, reduction of tumor growth, and control of hemorrhage, and each animal was considered to have benefited from the procedure on the basis of the preprocedural goals. Chemoembolization was performed in 1 dog for treatment of a nonresectable hepatocellular carcinoma. Unfortunately, this dog did not live long enough to identify any response to treatment. Results for animals studied illustrate the feasibility of bland arterial embolization and chemoembolization in veterinary patients and suggest that embolization may provide an alternative method of treatment for animals with inoperable lesions.

Management of unremitting chylothorax by percutaneous embolization and blockage of retroperitoneal lymphatic vessels in 42 patients

PURPOSE

To demonstrate the applicability, technique, and efficacy of percutaneous transabdominal catheter embolization or needle disruption of retroperitoneal lymphatic vessels in the treatment of high-output or unremitting chylothorax.

MATERIALS AND METHODS

Forty-two patients (21 men, 21 women; mean age, 56 y; range, 19-80 y) who had chylothorax with various etiologies were referred from the thoracic surgery department for treatment as soon as chylothorax was documented. The thoracic duct was punctured and catheterized via a peritoneal cannula to facilitate embolization with use of microcoils, particles, or glue; if there were no lymph trunks that could be catheterized, attempts were made to disrupt lymph collaterals with use of needles.

RESULTS

The thoracic duct was catheterized in 29 patients and embolized in 26 patients. In patients with lymph trunks that could be catheterized, treatment resulted in cure within 7 days in 16 patients and partial response with cure within 3 weeks in six patients. In the patients with lymph trunks that could not be catheterized (n = 16), disruption with use of needles resulted in cure in five patients and partial response in two patients. Cure and partial response rates after thoracic duct embolization and needle disruption were 73.8%, with no morbidity. Surgical thoracic duct ligation was performed in seven patients. The nonprocedural mortality rate was 19%. Follow-up was 3 months or longer.

CONCLUSIONS

Effective percutaneous treatment of high-output or medically uncontrollable chylothorax was performed promptly and safely in more than 70% of referred cases. This procedure should be attempted, especially if patients are very ill, before riskier surgical thoracic duct ligation is considered.

Omentalization of the thorax for treatment of idiopathic chylothorax with constrictive pleuritis in a cat

A 6-year-old, spayed female Himalayan cat with idiopathic chylothorax, which failed to respond to medical management, was successfully treated by advancement of the omentum into the thorax. Exploratory thoracotomy revealed severe, constrictive pleuritis as a sequela to chylothorax. Because of the poor prognosis for recovery from chylothorax in cats with thoracic duct ligation alone, and the lack of success in performing thoracic duct ligation in this cat, the omentum was advanced into the thorax through a hole created in the diaphragm and sutured within the thoracic cavity. The cat recovered from surgery and is clinically normal 13 months postoperatively. Omental advancement may be an effective surgical management technique for this challenging disease in cats.

Use of omentum as a physiologic drain for treatment of chylothorax in a dog

OBJECTIVES

To describe a novel technique for the surgical treatment of idiopathic chylothorax in a dog.

ANIMALS

A 6-year-old, male Rhodesian Ridgeback, which presented with a history of reduced exercise tolerance and dyspnea.

METHODS

Idiopathic chylothorax was diagnosed. Intermittent pleural drainage failed to resolve the problem. During surgery, extensive pleural fibrosis made it impossible to identify the thoracic duct. A dorsal omental pedicle was advanced through an incision in the diaphragm and into the cranial thoracic cavity to act as a physiological drain.

RESULTS

The dog recovered well and has remained free from clinical signs of recurrence of the effusion (16 months at the time of writing).

CONCLUSIONS

The disease-free interval achieved in this dog indicates that this novel technique is worthy of further consideration in the management of idiopathic chylothorax.

Percutaneous transabdominal embolization of thoracic duct lacerations in animals

PURPOSE

To develop percutaneous techniques for lacerating the thoracic duct (TD) and to assess the efficacy of percutaneous TD embolization.

MATERIALS AND METHODS

The TD was catheterized by means of antegrade or antegrade-retrograde techniques after the lymphographically opacified cisterna chyli (CC) was punctured in five swine and one dog. The TD was lacerated by fluid overdistention (n = 1), perforated with stiff guide wires (n = 3) or a 5-F styletted catheter (n = 1), or macerated by rotational guide-wire trauma (n = 1). The TD was percutaneously embolized in five animals with steel (n = 2) and platinum (n = 3) coils. The CC containing a metal target was recatheterized 2-7 days after embolization.

RESULTS

All types of TD trauma led to mediastinal extravasation. The one chylothorax was induced by the 5-F styletted catheter. The TD of four animals was promptly thrombosed with coils. In the fifth animal, the TD failed to thrombose 3 days after embolization, probably because of the use of an undersized platinum are coil. There were no immediate or delayed complications. Necropsy in five animals was unremarkable. The sixth animal was alive and well at 4 months.

CONCLUSIONS

Percutaneous transcatheter TD trauma led to mediastinal extravasation in all six animals, but chylothorax occurred in only one animal. TD coil embolization led to duct thrombosis in four of five animals with no early or late complications. The technique has potential clinical applications for localization and selective embolization of TD leaks in debilitated patients.