Information on other Diseases


What is Protein Losing Enteropathy?
What is MVD?



What is Protein Losing Enteropathy:

Excessive loss of plasma and proteins into the gastrointestinal (GI) tract is called protein-losing enteropathy. It can result from any condition that damages the lining of the GI tract. Protein-losing enteropathies that are thought to have an inherited component include intestinal lymhangiectasia, immunoproliferative enteropathy , and protein-losing enteropathy and nephropathy in the soft-coated wheaten terrier. The latter condition is thought to be related to adverse food reactions, and there is also loss of protein from the kidney (see also familial renal disease).

How is protein-losing enteropathy and nephropathy inherited? The inheritance may be autosomal recessive.

What breeds are affected by protein-losing enteropathy and nephropathy? soft-coated wheaten terrier

What does protein-losing enteropathy and nephropathy mean to your dog & you? Your dog may fail to gain weight or may progressively lose weight. The loss of protein into the bowel causes loss of fluid from the circulation into the limbs, the abdomen, or the chest. Your dog's legs and/or abdomen may appear swollen and he/she may have trouble breathing. There may be a chronic persistent or intermittent diarrhea due to the loss of protein, fluid and fat into the bowel. Loss of protein from the kidney will cause increased urination and drinking in your dog.

How is protein-losing enteropathy and nephropathy diagnosed? If your dog has the signs described above, your veterinarian will likely suspect one of the diseases that result in loss of proteins into the gut. Laboratory tests and an intestinal biopsy are necessary to diagnose the specific cause.

How is protein-losing enteropathy and nephropathy treated? This condition can not be cured but it can generally be well-managed by you and your veterinarian. The major goal of therapy is to reduce the loss of proteins into the intestine, to restore normal protein levels in your dog. This is done through diet, and medication to reduce inflammation in the intestinal wall. An ideal diet for dogs with protein-losing enteropathy contains minimal fat, and an ample quantity of high-quality protein. There are commercial prescription diets available which fulfill these requirements, or your veterinarian can give you information to prepare a low-fat diet at home. In either case, you will need to supplement your dog's diet with fat-soluble vitamins, due to the poor absorption of fat that occurs with this condition. Corticosteroids may help to reduce inflammation, and thereby reduce loss of protein and associated diarrhea.

Breeding advice
Affected dogs should not be used for breeding. Given that the inheritance is thought to be autosomal recessive, parents (considered carriers) and siblings (suspect carriers) should not be used for breeding either.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources
Burrows, C.F., Batt, R.M., Sherding, R.G. 1995. Diseases of the small intestine. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal
Medicine. p. 1224-1225. W.B. Saunders Co., Toronto.
Williams, D.A. 1998 Protein-losing enteropathy Proc. 16th ACVIM Forum pp 419-421
Copyright C 1998 Canine Inherited Disorders Database. All rights reserved. Revised:
This database is a joint initiative of the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association.

Paws


What is MVD?

When the Liver Isn’t Getting Enough Blood

August 07, 2000
Written by: Celeste A. Clements, DVM, Diplomate ACVIM

Veterinarians and owners of small breed dogs are on the lookout for signs of a liver problem that has been recognized by pathologists for some 15 years, but only recently by veterinary internists.

Hepatoportal microvascular dysplasia, or MVD, is a congenital disorder of the liver’s blood supply. Dogs that inherit this problem may become quite ill: coma, seizures, and bizarre behavior are among the more extreme manifestations of the disease. The problem is especially prevalent in Cairn and Yorkshire terriers.

Dogs that have MVD don’t get an adequate supply of blood to the liver. A healthy liver detoxifies and purifies blood returning from the abdominal organs. Blood enters the liver through the portal vein, which branches throughout the liver lobes via seven major tributaries. If blood supply to the liver is abnormal or insufficient, the liver will not grow properly, and its function will be affected—and how bad the problem is really depends on the extent of the deformity. Blood that fails to enter the liver properly is diverted or "shunted" through alternate routes.

