Chylothorse can occur in dogs and cats of all ages, Afghan hounds, and Shiba inuses with a tendency to suffer this disease. Reported that respiratory distress is one of the most common sign we meet , more subtle symptoms such as weakness, anorexia, weight loss and exercise intolerance are common. In some cases, coughing is the only symptom. The causes of chylothorax need to be investigated in the following aspects: CBC, blood biochemistry, urinalysis, cytology of pleural effusion, thorax X-ray to evaluate mediastinal mass or chest mass, heartworm detection, echocardiography, etc. .The most common cause of disease is rupture of the thoracic duct. Other causes include: Trauma, tumor, heartworm, and long-term placement of an indwelling needle in the jugular vein may also cause chylothorax. In cats, diaphragmatic hernia and cardiomyopathy may also cause chylothorax, and lobular torsion has also been reported in dogs. In general, fluid leakage from a ruptured thoracic duct into the pleural cavity occurs at a rate of approximately per kilogram per hour (about 960ml per day for a 20kg dog). This means that within 2-3 days of the trauma, the dog may already be experiencing shortness of breath and difficulty breathing. Medical treatment includes low-fat prescription food, rutin, some doctors also suggest octreotide, etc., regular review, if the pleural effusion occurs again need to be punctured again. Indicators to evaluate the effectiveness of medical therapy, such as decreased frequency of puncture. Surgical treatment included thoracic duct ligation and partial pericardiectomy. Due to the high equipment and technical requirements of surgical treatment, surgical treatment may be considered when medical treatment is not effective.
Key words: Canine,Chylothorse ,diagnosis
Name： CHAI CHAI
Breed： Shiba Inu
Sex： Female (castrated)
Age：3 years old
Body weight：6.9 kg
History： Complete vaccination and deworming, coughing when she was young.
The owner feeds her at home， with no contact with other animals or humans. Two weeks ago, the dog was found to start to appear short of breath, losing appetite, and weak. The owner found it in a low spirit than usual. So decided to take her to the hospital. Vaccinate history is completed, and deworming is this year.
Body weight 6.9 kg， temperature 39.6℃， respiratory rate was 120/min、, heart rate：120 beats/min. Heavy and unclear murmurs in breathing. Mouth mucosa was pink， capillary refill time（CRT）=2s、body condition score（BCS）was 4/9, which can touch the ribs in palpation. The patient was presented with a highly depressing situation. Dry coat and nose. Abdominal palpation was found nothing obvious abnormal. There were mild dental calculus and gingivitis in an oral examination. The surface hair of the skin was the day. The dehydration was evaluated at 5%. In palpation, the rate of the femoral artery was equal to the heart rate.
Complete Blood Count (CBC) examination
Interpretation:There was a mild increased in the OTHER%. Red blood cell count and HCT indicate a possibility of dehydration that may have a low liquid volume,combined with the performance of the patient,but they were still in the reference range.
Idexx Catalyst biochemistry CHEM17
Interpretation:There was a obvious increase in ALT,CREA which is a cue for the cell injury and dehydration.No obvious abnormalities in other biochemical indicators.
The result of the CRP testing
Interpretation:The result of CRP was normal.
The PCR result of infectious examination
The radiography of X-ray examination of thoracic
Picture 1.Markedly radiopaque markings were found in the thorax of patient.（VD radiograph）
Picture 2. Markedly radiopaque markings were also found in the thorax of patient. -Right lateral radiograph
The diagnosis methods for Canine chylothorax usually used in veterinary clinics consist of the physical examination findings or history, laboratory examination such as complete blood count, serum biochemistries profile, fluid analysis(pleural), heartworm antigen test on serum, acid-base analysis, cytology, biopsy, histopathology, radiography, ultrasonography and even using advanced imaging.
Some clinical signs are common, such as tachypnea, coughing, dyspnea, and exercise intolerance. On the other hand, nonspecific signs like appetite decrease and weight loss have also been reported. More abnormalities might be present depending on the underlying cause. In this case, we take complete blood counts, common in anemia, leukopenia, lymphopenia, and neutrophilia. But we only find a possibility of neutrophilia. In serum biochemistry, the common result of hyperkalemia, hyponatremia, and hypoproteinemia were not found. Then the impact of the heartworm antigen test on serum was negative. Luckily, the performance of not visualized cardiac silhouette and the pleural effusion in the X-ray was typical. According to the result of the radiography, history, and the breed of Shiba Inu, we had highly suspected that the dog was suffering from chylothorax. Since there is a lack of examination, in this case, the other cause may not be excluded.
（1）Thoracentesis: Intermittent thoracentesis may be performed as often as necessary to relieve respiratory signs. Because many dogs have an incomplete mediastinum, bilateral drainage may not always be necessary. Repeat thoracotomy with an increased risk of introducing infection and/or developing other complications. If frequent repetition of thoracotomy is required, other treatment options should be considered. Complications (e.g., restrictive pleurisy, pneumothorax) may occur if a thoracotomy does not relieve respiratory distress.
（2）Diet modification: In the past, a low-fat diet combined with medium-chain triglyceride (MCT) oil has been recommended. It is thought that by reducing dietary fat, the chylous volume will be reduced. It has also been suggested that it bypasses TD and is absorbed directly into the venous circulation. Both theories have been proven wrong in dogs. However, feeding a low-fat diet may still reduce the lipid content of chylous, which may make it more susceptible to pleural reabsorption. Because deficiencies in protein and fat-soluble vitamins may occur in patients with chylothorax, it is important to develop a balanced, appropriate nutritional plan to address these deficiencies
（3）Nutrition: Rutin, a benzopyranone, is commonly used as an admissible nutritional supplement in dogs and cats with idiopathic chylothorax or lymphedema. Although the exact mechanism of action is unknown, it may stimulate macrophage activity and promote the breakdown of proteins in lymph fluid, thereby improving reabsorption. Although objective clinical data on its efficacy are lacking, there are no contraindications for its use as adjunctive therapy. It appears to be well tolerated. Rutin is administered at 50 mg/kg PO q for 8 hours.
（4）Supportive therapy： Therapy with supplemental oxygen and intravenous fluids to correct dehydration and electrolyte imbalances once a day.
Medication: Currently, there is no clinical data to support the use of diuretics or corticosteroids for the treatment of idiopathic chylothorax, and their use is not recommended. Octreotide is a somatostatin analog that has been used in a small number of dogs with mixed results. It is thought to reduce the flow of chylous through TD and thus reduce the amount of pleural effusion. However, further research is needed before this treatment can be recommended.
The diagnosis and treatment of Canine Chylothorse
The symptoms of breath has been relief after 7 days of therapy
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.
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.
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.