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.     

Lymphoscintigraphy in healthy dogs and dogs with experimentally created thoracic duct abnormalities.

Lymphoscintigraphic evaluation of the thoracic duct (TD) was performed in 10 healthy and 12 dogs with experimentally created TD abnormalities (6 dogs with TD lacerations and 6 dogs with cranial vena ligations). Complete imaging took 4 hours and caused no adverse effects or complications. Lymphoscintigraphy of healthy dogs failed to image the TD; however, background activity in the abdomen and thorax, and radioactivity in the kidneys, bladder, liver, and heart were noticed. Lacerations and transections of the TD were experimentally created in 6 dogs to ascertain whether TD rupture could be detected with lymphoscintigraphy. Lymphoscintigraphy was performed within 48 hours of creating the TD defect. There was no significant difference in the scintigraphic pattern of healthy dogs and those with experimentally created TD defects. Ligation of the cranial vena cava was performed in 6 dogs; 3 dogs developed chylothorax. In those 3 dogs, diffuse radioactivity was imaged in the thorax and was compatible with thoracic lymphangiectasia. In one of these dogs, linear activity consistent with the TD and localized regions of radioactivity cranial to the heart (compatible with the mediastinal lymph nodes) were noticed. Lymphoscintigraphic findings in these dogs correlated with lymphangiographic findings.     

Mesenteric lymphography and ligation of the thoracic duct in a cat with chylothorax

Mesenteric lymphography was used to identify and ligate the thoracic duct in a 1-year-old Himalayan cat with chylothorax. Lymphography revealed the thoracic duct to be intact; however, multiple dilated lymphatics, indicative of lymphangiectasia were evident in the cranial portion of the thorax. Hemostatic clips were used to ligate the thoracic duct. The effusion stopped, and 9 months after surgery, effusion has not recurred.     

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.     

Results of thoracic duct ligation in dogs with chylothorax

Thoracic duct lymphangiography and ligation were done on 15 dogs with idiopathic chylothorax. Lymphangiography revealed thoracic lymphangiectasia in all dogs; none had a thoracic duct rupture. Lymphangiography immediately after ligation demonstrated missed branches of the thoracic duct in 4 of the 15 dogs. Eleven of the 15 dogs are alive and doing well. Eight of the 11 had no radiographic or clinical signs of pleural effusion (mean follow-up, 31.5 months; range, 4 to 75 months). The other 3 living dogs had persistent effusion; 2 were successfully managed with a pleuroperitoneal shunt (follow-up, 15 months) or pleurodesis (follow-up, 5 months), respectively, and 1 was not treated because the effusion was mild and the dog did not have clinical signs of disease (follow-up, 14 months). Four of the 15 dogs died or were euthanatized because of persistent effusion (mean follow-up, 11.5 months; range, 3 to 24 months). Considering the lack of treatment alternatives for dogs with idiopathic chylothorax, these results support thoracic duct ligation as a treatment method for dogs.     

Caudal mediastinal thyroglossal duct cyst in a cat

An eight-year-old domestic shorthair cat was evaluated because of dyspnoea secondary to pleural effusion. Ultrasound examination identified a large anechoic cyst-like structure in the caudal thorax. A median sternotomy was performed, and the cystic mass was removed. Microscopically, the excised tissue was identified as a multilocular thyroglossal duct cyst with ectopic thyroid tissue. To the authors' knowledge, this is the first report of a mediastinal thyroglossal duct cyst in a cat. Despite the rarity of this lesion, it should be considered when a cystic thoracic structure is identified on thoracic ultrasound. Surgical excision of the cyst resulted in complete resolution of the pleural effusion and clinical signs.     

