Page 177 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery

This procedure is technically demanding and should Omentalization, pericardectomy and cisterna chyli abla-
only be attempted by veterinary surgeons with thoracic tion: Placing omentum into the thoracic cavity, removing
VetBooks.ir equipment including Doppler or direct arterial blood pres- that were initially used when thoracic duct ligation failed to
the pericardium and cisterna chyli ablation are procedures
surgical experience. Specialized equipment (monitoring
resolve chylothorax. These procedures are now being used
sure measurement, pulse oximeter or blood gas machine,
end-tidal CO 2 monitor, chest retractors) is required.
combined with thoracic duct ligation. The omentum is
The patient is fasted for 12 hours before surgery. as ‘primary’ surgical treatments for chylothorax, generally
i
Anaesthesia is induced and the animal prepared for asep- thought either to act as a physiolog cal drain, when placed
tic surgery. Strategies for minimizing postoperative pain in the thoracic cavity to treat chylothorax, or to assist in
include preoperative placement of a fentanyl patch, ‘high’ sealing a leaking TDS. The physiological drain theory is
epidural anaesthesia using morphine (0.1 mg/kg) and inter- difficult to support logically, because the omental lymph-
costal nerve blocks using bupivacaine (1.5 mg/kg). As dis- atics drain back into the TDS. As mentioned above, primary
cussed above, the TDS is generally found on the right side pericardial disease or pericardial thickening in response to
of the caudal mediastinum in dogs and on the left side of chronic chylous effusion is thought potentially to elevate
the caudal mediastinum in cats. Thus, the entire right or caval pressure and contribute to chylothorax in some
left lateral thorax and abdomen (depending on species) is animals. Anecdotally, biopsy of a thickened pericardium
clipped and prepared for surgery. removed to treat persistent chylothorax revealed micro-
In dogs, a right eighth or ninth intercostal space scopic carcinoma. Ablation of the cisterna chyli is thought
thoracotomy is performed. The TDS lies between the to stimulate the formation of intra-abdominal lymphatic-
aorta and the azygous vein. Visualization of the TDS is ovenous anastomoses, bypassing the TDS.
often difficult, even if corn oil or cream has been fed Various combinations of thoracic duct ligation, peri-
immediately preoperatively; sympathetic nerves in the cardectomy, cysterna chyli ablation and omentalization are
caudal mediastinum can be confused with lymphatic now performed. The approach for thoracic duct ligation is
vessels. Identification of the TDS is facilitated by expo- generally too caudal to allow a safe pericardectomy, so an
sing an abdominal lymph node through a flank incision. A additional fifth intercostal space thoracotomy is required
single paracostal incision has also been described, allow- for pericardectomy, unless the procedure can be per-
ing access to the abdomen for lymph node injection and formed thorascopically through the initial intercostal thora-
the thorax, through the diaphragm, for thoracic duct liga- cotomy. The cisterna chyli ablation can often be performed
i
tion (Staiger et al., 2011). Usually, the easiest lymph node through the abdom nal approach used to access a mesen-
to locate is associated with the ileocolic junction. Once teric lymph node or lymphatic vessel for injection of methyl-
identified, a small volume (0.5–1 ml) of methylene blue is ene blue or contrast. The omentum can be identified and
injected into the node. The TDS will turn blue shortly after mobilized through the flank abdominal incision and passed
this injection is made. At this point, some surgeons into the thoracotomy via a small hole in the diaphragm.
cannulate an abdominal lymphatic vessel with a 20–24 G
over-the-needle catheter and perform a contrast lymph- Pleuroport placement: A pleuroport is a stainless steel
angiogram by injecting 1 ml/kg of water-soluble contrast subcutaneous access port that can be accessed percu-
agent diluted with 0.5 ml/kg of sterile saline into the lym- taneously using a Huber needle that is connected to a
phatic system. Although this allows identification of the silastic catheter placed in the pleural space. These
number and location of lymphatic branches in the caudal devices allow the pleural space to be drained safely with-
mediastinum, it requires intraoperative fluoroscopic or out the risk of lung injury associated with repeated
radiographic capabilities. needle thoracocentesis. They are, therefore, useful in sit-
The TDS is dissected and ligated using silk or Prolene uations where repeated thoracic drainage is anticipated
sutures. At this point a contrast lymphangiogram may be (i.e. failure or inability to control fluid production). The
repeated to help ensure ligation of all TDS branches. A patient is anaesthetized and the lateral thorax clipped. A
thoracostomy tube is placed, and the thoracic and abdom- small incision is made through the skin and lateral
inal incisions are closed in the routine manner (see thoracic musculature. A small window is made between
Chapter 11). the ribs to allow the fenestrated end of the silastic tube to
An ‘en bloc’ method for thoracic duct ligation without be fed into the pleural space. The other end is connected
the use of lymphangiography has been reported in dogs to the subcutaneous access port, which is sutured to the
and cats (Bussadori et al., 2011). The thoracotomy approach thoracic musculature in a subcutaneous pocket.
is similar to that described above. A separate flank incision
was not performed as mesenteric lymphan giography was Pleuroperitoneal shunting: This has been used to treat
not used in the series of cases reported. All structures chylothorax when thoracic duct ligation has failed. In this
dorsal to the aorta and ventral to the thoracic vertebral technique, a commercially available shunt catheter is
bodies were dissected and ligated en bloc, sparing the implanted and the owner pumps pleural fluid into the
sympathetic trunk. A subphrenic pericardectomy and peritoneal cavity.
omen talization were also performed. The results of this The patient is anaesthetized and placed in lateral recum-
procedure in a limited number of dogs and cats were similar bency. The lateral thorax and abdomen are clipped and
to those described for other techniques. prepared for aseptic surgery. The pleuroperitoneal shunt is
The thoracic duct can also be dissected thorascopi- placed into a bowl of heparinized saline and primed by
cally (Mayhew et al., 2012). This technique has the advan- repeatedly compressing the pump chamber. Vertical skin
tages of being minimally invasive and allowing a incisions are made over the seventh or eighth rib and the
minimally invasive pericardectomy and/or cisterna chyli 12th rib. The incisions are continued under the external
ablation to be performed in conjunction with thoracic abdominal oblique muscle and a tunnel is dissected
duct ligation. It requires two thoracoscopes and asso- between the two incisions at this level. The shunt is pulled
ciated towers. The surgeon and anaesthetist need to be through from the first incision to the second, taking care
experienced in thoracoscopic surgery and potentially that the afferent tubing is positioned towards the thorax
one-lung ventilation. and the efferent tubing towards the abdomen. The pump

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