Reviewed by: Paula Simons, DVM
Most dog owners are aware of health changes in their dogs. As experienced dog owners, we have a pretty good sense of whether something warrants an immediate trip to the veterinarian or not.
Unfortunately, bile duct obstructions might not be that obvious in the early stages.
One of the telltale signs that something is going wrong somewhere in the liver or gallbladder is the development of jaundice.
Jaundice occurs when the liver doesn’t excrete bilirubin correctly. Bilirubin (a yellowish pigment that is made during the breakdown of red blood cells) is supposed to pass through the liver so it can be excreted out of the body.
Jaundice can occur in a dog’s eyes, skin, and mucous membranes. You may be able to detect the discoloration wherever the skin is bare.
If there’s a blockage (bile duct obstruction), the bilirubin builds up and eventually finds its way into the bloodstream. The skin and mucous membranes turn yellow from the pigmented deposits left behind.
In this post, we will explain what a bile duct obstruction is, signs to look for, causes, diagnosis, and treatment options.
Dog Breeds Most at Risk of Bile Duct Obstructions
Since pancreatic disease is the most common cause of bile duct obstructions in dogs, it stands to reason that dog breeds most susceptible to pancreatic disease are also more at risk of obstruction.
Any dog can develop pancreatic disease. However, the breeds most susceptible include:
- Miniature Schnauzers
- Cocker Spaniels
- Poodles
- Yorkshire Terriers
- Shetland Sheepdogs
Again, it’s important to note that pancreatic disease can occur in any breed. Bile duct obstructions can be caused by a number of things. Pancreatic disease is just one reason.
What is a Bile Duct Obstruction
A bile duct obstruction (extrahepatic biliary tract obstruction) occurs when the normal flow of bile secretions is blocked from leaving the liver and entering the intestines.
Normally, bile flows from small ducts in the liver to larger ducts. Eventually, it ends up in the gallbladder where it’s stored until digestion occurs. Anything that stops the bile from entering the first part of the small intestine (known as the duodenum) is considered an obstruction.
There are two main bile ducts in the liver: the right hepatic duct and the left hepatic duct, as shown below.
Bile Ducts
The biliary tree is a group of tubes that collect bile. The common bile duct starts where the liver ducts and gallbladder join, and ends at the small intestine.
Source: www.cancer.gov (definitions)
Bile
Bile is a highly alkaline, yellow-greenish fluid that forms in the liver. Once formed, the liver secretes bile into the gallbladder until food is digested. In dogs, the process of eating triggers the release of bile into the duodenum.
The main purposes of bile are to excrete bilirubin and to break down fats during digestion.
If an obstruction prevents bile from performing these tasks, it builds up in the blood system. It’s this build-up that causes the skin to turn yellow (jaundice).
What Causes Bile Duct Obstructions in Dogs?
Dogs who like to swallow things other than their own food (toys, bones, rocks, socks, trash, etc.) are at risk of bile duct obstruction. These objects can get trapped in the small intestine, where they also end up blocking the bile duct.
Other causes of bile duct obstruction can include:
1. Pancreatitis
Pancreatitis is an inflammation of the pancreas. The pancreas is a gland located along the stomach and the first part of the small intestine.
Pancreatitis causes various levels of inflammation in the pancreas. In simple terms, inflammation of the pancreas can block the pancreatic duct. This causes what’s known as an extrahepatic biliary tract obstruction.
Pancreatitis in dogs is classified as either “acute” or “chronic.” Sometimes, there are even atypical cases that don’t seem to fall neatly into either category.
Signs of acute and chronic pancreatitis in dogs include:
- Vomiting
- Abdominal pain
- Abdominal distention
- Diarrhea
- Loss of appetite
- Dehydration
- Weakness/lethargy
- Fever
A dog might present to a veterinarian with acute, or sudden, signs of pancreatitis. If the dog has repeated episodes, it’s then considered chronic.
2. Gallstones (Cholelithiasis)
Cholelithiasis is a medical condition that occurs when stones form within the gallbladder. These “stones” are made up of parts of the bile, including:
- Cholesterol
- Bilirubin
- Calcium
Gallstones can form if the gallbladder isn’t functioning properly or if there’s something wrong with the bile. Abnormal bile can occur if the dog has:
- High cholesterol
- High levels of bilirubin
- Triglycerides
- Poor diet (too much fat or not enough taurine and protein)
Gallstones don’t always cause problems for the dog. Other times, however, they can lead to cholangitis, which is an inflammation of the biliary tree (mentioned above).
