PRESENTATION
5 month intact male Bichon Frise presented with intermittent vomiting for 4 months.
HISTORY
Chemistry profile revealed hypoproteinemia and reduced BUN with normal liver enzyme values. Bile acids were abnormally elevated on both pre and postprandial
samples. Nuclear scintigraphy was strongly suggestive of a portosystemic shunt.
TREATMENT
Exploratory laparotomy did not reveal a portosystemic shunt vessel in the typical region of the epiploic foramen. The portal vein appeared well-developed. Several small vessels were identified leading to the left renal vein.
Portal pressure was within the normal range of 8-13 cm H20 and did not change when the suspected shunt vessels were occluded. Mesenteric portography (shown below) revealed well-developed intrahepatic portal circulation and apparent multiple small portocaval shunts originating from the portal and cranial mesenteric vasculature and traversing toward the caudal vena cava in the region of the kidneys. A liver biopsy was obtained for histopathologic analysis. Medical management with lactulose, metoclopramide, cimetidine and Hill's I/D diet
was continued postoperatively.
OUTCOME
Histopathologic analysis of the liver biopsy revealed lobular and vascular atrophy. A final diagnosis of small multiple extrahepatic shunts was made, suspected to have occurred secondary to Hepatic Microvascular Dysplasia (HMD). Three years later, the intermittent vomiting remained infrequent and the patient had an excellent quality of life at 6 years of age despite the hepatic abnormality.
DISCUSSION
Multiple extrahepatic shunts generally develop in response to underlying liver disease causing increased portal pressure. Ligation of the multiple vessels is not in the patient's best interest unless the underlying liver condition can be resolved, since new shunt vessels will simply form if portal pressure elevation persists. This patient did not have increased portal pressure intraoperatively, however HMD is
suspected to cause transient portal pressure increases. Medical management is the only treatment option. Long term survival with HMD is not reported since its diagnosis is relatively recent. HMD can occur alone or in combination with an extrahepatic shunt. The clinical signs associated with HMD are similar to portosystemic shunts but less marked. Blood work often reveals abnormalities only in bile acids and liver enzymes. Portogram can be normal and the only method of definitive diagnosis is biopsy.
