Hepatic Microvascular Dysplasia
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- Small intrahepatic portal vessels and portal endothelial hyperplasia which allows abnormal communication between portal and systemic circulation.
- Can develop as a separate entity or in conjunction with a portosystemic shunt.
- Can cause c/s similar to those of PSS.
- Vomiting, diarrhoea, urinary tract changes associated with ammonium biurate urolithiasis, stunted growth, prolonged recovery from anesthesia.
- Average age of presentation =3yrs.
- Mainly small dogs, esp. Yorkies
- Females>males
Histology
- Arteriolarization of central veins
- smooth muscle proliferation (segmental) within the walls of central veins
- random distribution of small calibre vessels
- endothelial hyperplasia within portal triads
- dilation of periacinar vascular spaces.
- May also see decreased diameter of intrahepatic veins.
- Can’t be accurately distinguished from PSS alone.
- Seen in older dogs than PSS
- Higher MCV, serum postprandial bile acid concentrations, serum albumin and cholesterol concentrations when PSS and HMD together, compared to HMD alone.