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 associated with thrombosis of the cranial vena cava

This study reviewed confirmed cases of concurrent chylothorax and cranial vena caval (CrVC) thrombosis in dogs and cats, and determined predisposing factors for the development of chylothorax associated with CrVC thrombosis. The extent and location of the thrombus, the treatment regime, and the outcome are described. In all 4 cases, implantation of a jugular device was a predisposing factor to thrombosis of the CrVC, and there was extensive thrombosis of the CrVC extending from at least 1 jugular vein to just cranial to the heart. Chylothorax resolved in 3 of the 4 cases after medical and/or surgical intervention. The development of chylothorax concurrently with thrombosis of the CrVC in dogs and cats is likely dependent on the extent and location of the thrombus. Veterinary patients with indwelling jugular devices that develop acute respiratory signs should be assessed for chylothorax associated with thrombosis of the CrVC.     

Aortic to caudal vena cava ratio measurements using abdominal ultrasound are increased in dogs with confirmed systemic hypertension

Chronically sustained systemic hypertension in dogs can damage the kidneys, eye, brain, heart, and vessels. In human medicine, systemic hypertension has been implicated as the most common risk factor for aorta dilation, which can progress to an aneurysm. Abdominal ultrasound has been commonly used to monitor the size of the abdominal aorta in people with systemic hypertension. In this retrospective cross‐sectional abdominal ultrasound study, evaluation of the size of the abdominal aorta relative to the caudal vena cava was performed in 18 control dogs and 128 dogs with confirmed systemic hypertension. Preexisting conditions contributing to systemic hypertension in these dogs were renal disease, hyperadrenocorticism, diabetes mellitus, adrenal tumors, and previous administration of phenylpropanolamine or palladia. The abdominal aorta and caudal vena cava were assessed from longitudinal images cranial to the trifurcation with measurements made from outer border to outer border of the walls, being careful not to compress the caudal vena cava that would alter its size. Our hypothesis was the ratio of the diameter of the abdominal aorta to caudal vena cava would be higher in dogs with systemic hypertension compared to dogs with normal blood pressure. The mean abdominal aorta‐caudal vena cava ratio was 1.028 in control dogs with a normal blood pressure and 1.515 in dogs with systemic hypertension. In dogs with confirmed systemic hypertension, the abdominal aorta was dilated compared to the caudal vena cava in the caudal abdomen. An increase in the abdominal aorta‐caudal vena cava ratio in a dog should raise suspicion for the presence of systemic hypertension and prompt evaluation of blood pressure.     

Cranial vena cava aneurysm in a dog

A 1.5-year-old mixed breed dog was presented for evaluation of arrhythmia and a cranial mediastinal density was noted on thoracic radiographs. The density was determined to be a cranial vena cava aneurysm based on ultrasonographic and angiographic testing. No treatment was initiated and the dog remains asymptomatic for the cranial vena cava aneurysm at 6 years of age. Although rare, cranial vena cava aneurysm should be a differential diagnosis for dogs with cranial mediastinal abnormalities on thoracic radiographs.     

Effects of tetracycline hydrochloride on pleurae in dogs with induced pleural effusion

Pleural effusion was induced in 12 dogs by ligation of the cranial vena cava. Pleurodesis was attempted by injecting a solution of tetracycline hydrochloride into the pleural space of 8 dogs (4 dogs, 25 mg/kg of body weight; 4 dogs, 50 mg/kg) via bilateral thoracostomy tubes. In both groups, tetracycline was diluted in 40 ml of normal saline solution and 10 ml of 1% lidocaine before injection. Half of the solution (25 ml) was instilled in each hemithorax. Four control dogs were treated in the same manner with a solution of normal saline and lidocaine. Daily pleural fluid production was measured after the attempted pleurodesis. Thirty days after administration of the solution, each dog was euthanatized and necropsied. Surface area of pleural adhesions was measured. Tissues from regions of pleural adhesions and areas of parietal and visceral pleura not involved in adhesions were analyzed histologically. Formation of pleural fluid stopped in all but 1 control dog within 48 hours after injection of solution. This dog effused throughout the study. The resolution of effusion was not significantly (P less than 0.05) different between the tetracycline-treated dogs and the control group. Although diffuse pleural adhesions were not induced in any of the dogs, significantly (P less than 0.0027) more surface area of lung was adhered in dogs treated with the higher dose of tetracycline.     