An elusive disease

MVD isn’t the only type of congenital liver abnormality resulting from improper blood supply. With a portosystemic vascular anomaly—or PSVA—the blood supply may be visibly abnormal because it bypasses all or a portion of the liver. The difference with MVD is that the abnormality is apparent only at the microscopic level—which is why veterinarians sometimes have a hard time tracking it.

The disease is so subtle that the veterinarian may not be able to detect it. If the dog does show signs of illness, they usually include increased thirst and urination, intolerance of food, or changes in behavior that may reflect the influence of dietary toxins and byproducts of metabolism on the brain. Hepatic encephalopathy, a condition that results from an excessive blood level of metabolic byproducts that are normally filtered out by the liver, is observed in the majority of patients with substantial blood shunting.

Additional signs include depression or confusion, incoordination, apparent blindness, and even seizures and coma. Dementia or bizarre behavior after eating is a common occurrence in puppies with "shunts;" however, more subtle signs may be evident in canine patients with MVD.

Investigating MVD

Bile acid profiles have become a popular noninvasive test for detecting circulatory and other functional disturbances of the liver. The level of bile acids in the fasting and fed, or postprandial state, assessed together offer a useful prediction of clinically significant liver disease.

Bile acids are a component of bile, produced by the liver, and stored in the gallbladder. When the gallbladder empties, in response to chemical or hormonal signals stimulated by eating, bile enters the intestinal tract to aid in digestion. Along with other metabolic byproducts, a significant amount of the bile salts are reabsorbed into the bloodstream at the termination of the small intestine, the ileum. Subsequently, they pass into the portal circulation, destined for the liver.

In dogs with healthy livers, the bile salts are extracted from the blood and recirculated. However, the level of bile acids will be high if the patient has impaired hepatoportal circulation, reduced liver mass, or bile retention.

A high level of bile salts doesn’t mean the dog has MVD, though. There is considerable overlap between different liver diseases, so additional diagnostics are needed to differentiate between them, to include sonographic imaging, nuclear scintigraphy or dye studies, and, frequently, liver biopsy.

When a dog has an abnormal circulation of blood to the liver, the presence of shunting can be assessed by noninvasive means, including nuclear scintigraphy. With this procedure, a radioisotope-labeled enema is administered. This radioisotope is taken up by circulation in the colon and the labeled blood is delivered to the liver in normal dogs and to the heart in dogs that have shunts. Computer technology allows for the comparison of labeled blood’s entry into the liver or the heart. Estimates of the shunt fraction are relatively reliable, but the technique rarely localizes the abnormal circulation. If the shunt fraction is less than or equal to 15 percent, then it’s unlikely that the portosystemic vascular anomaly is surgically correctable.

A dye study can provide a definitive diagnosis of a problem with circulation of blood to the liver. In the case of MVD, a dye study test will show uneven distribution of contrast within liver tissue, blunted branches of the portal vein, and persistence of contrast in the liver tissue. Such procedures are performed on an anesthetized patient, most commonly in connection with surgery to visualize or sample the liver. However, if an anomalous blood vessel is identified grossly, contrast studies, termed portography, are rarely performed.

Treatment options

Surgical correction of the shunting vessel, through banding or ligation, is successful in the majority of dog patients, if performed before two years of age. A more normal pattern of blood flow is achieved, with improved perfusion of liver tissue and improved liver function, but microscopic circulatory changes may persist in those patients, preventing establishment of a completely normal state.

Unlike dogs with PSVA, dogs with MVD cannot enjoy correction of the liver dysfunction. Treatment of dogs showing signs of disease focuses on feeding diets restricted in dietary protein, using oral antibiotics to curtail intestinal bacterial growth, and offering lactulose to reduce intestinal absorption of ammonia, one of the important contributions to hepatic encephalopathy. Effective control of signs should permit a good quality of life for most dogs. Some will still develop progressive liver dysfunction, though, with portal hypertension and subsequent accumulation of abdominal fluid.

