Treating Microvascular Dysplasia in Dogs: A Complete Guide
Microvascular dysplasia (MVD), also known as portal vein hypoplasia, is a congenital liver condition that affects the microscopic blood supply within the liver, leading to reduced portal perfusion and impaired liver function. It's most commonly seen in small breed dogs such as Yorkshire Terriers, Shih Tzus, and Maltese. While MVD can be asymptomatic, it may result in various mild to severe clinical signs, prompting veterinary assessment and tailored treatment.
Understanding Microvascular Dysplasia (MVD)
MVD involves underdeveloped or absent small portal veins within the liver, leading to decreased delivery of nutrients and reduced detoxification. Unlike macroscopic portosystemic shunts, MVD involves microscopic abnormalities and is typically nonprogressive.
Breeds at Risk
While any dog can develop MVD, it is particularly prevalent in small breeds:
- Yorkshire Terriers
- Shih Tzus
- Maltese
- Miniature Poodles
- Dachshunds
It is rarely found in cats and large breeds but has been reported.
Symptoms of MVD
Many dogs show no signs, but in symptomatic cases, observed issues may include:
- Poor weight gain and small stature
- Gastrointestinal upset (vomiting, diarrhea)
- Behavioral changes and neurological signs (e.g., seizures)
- Increased thirst and urination
- Urinary tract infections or stones
Diagnostic Approaches
Diagnosis of MVD relies on a combination of clinical assessments and diagnostic tests. These include:
- Bloodwork: Mild anemia, low albumin, low BUN, and mildly increased liver enzymes may be present.
- Urinalysis: Presence of dilute urine or crystals.
- Bile Acid Testing: Elevated post-meal bile acids suggest MVD.
- Protein C Activity: Typically normal in MVD, unlike portosystemic shunts.
- Imaging: CT, ultrasound, or MRI to exclude large shunts.
- Liver Biopsy: Required for definitive diagnosis; taken from multiple lobes to increase accuracy.
Treatment Options
There is no surgical treatment for MVD itself. Instead, medical management is tailored to the individual dog's symptoms and laboratory values:
1. Dietary Management
- Protein restriction: Use highly digestible, low-purine proteins (e.g., dairy, soy).
- Prescription hepatic diets: Ensure needed nutrients and controlled protein levels.
2. Managing Ammonia Levels
- Lactulose: Reduces ammonia absorption in the gut.
- Antibiotics (e.g., metronidazole): Used short-term to reduce ammonia-producing bacteria.
3. Liver Support
- SAMe, silymarin, vitamin E, ursodeoxycholic acid: May offer hepatoprotective benefits.
- Probiotics and yogurt: To support digestive health, although evidence is limited.
4. Ongoing Monitoring
Though MVD is typically nonprogressive, routine monitoring is important:
- Track liver enzymes, protein levels, and ammonia periodically.
- Observe for clinical changes indicating complications.
Management of Concurrent Shunts
In cases where MVD occurs with a visible portosystemic shunt, the shunt may be surgically addressed. However, MVD itself remains medically managed as it's not surgically correctable.
Prognosis
Most dogs with MVD live a normal life span, especially if asymptomatic. Proper management in symptomatic cases can control clinical signs effectively.
Breed-Specific Considerations
Because MVD has a hereditary component and follows a possible polygenic inheritance pattern, breeding affected dogs is strongly discouraged. Even asymptomatic carriers can produce offspring with clinical disease.
Key Points to Remember
- MVD mostly affects small breed dogs and is often identified early in life.
- Diagnosis involves bile acid testing, imaging, and liver biopsy.
- Management includes dietary modification, lactulose, and occasional antibiotics.
- Liver supplements may help, but benefits in asymptomatic dogs are unclear.
- Ongoing monitoring and avoiding breeding are essential considerations.
By working closely with a veterinarian familiar with MVD, dog owners can ensure proper care and long-term health for their pets.