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.     

RADIOGRAPHIC EVALUATION OF CANINE HEARTWORM DISEASE COEXISTING WITH RIGHT HEART FAILURE

Thoracic radiographs of 28 dogs with heartworm disease and right heart failure were evaluated subjectively and objectively. Radiographs of all dogs were abnormal. Abnormalities were consistent with those previously reported for heartworm disease but were more severe than those identified in another group of heartworm dogs that did not have right heart failure. The right ventricle and right caudal labor pulmonary artery were enlarged in every dog. The main pulmonary artery, right cranial lobar pulmonary artery, and caudal vena cava were enlarged in 24, 25, and 17 dogs, respectively. Radiographically apparent pathologic pulmonary conditions were present in 25 dogs. Pleural effusion was not identified.     

Chylothorax associated with dirofilariasis in a cat

A 4-year-old castrated domestic shorthair cat was referred for treatment of chylothorax. Thoracic duct lymphangiography revealed partial obstruction of the cranial vena cava, as evidenced by filling of mediastinal lymphatics with dye instead of all of the dye entering the vena cava. The thoracic duct was ligated via left 10th intercostal space thoracotomy. Immediate postligation lymphangiography revealed successful duct ligation. Results of a serum ELISA for adult heartworm antigen that was performed before surgery were positive. Drug treatment for the heartworm disease was not recommended, because the pleural effusion had ceased (as determined by radiographic examination 3.5 and 9 months after surgery) and the cat was doing well clinically. Sixteen months after surgery, the owner reported that the cat was doing well and did not have signs of respiratory problems.     

Evaluation of cholesterol and triglyceride concentrations in differentiating chylous and nonchylous pleural effusions in dogs and cats

Serum and pleural fluid cholesterol and triglyceride concentrations and cholesterol/triglyceride ratios were determined in 9 dogs and 9 cats with pleural effusion (8 nonchylous, 10 chylous). The pleural fluid triglyceride concentrations were significantly higher (P less than 0.05) and the pleural cholesterol/triglyceride ratios were significantly lower (P less than 0.05) in chylous effusions than in nonchylous effusions in all animals. There were no differences in serum cholesterol and triglyceride concentrations and serum cholesterol/triglyceride ratios for chylous and nonchylous effusions in either species. There also were no differences in pleural fluid cholesterol concentrations between the 2 groups in the dog or cat. It was concluded that determinations of cholesterol/triglyceride ratios may be an accurate method for helping distinguish chylous from nonchylous effusions in dogs and cats.     

Dysplasia of the tricuspid valve in the dog and cat.

Dysplasia of the tricuspid valve in 14 dogs and 13 cats was studied. The clinical, electrocardiographic, radiographic, hemodynamic, angiocardiographic, and pathologic findings were reviewed in each species. Alterations of the tricuspid valve complex included long, thick septal leaflets adhered to the septum; absent or short, stout fused chordae tendineae; hypertrophic fused papillary muscles; insertion of papillary muscles directly into the lateral leaflets; incomplete development of the valvular tissue; and enlargement of the right atrium and ventricle. Additional intracardiac anomalies included malformation of the mitral valve complex (5 dogs and 3 cats), ventricular septal defect (3 dogs and 3 cats), pulmonary stenosis (1 dog and 1 cat), aortic stenosis (1 dog and 1 cat), and persistent left cranial vena cava (1 dog).     

ULTRASONOGRAPHIC DIAGNOSIS: CRANIAL VENA CAVA THROMBOSIS IN A COW

A 5-year-old Hereford cow was donated to Oregon State University, College of Veterinary Medicine. Two weeks before presentation the cow was treated by a left-flank laparotomy to correct a uterine torsion that revealed an excessive amount of abdominal fluid and a full term dead fetus. Ultrasonographic evaluation of the right cranioventral thoracic cavity was performed owing to physical examination (muffled heart sounds, areas of silence) and thoracocentesis findings suggestive of pleuritis. Ultrasonography revealed hypoechoic pleural effusion and a mass of mixed echogenicity visible within the right atrial lumen extending into the cranial vena cava. A diagnosis of cranial vena cava thrombosis was demonstrated at necropsy. The clinical, ultrasonographic, and pathological features of this less common condition (cranial vena cava thrombosis) in cattle are discussed.     