No treatment is required for asymptomatic patients, but all dogs with MVD may be at higher risk for adverse reactions to medications processed by the liver. Discretion is wise when administering prescription or over-the-counter medications, and when planning for anesthesia. It is unclear whether MVD predisposes patients to other forms of liver disease, such as inflammatory conditions or infections.

Catching it early

Early identification of dogs with MVD is ideal. It’s important to prevent breeding and perpetuation of the disease and to distinguish the disorder from other diseases that might cause liver dysfunction in later life. Cairn terriers and Yorkshire terriers may be considered a high-risk population; MVD also has been documented in other small breeds, such as the miniature schnauzer, Lhasa apso, dachshund, Maltese, bichon frise, and poodle.

The problem should be suspected in pups or young small breed dogs that have repeatedly elevated serum bile acids but are otherwise well. Noninvasive scintigraphy makes sense for patients suspected of MVD or PSVA, although it may not be readily available in all locales. Further, the test cannot definitively verify or rule out microscopic abnormalities, only gross shunting. Only a liver biopsy of reasonable size and good quality can definitively diagnose MVD.

Liver biopsies are safely performed in the vast majority of patients, but the risks should be assessed for each patient and compared to the potential benefits. While a liver biopsy may be indicated for symptomatic patients with high bile acids, it is much more difficult to justify this procedure for dogs that have only abnormal test results. If spaying is planned for female dogs at risk, then a visual inspection of the liver and portal circulation and liver biopsy may be considered.

In some cases, MVD remains a tentative diagnosis, which seems reasonable provided no surgically treatable problem is overlooked. As one of many diseases that are hard to "pin down," MVD continues to be investigated by veterinary researchers.



Hepatic Microvascular Dysplasia is a condition in which there is mixing of venous blood and arterial blood at the microscopic levels in the liver. If you search for information on this condition, it is also called hepatoportal microvascular dysplasia so you may find information using either name. This condition has been recognized in a number of small dog breeds but seems especially prevalent in Cairn terriers and Yorkshire terriers.

It is likely that most dogs with this condition have no readily apparent clinical signs associated with the microvascular dysplasia and are diagnosed when bile acid response testing is done to rule out liver disease for some reason. Unfortunately, some dogs with this condition do have clinical signs, which can include seizures or other central nervous system disorders, gastrointestinal problems or urinary tract disease associated with ammonium biurate cystals in the urinary tract, which form due to the liver problems.

Abnormal bile acid response testing usually provides the initial suspicion that this disease is present. High bile acid levels can occur with portosystemic shunts, as well. It is necessary to rule out that possibility when considering the possibility of hepatic microvascular dysplasia. Liver biopsy adds further evidence for the presence of this condition, in part by ruling out other liver diseases.

When dogs have microvascular dysplasia without clinical signs, their prognosis is very good. In many instances there is not a need for therapy. In dogs that are diagnosed because they have clinical signs, it is often possible to manage the signs through the use of dietary therapy and medications. The dietary therapy is aimed at reducing excess protein in the diet and the medications, including lactulose and antibiotics such as neomycin or metronidazole, which are used to lower ammonia levels in the digestive tract and thus in the body. The prognosis is variable for patients who have clinical signs from hepatoportal microvascular dysplasia. Some dogs do well with therapy and live normal, or nearly normal, life spans. Others have worsening of the clinical signs over time. I do not know of a method for predicting how well an individual patient will do.

There are a number of reduced protein diets that might be helpful, including Hills k/d (tm) and l/d (tm) diets, Purina's NF diet and others. Lactulose dosage is adjusted to individual patient's needs by using it to obtain a soft but formed stool. Neomycin is usually given at a dosage of 22mg/kg of body weight twice a day and metronidazole at 7.5mg/kg twice a day. This is a lower metronidazole dosage than is used for many other conditions. I have seen recommendations for the use of other antibiotics but these two are the most commonly mentioned ones.

Paws



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