The diagnosis and treatment of Canine Chylothorse

Definition and signalment
Most cases of chylothorax in dogs are idiopathic, as well as this case. Chylothorax can also occur secondary to TD trauma, right-sided heart disease, heartworm disease, lung lobe torsion, neoplasia, thromboembolism, congenital abnormalities, diaphragmatic hernia, and lymphangiectasia. Several breeds are predisposed to idiopathic chylothorax, including the Afghan hound, mastiff, Shetland sheepdog, and Shiba Inu. While no consistent age or sex predisposition has been found, Shiba Inus tend to be affected at a younger age. In one study of 19 male and eight female dogs, the reported mean age was 3.8 years. In a second study median age was 4.3 years, and in a third study mean age was 4.6 years (range 3-7 years). No sex predisposition has been noted.
Monitoring and Complications
Monitoring varies depending on the underlying cause. Repeat thoracic imaging is often performed to monitor the recurrence of pleural effusion. Complications after treatment of chylothorax include recurrent chylothorax, non-chylothorax effusion, chylothorax, or restrictive pleurisy. Pleural effusion recurrence is usually after surgical management, and the time to resolve pleural effusion is variable. In one report, the resolution of pleural effusion ranged from 1 to 50 days after surgery. In another study, three out of 35 dogs that survived the perioperative period relapsed at 12, 12, and 19 months. The new fluid may be chylous or non-chylous in nature. Chylous fluid often occurs due to the absence of TD branches or the presence of new branches. The above surgical methods can be used to treat recurrent or unresolved chylous fluid. Most non-chylous cases are thought to be secondary to inflammatory pleurisy or abnormal lymph. In one study, 33% of diseased dogs developed non-chylous fluid. Several approaches have been described for the management of chronic, non-chylous pleural effusion as follows:
1) Subcutaneous pleural opening: Traditionally, the stormy pleural tube is left in place to monitor immediate postoperative pleural effusion. However, a permanent subcutaneous pleural opening can be placed for long-term, intermittent pleural drainage. These ports are well tolerated, and the fluid can be easily drained using a special Huber dot needle, allowing repeated inspiration without damaging the port.
2) Active pleural shunt: The shunt device consists of an inflow tube and is placed in the chest; A pump cavity is placed in the subcutaneous tissue above a rib; There is also an outflow tube inserted into the abdomen. By manually compressing the pump chamber, 1mL of pleural fluid is directed from the chest to the abdomen. Most users can learn how to determine when and how to use the device effectively. For some animals, pump compression may be required multiple times per day. Most dogs tolerate this diversion well. Denver ShuntTM has been used in most patients. Although effective, short – and long-term complications (e.g., pump blockage, infection) have been reported.
3) Corticosteroids: In one study, postoperative non-chylous effusion was treated with anti-inflammatory doses of prednisone for 4-6 weeks. Three out of five (60%) dogs had fluid resolved.
Restrictive pleuritis
The development of restrictive pleurisy has often been reported but is not well understood. Inflammation of chylous, repeated thoracotomy and chronic disease may be precursors. Restrictive pleurisy is a thick fibrous membrane or granulation tissue that forms within the adjacent or visceral pleura. Inflammatory infiltration and adhesion formation are also common. This capsule limits the expansion of the lungs and can cause breathing disturbances even with proper pleural drainage. Fibrotic substances can also cause the lung parenchyma to contract. The presence of restrictive pleura may be an indicator of poor prognosis. However, there are limited reports on the incidence and treatment of restrictive canine pleurisy. The severity of pleurisy and the degree of associated pulmonary insufficiency may be more important than the mere presence or absence of restrictive pleurisy. Timely treatment of chylothorax is the best way to prevent restrictive pleurisy. Surgical stripping of fibrous membranes has had a limited success rate, and serious complications (e.g., bleeding, parenchymal injury, pneumothorax) have been reported. These complications are associated with chronic close adhesion of the pleura to the lung. In early or mild cases, it is possible to successfully remove the skin.
Prognosis
The prognosis varies depending on the underlying cause. TDL has been reported to have a 53-60% success rate in dogs. One study reported clinical improvement in 91.7% of cases when routine clipping and overall ligation were performed during video-assisted thoracoscopic surgery. The second study reported the resolution of pleural effusion in 35/37 dogs that underwent video-assisted thoracoscopic TDL and pericardiectomy. The third study described clinical improvements in 11 out of 12 dogs. The success rate for CCA and TDL combined therapy dogs is 83-88%. However, despite appropriate treatment, some patients develop chronic chylothorax and constrictive pleurisy.