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.     

Primary cranial mediastinal hemangiosarcoma in a young dog

Primary cranial mediastinal hemangiosarcomas are uncommon tumors. A 30-kg, 2-year-old, intact female German shepherd was presented for evaluation of cachexia and respiratory distress of a few days’ duration. Lateral radiographic projection of the thorax revealed significant pleural effusion. Computed tomography revealed a cranial mediastinal mass effect adjacent to the heart. On surgical exploration, a pedunculated mass attached to the esophagus, trachea, brachiocephalic trunk, left subclavian artery and cranial vena cava without attachment to the right atrium and auricular appendage was removed and debrided by use of blunt dissection and dry gauzes, respectively. Histopathology results described the cranial mediastinal mass as hemangiosarcoma. At 8 months and 5 days post-operatively, the patient died. Primary cranial mediastinal hemangiosarcomas, although a seemingly rare cause of thoracic pathology in young dogs, should be considered in the differential diagnosis for pleural effusion and soft tissue mass effect in the cranial mediastinum. This is the first case report in a dog to describe primary cranial mediastinal hemangiosarcoma.     

Cranial mediastinal carcinomas in nine dogs*

Nine dogs were diagnosed with cranial mediastinal carcinomas. Based on histological and immunohistochemical analysis, four dogs were diagnosed with ectopic follicular cell thyroid carcinomas, one dog with ectopic medullary cell thyroid carcinoma, two dogs with neuroendocrine carcinomas and two dogs with anaplastic carcinomas. Clinical signs and physical examination findings were associated with a space‐occupying mass, although one dog was diagnosed with functional hyperthyroidism. Surgical resection was attempted in eight dogs. The cranial mediastinal mass was invasive either into the heart or into the cranial vena cava in three dogs. Resection was complete in six dogs and unresectable in two dogs. All dogs survived surgery, but four dogs developed pulmonary thromboembolism and two dogs died of respiratory complications postoperatively. Adjunctive therapies included pre‐operative radiation therapy (n = 1) and postoperative chemotherapy (n = 3). Three dogs had metastasis at the time of diagnosis, but none developed metastasis following surgery. The overall median survival time was 243 days. Local invasion, pleural effusion and metastasis did not have a negative impact on survival time in this small case series.     

Hyponatremia and hyperkalemia associated with idiopathic or experimentally induced chylothorax in four dogs

Two dogs with idiopathic chylothorax and 2 dogs with experimentally induced (ie, ligation of the cranial vena cava) chylothorax were treated by intermittent thoracic drainage. Of these 4 dogs, 3 that did not have evidence of renal failure had normal or near-normal serum sodium and potassium concentrations before thoracic drainage began, and all 3 developed repeatedly marked hyponatremia and hyperkalemia during thoracic drainage. Another dog became weak and depressed, ostensibly because of hyperkalemia. Serum sodium and potassium concentrations in 1 dog with spontaneous chylothorax returned to normal after chylothorax resolved and thoracic drainage was stopped. The other 3 dogs died or were euthanatized, and the effect of stopping thoracic drainage could not be evaluated. In 3 dogs in which it was measured, normal-to-high plasma cortisol concentration was observed before and after adrenocorticotropin administration, and 2 dogs also had hyperaldosteronemia. Hyponatremia was hypothesized to be caused by sodium loss via thoracic drainage whereas hyperkalemia may have been multifactorial in origin, but probably was attributable, at least, in part to decreased renal potassium clearance.     

Central venous access to the cranial vena cava via the omobrachial vein in the dog

Background– The omobrachial vein is a superficial vein that crosses the brachial region of the dog. It terminates in the cranial vena cava, offering a novel site for central venous catheterization into the cranial thorax. Case Summary– The omobrachial vein served as a point of access to the cranial vena cava for treatment and monitoring of a critical canine patient in this report. The omobrachial vein was catheterized using the modified‐Seldinger technique due to contamination of or lack of availability of commonly used central venous catheter insertion sites. Conclusion– Access to the cranial vena cava via the omobrachial vein was easily achieved, and the catheter was maintained without complication for 10 days. Although the site was successfully used in the patient in this report, omobrachial vein anatomy is not consistent in all dogs.     

