Understanding Microvascular Dysplasia in Dogs
Hepatic microvascular dysplasia (MVD), also known as portal vein hypoplasia, is a congenital or inherited liver condition primarily seen in small-breed dogs. It involves underdeveloped or absent microscopic portal veins within the liver, leading to reduced blood flow and nutrient processing. Despite sounding alarming, many dogs with MVD live full, healthy lives.
What Is Microvascular Dysplasia?
MVD is characterized by a disruption in normal liver blood flow due to the abnormal formation of tiny portals in the liver. Without these healthy vessels, blood bypasses areas of the liver, reducing its ability to detoxify, metabolize, and synthesize vital proteins.
Breeds Commonly Affected
- Yorkshire Terriers
- Cairn Terriers
- Maltese
- Miniature Poodles
- Shih Tzus
- Lhasa Apsos
- Cocker Spaniels
- West Highland White Terriers
- Dachshunds
- Bichon Frises
While more common in small breeds, occasional cases are seen in large dogs and cats.
Symptoms and Clinical Signs
Symptoms vary widely, with many dogs being asymptomatic. Others may show:
- Stunted growth or weight gain
- Lethargy or dullness
- Vomiting and diarrhea
- Pica (eating non-food items)
- Increased urination or thirst
- Blood in urine or straining
- Neurological signs like ataxia, seizures, or behavioral changes (in severe cases)
Severity ranges from imperceptible to debilitating, particularly if hepatic encephalopathy develops.
Diagnosis
Early evaluation typically involves blood and urine analyses, focusing on:
- Bile acid test: Mild to moderate postprandial elevation
- Low protein or albumin levels
- Microscopic changes on liver biopsy
- Imaging like ultrasound, CT, or nuclear scintigraphy to rule out macroscopic shunts
Definitive diagnosis relies on histopathological examination of liver tissue, with multiple samples needed for accuracy.
Prognosis and Life Expectancy
Most dogs with MVD live normal lifespans. Studies and clinical experience show that the majority of affected dogs are either asymptomatic or exhibit only mild signs, manageable through medical therapy and dietary regulation. The condition is generally nonprogressive, especially when properly monitored.
With appropriate care, even dogs showing symptoms due to MVD can experience excellent quality of life. For those with concurrent portosystemic shunts (PSS), surgical intervention might improve their status, but MVD itself is not surgically correctable.
Management and Treatment
Treatment is medical and focuses on reducing symptoms and optimizing liver function.
- Protein-restricted diets using dairy or soy sources
- Prescription liver diets rich in micronutrients
- Lactulose to minimize ammonia absorption
- Short-term metronidazole for intestinal flora modulation
- Hepatic supplements: SAMe, Vitamin E, milk thistle (silymarin), and ursodeoxycholic acid
- Optional use of probiotics or yogurt
These treatments help alleviate symptoms of encephalopathy and preserve normal liver function.
Monitoring and Follow-Up
Regular veterinary checkups, especially monitoring for:
- Liver enzymes
- Protein and ammonia levels
- New or worsening clinical signs
Routine bile acid testing is not always necessary unless indicated by a change in condition.
Genetic Considerations
Because MVD has a suspected polygenic inheritance, breeding of affected dogs is discouraged. Even asymptomatic carriers, with normal test results, may pass the disorder to their offspring.
Summary
Hepatic microvascular dysplasia, albeit a congenital liver issue, doesn't necessarily limit a dog's lifespan. While some dogs may experience mild to moderate symptoms, most live full, healthy lives with no significant disease progression. Proper diagnosis, appropriate dietary and medical management, and vigilant monitoring are key for ensuring a high quality of life in affected pets.
