What is chylothorax?
Chyle = a milky fluid that contains a high concentration of fat (trigycerides)
Thorax = chest
Chylothorax is the accumulation of chyle within the chest cavity. The majority of chyle comes from the intestines following absorption of fat from an ingested meal. The fat enters the lacteals (small lymph vessels) in the wall of the intestine and then is transported to the regional lymphnodes, passes through larger lymph vessels and joins the largest lymph vessel in the abdomen called the cisterna chyli. The location of the cisterna chyli is along side the largest artery in the abdomen called the aorta at the level of the left kidney. From there the lymph fluid moves through the chest via the thoracic duct, which finally joins a large vein in the chest called the vena cava. Thus the lymph fluid is delivered into the blood stream.
Chylothorax result from leakage of lymphatic fluid in the chest cavity through leaky lymph vessels in the chest. Obstruction to flow of lymph fluid can be due to increased pressure in the thin-walled lymph vessels. The obstruction of the lymphatic flow can be due to heart disease, cancer with the chest, fungal infections in the chest, heartworm disease, congenital defects, trauma, chronic vomiting, coughing, diaphragmatic hernia, twisted lung lobe, and a blood clot in the veins in the chest. Although rupture of the thoracic duct logically seems like it should be the most common cause of chylothorax, studies have shown that the thoracic duct is grossly intact in these cases. Even experimental tearing of the thoracic duct results in only transient chylothorax that spontaneously resolves in about 2 weeks. In most patients that have a work-up for chylothorax, a primary cause of this problem is not found therefore it is called idiopathic chylothorax.
Sex nor age seem to be a factor in the development of chylothorax. A number of breeds are predisposed to this condition and include cats, Afghans, and Mastiffs. Shallow, rapid respirations, and coughing are typically the most common presenting signs. Other signs may include loss of appetite, weight loss, gagging, lethargy, regurgitation, vomiting and exercise intolerance.
Chest x-rays will always show the accumulation of fluid in the chest cavity and collapse of lung lobes. Fluid collected from the chest with a needle is analyzed and will have a high level of trigycerides (fat) and can have a mixture of white and red blood cells (photo right shows typical appearance of chyle). Other testing that commonly is done includes repeat chest x-rays after draining the fluid from the chest, ultrasound of the abdomen and chest, and blood tests (complete blood count and chemistry profile, heartworm test, fungal titers if indicated).
Before surgery is considered, a low fat diet and a medication called Ruitin may be tried. If the problem resolves...great. The diet and Ruitin should be continued indefinitely. Intermittent removal of fluid from the chest with a needle will be necessary until the medical therapy becomes effective. Unfortunately, successful medical therapy is uncommon. If a patient has an underlying cause of chylothorax, treatment of the primary disease process (fungal infection, cardiomyopathy, etc) should resolve the accumulation of chyle in the chest.
Preparation for surgery
The pet should be fasted prior to surgery, as instructed by the surgical team. Water is usually permitted up to the time of admission to the hospital. The surgical team should be informed of any medications that your pet is currently receiving. If there is an accumulation of fluid in the chest that is causing breathing difficulties, fluid will be removed with a needle or catheter prior to anesthesia.Just prior to surgery, your pet will receive a sedative, have an intravenous catheter placed for the administration of intravenous fluids and intravenous medications, be induced under general anesthesia with medication(s), and have a breathing tube (endotracheal tube) placed to allow delivery of oxygen and gaseous anesthesia. While under general anesthesia, the pet's breathing will be assisted with a ventilator and vital parameters such as heart rate, respiratory rate, core body temperature, blood pressure, oxygenation of the blood (pulse oximetry), exhaled carbon dioxide (capnography), and heart rhythm (EKG) will be monitored to ensure the pet's well being. Pain will be controlled both during and after surgery with analgesics (pain-controlling medication). Please note that each surgical and anesthesia team may elect to chose a different, but effective analgesia protocol.
Surgical ligation of the thoracic duct is an important part of the therapy and involves either an open approach to the duct with a sizeable incision , or performed with a minimally invasive technique called VAT surgery (Video-Assisted Thoroscopic) surgery. This procedure involves placing a thin telescope within the chest cavity and utilizing long forceps to isolate and staple the duct closed. Other techniques that have been employed include ablation (tearing out) of the cisterna chyli within the abdomen or removal of the sac that surrounds the heart (pericardectomy). The pericardectomy has been recommended as it reduces the venous pressure, thus allowing the lymphatic flow to be improved; however, a recent study has not really shown a true decrease in venous pressure. Recently, MacInulty has shown that thoracic duct ligation and ablation of the cisterna chyli is slightly more effective than that performing thoracic duct ligation and pericardectomy. Ultimately, what is believed to happen with time is that lymph vessels develop new connections to the veins in the abdomen instead of having the fluid flow through the thoracic duct, thus resolving the chylothorax. In summary, your pet may have an incision that is made in the abdomen and the chest, or the procedure may be done with the assistance of a thoracoscope.