Thoracoscopic Thoracic Duct Ligation and Thoracoscopic Pericardectomy for Treatment of Chylothorax in Dogs

Objective— To report the use of thoracoscopic thoracic duct ligation (TDL) and pericardectomy for treatment of chylothorax.
Study Design— Case series.
Animals— Dogs with chylothorax (n=12).
Methods— Dogs with secondary or idiopathic chylothorax had thoracoscopy performed in sternal recumbency through 3 portals in the caudal right hemithorax for TDL and were then repositioned in dorsal recumbency for pericardectomy. Portals were placed in the 5th and 7th intercostal spaces of the right hemithorax with 1 transdiaphragmatic portal in the right paraxiphoid position. Follow-up was performed by recheck examination or telephone interview to determine outcome.
Results— Seven dogs (58%) had idiopathic chylothorax; 6 dogs (85.7%) had complete resolution of their effusion, whereas only 2 of the 5 nonidiopathic dogs (40%) had complete resolution.
Conclusions— Thoracoscopy is minimally invasive, provides excellent observation, and allows for ligation of the thoracic duct in the caudal thorax. Patients with idiopathic chylothorax may have a better prognosis after TDL and pericardectomy than dogs with nonidiopathic chylothorax.
Clinical Relevance— Thoracoscopy for ligation of the thoracic duct and pericardectomy is an acceptable surgical technique for treatment of chylothorax.     

Thoracoscopic visualization and ligation of the thoracic duct in dogs

OBJECTIVE: To develop a technique for thoracoscopic visualization and ligation of the thoracic duct in dogs. STUDY DESIGN: In vivo experimental study. ANIMALS: Five mature, healthy dogs. METHODS: Dogs were normal based on physical examination, negative occult heartworm test, normal complete blood count and biochemical profile, and normal thoracic radiographs. The dogs were anesthetized, and a ventral midline laparotomy was performed for catheterization of a mesenteric lymphatic. Lymphangiography was performed to determine thoracic duct anatomy. Thoracoscopy was performed in the caudal, right hemithorax after single lung intubation or bronchial blockade. At least two 10-mm clips were placed across the thoracic duct in each dog. Lymphangiography was repeated to assess duct ligation. If complete duct occlusion was not achieved, thoracoscopy was repeated for additional clip placement. After surgery the dogs were euthanatized, and necropsies were performed. RESULTS: Lymphangiography showed that multiple branches of the thoracic duct were present in every dog; bilateral thoracic duct branches were most common. Thoracoscopic identification and ligation of the thoracic duct was successful in all five dogs. Two dogs required a second thoracoscopic procedure to completely occlude flow of contrast through the thoracic duct. Surgery time for thoracoscopy averaged 59 plus minus 9.6 minutes. Retroperitoneal contrast accumulation after thoracic duct ligation occurred in two dogs. One dog required bilateral pulmonary ventilation. CONCLUSION: Thoracoscopy can be used to visualize the thoracic duct for ligation in normal dogs. CLINICAL RELEVANCE: Thoracoscopic ligation of the thoracic duct may be a therapeutic option for management of chylothorax in dogs.     

ULTRASONOGRAPHIC FEATURES OF INTESTINAL ENTRAPMENT IN DOGS

The clinical and ultrasonographic features of postoperative intestinal entrapment were assessed in five dogs. Four had vomiting and lethargy, and one had peracute collapse and hematochezia. Ultrasonographic findings in four of five dogs were similar, being characterized by focally hyperechoic mesentery and abdominal effusion, surrounding a single loop of amotile and dilated intestine. In some dogs, the affected intestinal loop had a thickened or corrugated wall, or alteration of wall layering. In one dog, the site of entrapment could be directly visualized. In the most severely affected dog, a large volume of echogenic peritoneal effusion was present, as well as fluid dilation of multiple intestinal loops. The ultrasonographic appearance of intestinal entrapment is similar to that of intestinal perforation or infarction by other causes.     