Cor triatriatum dexter of unusual morphology in a miniature schnauzer

A five-year-nine-month-old, male entire, miniature schnauzer presented for further investigation of pleural effusion. Echocardiography revealed a perforated membrane dividing the right atrium into two chambers: the true right atrium (a small, lower-pressure, cranioventral chamber communicating with the tricuspid valve and right ventricle) and the accessory right atrium (a larger, higher-pressure, caudodorsal chamber), consistent with a cor triatriatum dexter. This was confirmed using computed tomography angiography. Imaging studies revealed that both the cranial and caudal vena cava entered the higher-pressure accessory right atrium and the coronary sinus entered both the accessory and true right atrial chambers. This differed from the more usual canine cor triatriatum dexter presentation with the cranial vena cava entering the lower-pressure cranial chamber and the caudal vena cava entering the higher-pressure caudal chamber. Balloon membranostomy was successful in reducing the pressure gradient between the two right atrial chambers with subsequent resolution of the clinical signs. The patient continues to do well after three-years of follow-up.     

Cranial vena caval syndrome secondary to transvenous pacemaker implantation in two dogs

Superior vena caval syndrome is a rare, but reported complication of transvenous pacemaker implantation in humans. This syndrome can occur secondary to fibrotic and/or thrombotic obstruction of venous blood flow into the right atrium. The therapeutic approach depends on the suspicion of the presence of an active thrombus and may include antithrombotics, angioplasty and/or surgical venoplasty. We describe two dogs that developed severe pleural effusion secondary to stricture formation in the cranial vena cava 4 years after dual chamber transvenous pacemaker implantation. The stenosis was most likely due to fibrosis secondary to the transvenous pacemaker leads. Balloon angioplasty of the lesion resulted in resolution of the pleural effusion in both patients. Balloon angioplasty appears to be a viable therapeutic approach in dogs with cranial vena caval syndrome caused by focal stenotic lesions.     

Lung lobe torsion in association with a chronic diaphragmatic hernia and haemorrhagic pleural effusion in a cat

CLINICAL SUMMARY: This report describes torsion of the right cranial lung lobe in a cat with haemorrhagic pleural effusion and a chronic diaphragmatic hernia. Surgical treatment comprising lung lobectomy without de-rotation, and repair of the diaphragmatic defect, led to an uneventful recovery. PRACTICAL RELEVANCE: Lung lobe torsion is a rare condition in cats. While spontaneous lung lobe torsions may occur, a frequent association with underlying thoracic disease has been recognised in cats. However, neither haemorrhagic pleural effusion nor diaphragmatic hernia have been previously described in cats with lung lobe torsions, although they have been documented in dogs and humans. In a cat with suspected lung lobe torsion, a thorough search for an underlying disease should be undertaken.     

Lipoprotein electrophoresis differentiation of chylous and nonchylous pleural effusions in dogs and cats and its correlation with pleural effusion triglyceride concentration

Pleural effusions from 23 dogs and 25 cats hospitalized between November 1986 and April 1987 at the Veterinary Hospital of the University of Pennsylvania (VHUP) were classified as chylous (chylomicrons present) or nonchylous (chylomicrons absent) by the presence or absence, respectively, of a chylomicron band on lipoprotein electrophoresis gels of the effusions. Triglyceride concentrations, cholesterol concentrations, and cholesterol/triglyceride (C/T) ratios were compared between the chylous and nonchylous groups in each species. Cholesterol concentrations were not significantly different between chylous and nonchylous effusions in both dogs and cats. Cholesterol/triglyceride ratios of less than 1 were present in all dogs and cats with chylous effusions; however, 12% of dogs with nonchylous effusions and 50% of cats with nonchylous effusions also had a C/T ratio less than 1. Triglyceride concentrations accurately classified all effusions as chylous or nonchylous in both dogs and cats. Pleural effusions with triglyceride concentrations greater than l00 mg/dl were chylous in all cases, whereas, effusions with triglyceride concentrations less than l00 mg/dl were nonchylous in all cases.