Understanding and Managing Hepatic Microvascular Dysplasia in Dogs
Hepatic Microvascular Dysplasia (MVD), also referred to as
portal vein hypoplasia, is a congenital or inherited disorder affecting the microscopic blood vessels within a dog’s liver. In simple terms, the small portal veins are either
underdeveloped or absent, resulting in reduced blood flow into the liver. This can lead to diminished liver function, affecting the body’s ability to filter toxins, metabolize nutrients, and synthesize vital proteins.
What Causes MVD and Who Is Affected?
MVD is thought to be a
heritable condition most often found in
small dog breeds. Breeds such as Yorkshire Terriers, Shih Tzus, Miniature Poodles, and Cocker Spaniels are especially predisposed. While rare in large breeds and cats, it has been reported in some feline cases.
Signs and Symptoms of MVD
The clinical presentation of MVD can vary considerably. Some dogs will never show symptoms, while others may experience more noticeable health issues. Common signs include:
- Poor weight gain or developmental delays
- Reduced activity or dullness
- Vomiting and diarrhea
- Pica (eating non-food items)
- Increased thirst and urination
- Neurological signs like seizures or head pressing (in severe cases)
It's worth noting that these signs are usually
mild compared to dogs with macroscopic portosystemic shunts (PSS).
Diagnosis: How is MVD Confirmed?
Diagnosing MVD includes a combination of:
- Laboratory blood tests – May show mild anemia, low proteins, low glucose, and/or elevated liver enzymes.
- Urinalysis – May detect dilute urine or ammonium biurate crystals.
- Serum bile acid testing – Elevated postprandial bile acid levels suggest liver dysfunction.
- Protein C activity – Typically normal in MVD but decreased in larger shunt cases.
- Imaging scans – Ultrasound, CT, MRI, or nuclear scintigraphy can help rule out larger shunts.
- Liver biopsy – Required for definitive diagnosis. Multiple liver lobe samples increase the accuracy.
Management and Treatment Options
Although
MVD cannot be surgically corrected, most affected dogs can live normal lives with appropriate management. Treatment is generally
medical rather than surgical, focusing on minimizing the effects of impaired liver function.
Recommended treatments include:
- Dietary modification – Feed a prescription hepatic diet using restricted, high-quality protein (like soy or dairy protein).
- Lactulose – Reduces ammonia absorption in the gut.
- Antibiotics – Short-term use to manage intestinal bacteria (e.g., metronidazole).
- Hepatoprotective supplements – S-adenosylmethionine (SAMe), silymarin (milk thistle), vitamin E, and ursodeoxycholic acid.
- Probiotic support – Yogurt and commercial probiotics might support gut health, though scientific backing is limited.
Monitoring and Long-Term Outlook
Most dogs with MVD experience a
non-progressive form of the condition. Regular veterinary checkups monitoring:
- Liver enzymes
- Protein and ammonia levels
- Urinary health to prevent infections or stone formation
Improves the long-term outlook. Frequent bile acid testing is not always necessary, especially in asymptomatic dogs.
Breeding Considerations
Due to the suspected
polygenic inheritance pattern, breeding of dogs diagnosed with MVD is strongly discouraged. Even dogs with normal bile acid levels can carry the genetic trait and pass it to offspring. Genetic testing and responsible breeding practices are crucial for reducing MVD prevalence.
Conclusion
While there is
no surgical cure for hepatic microvascular dysplasia, many cases remain mild and manageable through medical intervention and dietary adjustments. With early diagnosis and proper care, dogs affected by MVD can enjoy a normal life expectancy and good quality of life. Responsible breeding practices and routine veterinary monitoring are key to managing this congenital condition.