Idiopathic hemorrhagic pericardial effusion in eight dogs

Idiopathic hemorrhagic pericardial effusion was diagnosed in 8 dogs. The patients were typically males of large or giant breeds and a wide age range was represented. In all dogs clinical features of acute or chronic cardiac tamponade and right-sided heart failure were present. The pericardial effusion in each case was identified by thoracic radiography, electrocardiography, and echocardiography. Cytologic examination of the fluid did not allow differentiation from hemorrhagic effusions caused by neoplasia. Bacterial and fungal cultures were negative in 5 dogs. In 6 cases, a presumptive diagnosis was based on the absence of cardiac masses on 2-dimensional echocardiography, contrast pericardiography, or both. The condition was managed successfully by partial pericardiectomy in 5 cases. The definitive diagnosis in each case was established by gross cardiac examination at surgery or necropsy and by histologic examination of tissues. Blood vessels and lymphatics of the parietal and visceral pericardia appeared to be the primary targets of the disease process.     

CT is helpful for the detection and presurgical planning of lung perforation in dogs with spontaneous pneumothorax induced by grass awn migration: 22 cases

Spontaneous pneumothorax induced by grass awns accounts for 5% of spontaneous pneumothorax and 22.5% of thoracic grass awn cases. Previous studies report limited interest of CT for spontaneous pneumothorax. Aims of this retrospective case series were to describe CT features of this condition and determine if CT features can efficiently localize the perforation site. Dogs that had a spontaneous pneumothorax, CT examination, thoracic surgery, and confirmed lung perforation due to a grass awn were included. Computed tomography studies were reviewed and compared to the surgical findings.  In 19 of 22 (86.4%) dogs, the pneumothorax or its recurrence were ipsilateral to the perforation site. The perforation site was identified in 21 of 22 (95.5%) dogs and involved the caudal lobes in 20 of 22 (90.9%) cases. The lateralization and the involved lung lobe corresponded to surgical findings in 21 of 22(95.5%) dogs. The perforation site was characterized as a soft tissue attenuating focus lying against an extensive pleural thickening in 21 of 22(95.5%) dogs. An adjacent defect in the visceral pleura was seen in 13 of 22(59.1%) dogs. A grass awn was seen in 11 of 22(50%) dogs.  The pneumothorax distribution and grass awn position consistently indicated the perforation side in this sample of dogs. The comparison with surgical findings suggests CT might be helpful for future presurgical planning of this etiology for pneumothorax.     

Spontaneous cholangiofibrosis adjacent to a dilated common bile duct with intestinal metaplasia in a Royal College of Surgeons rat

A 130-week-old male Royal College of Surgeons rat kept as a non-treated animal in a long-term animal study presented with a mass in the hepatic portal region that adhered to a dilated common bile duct and the duodenum. Histopathologically, the solitary mass showed expansive growth with no apparent compression and continued to dilate the common bile duct, which had a hyperplastic epithelium with intestinal metaplasia. The mass mainly consisted of small to large dilated and/or tortuous ducts with abundant dense connective tissue and many inflammatory cells. The single-layer lining epithelium of the duct changed from cuboidal to columnar. Immunohistochemically, the lining cells were positive for cytokeratin 7, cytokeratin 19, and OV-6, which are bile duct markers. Based on the pathological characteristics, the rat was diagnosed as spontaneous cholangiofibrosis adjacent to a dilated common bile duct with intestinal metaplasia.     

Presumptive migrating gall bladder mucocoele in two dogs with gall bladder rupture

A 10‐year‐old neutered female soft‐coated wheaten terrier and a 10‐year‐old, entire female Pomeranian were presented for vomiting and anorexia. Using ultrasound, an oval structure with a stellate, kiwifruit‐like appearance typical of a gall bladder mucocoele was observed in the caudal abdomen of the soft‐coated wheaten terrier and adjacent to the liver in the Pomeranian. There was also a moderate volume of abdominal effusion in both dogs. Cytology of the peritoneal fluid indicated a sterile exudative process but varied between the two dogs, with an absence of bile pigment in the soft‐coated wheaten terrier and marked bile peritonitis in the Pomeranian. An entire free‐floating ectopic mucocoele was confirmed via exploratory laparotomy with concomitant gall bladder rupture and common bile duct obstruction. Both dogs recovered completely after surgery. This is the first report of cases of gall bladder rupture with entire free‐floating gall bladder mucocoeles in dogs.     

