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Microvascular Dysplasia, Hepatic 655

those situations, removal of the nidus (e.g., less zoonotic risk, but rare human infections (e.g., protective outerwear, handwashing) is
have been reported.
important for any patient.
explantation) is the key. • Screening of veterinary personnel for MRS • Animals that are known to be infected or
VetBooks.ir PROGNOSIS & OUTCOME Prevention colonized should be handled with enhanced Diseases and Disorders
colonization is rarely, if ever, indicated.
precautions. This can include protective
Prognosis for MRS infections should be no dif-
of movement in the clinic, and isolation
ferent than for infections caused by susceptible • Routine cleaning and disinfection kill MRS outerwear (e.g., gown, gloves), restriction
microorganisms if there is a prompt diagnosis when performed properly. if possible. Isolation is preferred during
and institution of appropriate treatment. • Quarantine of exam rooms for 24-48 hours hospitalization when possible.
after confirmation of MRS infection in a • MRS are killed by routine disinfectants if
PEARLS & CONSIDERATIONS patient is not beneficial because if staphylococci used properly.
were missed during cleaning and disinfection,
Comments they can be expected to persist for 1-2 weeks Client Education
• Main clinical issues for MRS infections: or until proper disinfection is completed. Client education helps ensure proper man-
○ Difficulty in treating MRS infections • A focus on good routine infection control agement and also can prevent an excessive
because of limited drug options and practices is recommended because MRS response based on fear of MRSA. Providing
options that may be undesirable status is unknown initially for carriers and reference materials from reputable sources (e.g.,
○ Potential for more severe disease if culture animals with active infections. http://www.wormsandgermsblog.com, http://
is not performed promptly because empiri- ○ Routine cleaning and disinfection www.thebellamossfoundation.com) can help
cal treatment will likely fail ○ Avoid contact between MRS cases and allay fears and improve patient care.
○ Zoonotic risk (mainly MRSA) and other animals. For example, any animal
transmission of MRS to other high-risk with known MRS infection or all animals SUGGESTED READING
animals, especially surgical patients, with pyoderma should bypass the waiting Morris DO, et al: Recommendations for approaches
because MRSP surgical site infections room to avoid lying beside another patient to methicillin-resistant staphylococcal infections of
can be a major concern being admitted for orthopedic surgery or small animals: diagnosis, therapeutic considerations
• MRS are not inherently more virulent than receiving immunosuppressive treatment. and preventative measures. Clinical Consensus
susceptible staphylococci, and the prognosis ○ Good attention to hygiene, especially hand Guidelines of the World Association for Veterinary
for MRS infections is usually good. The key hygiene Dermatology. Vet Dermatol 28:304-e69, 2017.
is early recognition by culture to ensure that AUTHOR: J. Scott Weese, DVM, DVSc, DACVIM
proper treatment is initiated and the risk of Technician Tips EDITOR: Manon Paradis, DMV, MVSc, DACVD
transmission is minimized. • Care must be taken to reduce the risk of
• MRSA is a public health concern, and transmission of MRS between patients and
animal-human transmission can occur. Good from patients to personnel.
general infection control practices should • Because healthy animals may carry MRS, use
greatly minimize the risk. MRSP is of much of good general infection control practices

Microvascular Dysplasia, Hepatic Client Education
Sheet

BASIC INFORMATION hypoperfusion, microvascular portal dysplasia, ASSOCIATED DISORDERS
portal venous atresia • Concurrent PSVA and HMD offers an
Definition explanation for the frustrating persistence
Hepatic microvascular dysplasia (HMD) Epidemiology of symptoms and/or abnormal test values
involves a defect at the terminal branching SPECIES, AGE, SEX related to shunting despite apparent adequate
of portal venules, with variable severity. • More common in small, purebred dogs but surgical attenuation of PSVA.
This causes intrahepatic shunting of portal may be seen in any breed or outcross • HMD can be concurrent with congenital
blood to the systemic venous return, causing • Less common or rare in cats PSVA, primary portal vein hypoplasia, portal
intrahepatic portal venous hypoperfusion. • A congenital disease that may be diagnosed vein atresia, hepatic arteriovenous fistula, and
Additional secondary microscopic alterations in older or younger patients based on sever- rare portal venous agenesis. Pursue advanced
of the hepatic parenchyma compound the ity of clinical signs or results of screening diagnostic imaging and liver biopsy during
severity of shunting, with hepatic dysfunction tests all PSVA surgeries.
proportional to the degree of portosystemic • HMD has been reported concurrent with
shunting. HMD can occur alone or be GENETICS, BREED PREDISPOSITION ductular plate malformations.
found in combination with macrovascular Predominantly toy breeds such as Yorkshire, Clinical Presentation
disorders such as primary portal vein hypo- Cairn, and Maltese terriers; also reported in
plasia or portal systemic vascular anomalies other pure- and mixed-breed dogs, including DISEASE FORMS/SUBTYPES
(PSVAs) such as portal systemic shunt pugs, dachsunds, miniature poodles, Lhasa apso, • Most animals with HMD have minimal or
(PSS). shih tzu, cocker spaniel, Havanese, and West no clinical signs.
Highland white terriers • Rarely, signs suggesting PSVA or chronic
Synonyms Pattern of inheritance is thought to be tied hepatopathy occur, or there may be progres-
HMVD, microvascular dysplasia (MVD), to that of PSVA (p. 814) as an autosomal sion to noncirrhotic portal hypertension.
hepatoportal microvascular dysplasia, a form of dominant mode, likely polygenic, and with • Liver dysfunction may be discovered
portal venous hypoplasia (PVH) or portal vein simple to complex expression. unexpectedly during assessment for other

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