Case study: Surgical intervention for Chylothorax

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Boris is a four-year-old Dogue de Bordeaux with a history of weight loss, hyporexia, lethargy and increased respiratory rate. This was noticed after the owners returned home after being away for several weeks. The primary care veterinarian found that he had an increased respiratory rate and effort and dull lung sounds. He was referred to Brisbane Veterinary Specialist Centre (BVSC) and was in respiratory distress on admission. 

Boris was dull with a marked increased respiratory effort. There were no bronchovesicular sounds present bilaterally on auscultation and he was clinically dehydrated. A thoracic ultrasound revealed a large volume pleural effusion so thoracocentesis was performed with a total of 7.3 litres of chylous fluid removed. This relieved his respiratory distress and he was given intravenous fluid resuscitation. Once he was stable, thoracic radiography was performed with three-view chest projections.  There was scant pleural effusion and no other pathology was seen.

Boris continued to do well after thoracocentesis. The results of the fluid analysis were consistent with a chylous effusion with triglycerides at 9.8 mmol/l and with a lower cholesterol level compared to Boris’ serum. 

chylothorax
Top image shows the sagittal reconstruction of the abdominal lymph vessels to the thoracic inlet. There are 2 -3 small branches in the area between T10-T13 (dorsal reconstruction, left bottom image), and transverse reconstruction on the bottom other two images (pink arrowheads).

Boris had an echocardiogram and there was no underlying cardiac disease.  There was also no evidence of mediastinal lymphoma. Based on these results, the diagnosis was idiopathic chylothorax.

To further clarify this diagnosis, Boris had a popliteal lymphagiography where contrast material was injected under ultrasound guidance into his popliteal lymph node to produce a CT lymphagiogram of the thoracic duct. This allowed accurate identification of the branching of the thoracic duct in the caudal thoracic region, as well as to evaluate for any leaks in the thoracic duct. By accurately identifying the number of branches to be ligated, the success of surgery is improved as some branches may not be accurately visualised at time of surgery especially if the aorta overlies some of the branches.  Based on this study, surgical intervention was planned.

There are various surgery techniques reported for the management of idiopathic chylothorax as this is a complex and variable disease. A recent review by Reeves et al 2019 found the overall reoperation rate across multiple studies was 23%.

In Boris’s case, he had thoracic duct ligation and subtotal pericardectomy. To help improve visualisation of the thoracic duct during surgery, Boris had dilute methylene blue injected into the ileocaecal lymph node. The abdomen was approached via a right paracostal incision at the same time as a right tenth intercostal thoracotomy. The thoracic duct and all the aberent branches, now clearly delineated by methylene blue dye, were ligated with ligating clips. A right fifth intercostal thoracotomy was then performed for a subtotal pericardectomy which was completed with the aid of a bipolar vessel sealing device (Ligasure®). A thoracostomy tube was placed to achieve negative pressure after routine thoracotomy closure and to monitor for pleural fluid production. 

chylothorax
Above: the thoracic duct highlighted with the dye (blue arrow). The pleura was thickened and has been incised to reveal the duct.

Boris recovered uneventfully from his surgery and the chylous pleural fluid resolved immediately after surgery. His thoracostomy tube was left in place for approximately 48 hours and only serosanguinous fluid was removed as is typical following intrathoracic surgery.

On his first recheck, two weeks after surgery by Dr Marvin Kung, Boris was eating well, and his energy levels were back to a 100%. He had also gained weight. He continued to do well with the subsequent rechecks three months apart with no evidence of recurrent effusion. 

Approximately nine months later, Boris presented for marked polyuria and polydipsia, a decreased appetite, weakness, lethargy and weight loss. There were no respiratory signs and no abdominal distension. There was hypercalcaemia along with enlarged peripheral lymph nodes. Unfortunately, cytology was consistent with lymphosarcoma. The owner declined further procedures and treatment. This late development of lymphosarcoma after resolution of chylothorax is unlikely to represent emergence of a pre-existing or causative disease and may indeed be a tragic independent event. Boris did enjoy a period of very good quality of life following resolution of his life-threatening chylothorax and there are treatment options for lymphosarcoma which were discussed with the owners.


Dr Marvin Kung BVSc MANZCVS Dip ACVS-SA 

chylothorax


Dr Marvin Kung, originally from Malaysia, is a key board-certified surgeon at Brisbane Veterinary Specialist Centre. He is highly trained and adept in all areas of small animal surgery but has a special interest in surgical oncology and spinal surgery. Dr Kung has performed many delicate spinal surgeries and with his meticulous approach to surgery, and specialised individual patient care, has established his high reputation. Dr Kung is a member of the Australian and New Zealand College of Veterinary Scientists in Small Animal Surgery, a Diplomate of the American College of Veterinary Surgeons and a registered specialist with the Queensland Veterinary Surgeons Board. His special interests in neurosurgery (especially surgery for spinal disease) and surgical oncology are supported by the facilities, equipment and staff at BVSC. With Dr Kung’s dedication and talent in the spinal surgery field, the team at BVSC continue to invest resources and people to support ongoing success and advancement in this important and often very difficult area.

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