Thoracic wall and pulmonary trauma in dogs sustaining fractures as a result of motor vehicle accidents

The records of 267 dogs seen at the University of Minnesota Veterinary Teaching Hospital for fractures resulting from motor vehicle accidents were examined to determine the prevalence and types of thoracic wall and pulmonary trauma associated with such cases. Results were analyzed for type and prevalence of thoracic wall and pulmonary injury, and for the prevalence of such injury in dogs with and without extrathoracic injury, in dogs with fractures of single vs multiple bones, in dogs with single fractures of specific bones, in dogs with fractures in the cranial vs the caudal one half of the body, and in dogs with fractures ipsilateral vs contralateral to thoracic injury. The overall prevalence of thoracic wall and pulmonary trauma was 38.9%; pulmonary contusions, pneumothorax, and fractured ribs were the most common injuries. More than 1 type of thoracic wall or pulmonary injury was diagnosed in 57.7% of the cases. Of the dogs with thoracic injury, 24% also had extrathoracic injuries; 16.5% of dogs without thoracic injury had extrathoracic injuries, not including fractures. Of the dogs with fractures of 1 bone, 36.3% had thoracic injuries. Of the dogs with fractures of more than 1 bone, 42.3% had thoracic injuries. The prevalence of thoracic wall and pulmonary trauma was significantly associated with the site of the fracture (cranial vs caudal and ipsilateral vs contralateral); significant association with the specific bone fractured was also seen for some fractures.     

Cyanoacrylate tissue adhesive for treatment of refractory corneal ulceration

Isobutyl cyanoacrylate tissue adhesive (BCTA) was used in the treatment of refractory superficial corneal ulcers in 17 dogs, one cat, and one rabbit, present 2 weeks to 7 months (mean 6.8 weeks +/- 6.1) prior to referral. Little to no sedation was required in the majority of cases, with only topical anesthetic applied prior to debridement and BCTA application. The presence of the tissue adhesive caused mild discomfort for several days after application, as reported by the owners. The ulcers healed, and the tissue adhesive sloughed in approximately 3 weeks (+/- 1 week). Mild neovascularization of the cornea resolved with topical corticosteroids. The use of BCTA offers a simple, safe and noninvasive treatment for refractory corneal ulcers.     

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.     

COMPUTED TOMOGRAPHIC FEATURES OF LUNG LOBE TORSION

The imaging features of lung lobe torsion in 10 dogs (nine complete, one partial torsion) acquired with a helical single‐slice computed tomography (CT) unit are described. Attenuation values of normal, rotated, and adjacent collapsed lung lobes before and after intravenous contrast medium administration were compared. Affected lung lobes were: left cranial (5), right middle (3), right cranial (1), and left caudal (1). CT findings in nine dogs with complete lung lobe torsion included pleural effusion and an abruptly ending bronchus. In eight of these dogs, enlargement, consolidation, emphysema of the affected lung lobe, and mediastinal shift to the contralateral side were present. Rotated lung lobes did not enhance, whereas adjacent collapsed and aerated lung lobes did (P<0.05). Apnea induced with hyperventilation or breath‐hold is essential to reduce motion artefacts and obtain a diagnostic study.     

Variations in the canine thoracic duct system and the effects of surgical occlusion demonstrated by rapid aqueous lymphography, using an intestinal lymphatic trunk

An alternative method for lymphography was developed in an attempt to improve the outlining of the thoracic duct system. Lymphograms obtained on 20 normal dogs demonstrated a large extent of anatomic variation. A complete obstruction of the thoracic duct was created in six dogs through transpleural resection and ligation. The lymphatic system responded by opening lymphaticovenous anastomoses proximal to the site of obstruction.