Diseases associated with the liver, gallbladder, and/or bile duct system can be confusing for pet owners because these diseases can have vague symptoms.
Cholangitis and Cholangiohepatitis in Cats
Jacqueline Brister, DVM
https://veterinarypartner.vin.com/default.aspx?pid=19239&id=9644369
Date Published: 05/14/2020
3. Gallbladder Mucocele
The gallbladder sits between the liver lobes and acts as a reservoir for bile. A canine mucocele (pronounced mew-coh-seal) forms when the gallbladder lining produces abnormally thick mucus.
The accumulation of this thick, sludge-like mucus will stop the normal flow of bile from the gallbladder into the small intestines.
If the mucus continues to accumulate, it causes the gallbladder to expand. The more it expands, the greater the risk of a gallbladder rupture.
If an obstructed gallbladder ruptures, it can be fatal.
4. Cholecystitis (Inflammation of the Gallbladder)
Dogs can develop gallbladder inflammation from bacterial infections, liver damage, cancer, or a blocked bile duct.
An inflamed gallbladder can lead to a clogged bile duct, and a clogged bile duct can lead to an inflamed gallbladder.
Clinical signs of cholecystitis include:
- Lethargy
- Loss of appetite
- Nausea
- Fever
- Abdominal pain
5. Tumors
Tumors of the liver and bile ducts are rare in dogs and account for less than 2% of all canine neoplasms. Source: Canine Liver/Bile Tumors – Long Island Veterinary Specialists.
Liver and bile tumors are known as hepatobiliary tumors. They are divided into one of four types:
- Hepatocellular tumors (20% – 60% risk of spread to other organs)
- Bile duct tumors (80% risk of spread)
- Neuroendocrine tumors (90% risk of spread)
- Primary sarcomas (low-grade tumors metastasize in less than 20 – 25% of cases).
The dogs who develop these tumors are typically older dogs. Unfortunately, most neoplasms (tumors) are malignant with a high risk of spreading, depending on the type.
Dogs with liver and/or bile duct tumors usually present with clinical signs of liver disease at the time of diagnosis.
6. Liver Disease
Liver disease is a broad term for several conditions that cause damage or inflammation. A dog may have primary liver disease or liver disease that is caused by something else. It can be caused by bacterial infections, exposure to toxins, viruses, or congenital birth defects.
Types of liver disease in dogs include:
- Hepatitis
- Cirrhosis
- Portosystemic shunt (PSS or liver shunt)
- Copper storage disease
- Fatty liver disease (most common in cats)
- Cancer (hepatocellular carcinoma is the most common)
7. Primary Biliary Cholangitis (Cholangiohepatitis)
This condition causes inflammation of the bile duct system. In most cases, it’s caused by bacterial or viral infections that find their way from the gallbladder and bile ducts into the small intestine.
Clinical signs of cholangiohepatitis include:
- Decreased appetite
- Fever
- Weight Loss
- Vomiting
- Diarrhea
- Jaundice
- Abdominal fluid accumulation
Dogs diagnosed with this condition are usually treated with broad-spectrum antibiotics. Some dogs may need to be hospitalized for intravenous fluids and other medical support.
8. Parasitic Infection
Liver fluke infections are rare in dogs, but can occur in areas where the problem is endemic. Dogs can become infected from eating raw fish that carry the parasite.
In severe cases, liver damage can occur.
9. Blunt Trauma
Blunt trauma is a type of injury that happens when you hit your body or something else hard.
Signs of a Bile Duct Obstruction in Dogs
There are a number of symptoms that can accompany a bile duct obstruction. Some dogs may have many symptoms, and some may only have vague symptoms. The following are some of the more common signs of a bile duct obstruction.
- Progressive tiredness
- Jaundice
- Excessive hunger
- Bleeding disorders
- Weight loss
- Pale colored stools
- Orange tinted urine
Diagnosis of Bile Duct Obstruction in Dogs
There are a few things that may lead a veterinarian to believe your dog has a bile duct obstruction. Dogs who already have problems with their pancreas, gallbladder, or liver are especially at risk.