Care after surgery
Most pets having this type of surgery will stay in the hospital at least 3 to 5 days to monitor the pet for breathing difficulties. While in the hospital, intravenous fluid therapy likely will continue until the pet goes home. Oxygen therapy may be needed via a nasal catheter. A chest tube that is placed at the time of the surgery is used to evacuate fluid from the chest. The chest tube is removed once the fluid production is minimal.
At home, medication to control pain after surgery should be administered for a few days. Antibiotics are commonly prescribed, but only may be needed for a week or two. Exercise should be restricted for two weeks, but leash walks are generally permitted. A follow-up examination should be done in 2 weeks after surgery to evaluate the healing process.
The prognosis for patients with idiopathic chylothorax which ligation of the historically has been fairly poor with only about 50% of dogs and 25% of cats responding to treatment. With the addition of cisterna chyli ablation or pericardectomy, about 80% of patients have resolution of the chylothorax and go on to live a normal life.
- McAnulty JF. Prospective comparison of cisterna chyli ablation to pericardectomy for treatment of spontaneous chylothorax the dog. Vet Surg 2011, 40:926-34.
- Da Silva CA, Monnet E. Long-term outcome of dogs treated surgically for idiopathic chylothorax: 11 cases (1995-2009). J Am vet Med Asoc 2011, 239:107-13.
- Allman DA, Radlinsky MG et al. Thoroscopic thoracic duct ligation and thoroscopic pericardiectomy for treatment of chylothorax in dogs. Vet Surg 2010, 39:21-7.
Frequently Asked Questions After Surgery
When should my dog have the first bowel movement after surgery?
- Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
- Reasons that a dog will not have regular bowel movements after surgery include:
- The dog has been fasted prior to surgery
- Dogs do not eat well during the hospital stay
- They frequently do not eat well when they go home
- They are fed highly digestible food that produces little stool
- Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
- If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
- Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable
My pet had surgery and will not eat. What can be done?
- Most pets will not eat their regular dog food after surgery, especially if it is kibble.
- Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source. The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked). The carbohydrate can be pasta, potato or white rice.
- Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
- Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
- Try Hill's A/D diet available at most veterinary hospitals
- Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
- Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
- Remember that most pets will not eat the first day or two after they get home from surgery
- Offer smelly foods that contain fish such as tuna or smelly cat foods
- Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
- Hand feeding: with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
- Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
- Some cats will only eat dry food, try kibble if your cat normally has been fed that food
- Petting and stroking your cat frequently will help to stimulate appetite
- Remember that most pets will not eat the first day or two after they get home from surgery
- Appetite stimulants such as cyproheptadine may be helpful
- If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop
My pet is vomiting. What can be done?
- The first thing for you to discern is whether your pet is vomiting or regurgitating. Both will result in fluid or food being brought up. Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus. Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled. Usually the regurgited material will be clear or brown colored fluid.
- Next is to identify the cause of the vomiting or regurgitation.
- Causes and treatment of vomiting after surgery
- When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
- Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery. In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart. Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to. The antibiotic in some cases may be changed to a different one, or may be discontinued.
- Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days.
- An uncommon cause of vomiting after surgery is internal organ failure. Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
- If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present. Do not ignore this sign.
- Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days. In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days. Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats. You should always consult a veterinary healthcare professional before administering medication.
- Causes and treatment of regurgitation after surgery
- The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia. Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis. This results in poor motility of the esophagus, therefore water and food will accumulate in this structure. In most cases, esphagitis is self-eliminating and will resolve within two or three days.
- If the esophagitis is severe the esophagus may develop one or more strictures. A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week. This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope). If an esophageal stricture is chronic surgery is needed.
- Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other). Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.
How do I know that my dog is in pain following surgery?
- Signs of pain include
- biting if you get near the surgical site
- grimacing (lips are pulled back and the the dog looks anxious)
- tragic facial expression
- restlessness and unable to sleep; pacing
- if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
- the worst pain will be for the first 2 to 3 days after surgery
What can I do to control my dog's pain?
- Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
- Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
- If an orthopedic surgery has been done cold packing the surgical site may be helpful
- A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack. An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern. Cooling the surgical site helps to numb the area.
How do I know that my cat is in pain following surgery?
- Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
- Signs of pain in a cat include the following:
- biting if you get near the surgical site
- growling or deep cry
- not wanting to eat
- hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)
What can be done for pain at home for my cat?
- Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
- Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
- Anti-inflammatories can be used, but the dose is much less than dogs
Is it okay for my pet to lick the incision?
- If a dog licks the incision, the healing process may be delayed.
- Licking can remove stitches and cause the incision to open
- Licking can become a severe habit that is difficult to break
- Licking can cause infection as the mouth has many bacteria
- Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
- To stop your pet from licking the following can be tried:
- Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
- Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
- A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
- A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
- Bitter apple can be applied around the incision; many dogs will continue to lick after application of this topical
- Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
- Antipsychotic medication in some cases is needed