Diagnosis isn’t always easy. Some biliary system disorders, such as extrahepatic biliary duct obstruction (EHBO) from stones, tumors, pancreatitis, inflammation, mucocele, and perforation, can cause vague clinical symptoms.
There are a number of tests that can be done to get a definitive diagnosis. The following are examples of these tests.
Physical Examination
The veterinarian will first conduct a physical exam to check for signs of jaundice.
Abdominal Radiographs
Abdominal radiographs are x-rays that produce images of the organs in the abdominal cavity. This test can help detect abnormal liver size, may detect irregular liver borders, calcified gallstones, obstructions, perforations, and tumors.
“Imaging technique of choice is abdominal ultrasound because radiography has been proven to be too insensitive for the diagnosis of biliary diseases”
citation:
Canine Biliary Tract Diseases: How to Reveal and Treat Them
World Small Animal Veterinary Association World Congress Proceedings, 2007
Thomas Spillmann, Dipl. vet. med., Dr. med. vet.
Professor of Small Animal Internal Medicine, Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki
Finland
Abdominal Ultrasound
Ultrasound is considered the “gold standard” in diagnosing problems with the gallbladder. If the gallbladder is ruptured, the dog will require emergency surgery.
Complete Blood Count
Blood tests can help determine if the dog is anemic or has evidence of systemic inflammation or infection.
Chemical Blood Profile
A chemical blood profile will measure liver enzymes and can detect increased levels of bilirubin.
Urinalysis
Veterinarians can also detect elevated levels of bilirubin through a urinalysis.
Stool Sample
Dogs with unusually pale stools may be suffering from an excess of bilirubin.
Bilirubin is the pigment that breaks away from red blood cells as they degrade. It’s what gives your dog’s stool its dark color. If your dog’s stool is unusually pale, it could mean that there is a bile duct obstruction preventing bile (which contains bilirubin) from circulating properly.
Blood Coagulation Test
The veterinarian may perform a test to see if your dog’s blood is clotting properly.
Treating Bile Duct Obstruction in Dogs
The treatment of a diagnosed bile duct obstruction starts with stabilization. This includes the administration of IV fluids and other supportive therapy. Broad-spectrum antibiotics may be prescribed to control infection.
Further treatment plans will depend on the severity and cause of the obstruction. If cancer is found, surgical intervention will be required.
The most common cause of bile duct obstruction in dogs is due to pancreatitis. In some cases, treatment of the pancreatitis can resolve the issue. In severe cases, surgery may be recommended.
Endoscopic Retrograde Cholangiography (ERCP)
ERCP can be used to diagnose and treat problems in the liver, gallbladder, bile ducts, and pancreas. The procedure involves inserting a specialized tube into the bile duct. This helps release the buildup of bile. When used in combination with x-rays and an endoscope (a long, lighted tube), it can help find:
- Bile duct obstruction
- Stones
- Fluid leakage from the bile or pancreatic ducts
- Narrowing of the pancreatic ducts
- Tumors
- Infection of the bile ducts
Surgery
In severe cases, surgery may be recommended. Cholecystectomy is the treatment of choice for dogs with gallstones or mucocele (benign, mucus-filled cyst).
Cholecystectomy involves the removal of the gallbladder. Although gallbladders can be treated with medical management (medication and diet), it will need to be removed if it is obstructing the flow of bile.
Hepatic ducts are considered the most difficult to resolve and may require duodenotomy (incision of the duodenum), cholecystostomy (incision in the gallbladder to facilitate placement of a tube for drainage), or choledochotomy (incision in the common bile duct).
This allows access to the obstruction, where removal of biliary sludge (thickened mucus) can be performed.
If the dog has a biliary tree infection, they are at risk of going into shock during surgery. This is especially true for cats.
Medical Management
Liver supplements like Denamarin may be prescribed. Denamarin supports healthy liver function. Ursodiol, an agent used to improve bile flow, may also be prescribed.
Medical management can also include the use of antibiotics and pain medication.
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Summary
There are many causes of bile duct obstruction in dogs. However, the main cause is usually related to pancreatic disease. The signs of an obstruction will vary depending on where the obstruction is and the severity.
Any signs of skin yellowing (jaundice), weight loss, fatigue, vomiting, diarrhea, or stomach bloating need to be brought to a veterinarian’s attention asap.
Remember that the signs noted in this post can be related to a number of issues.