How do you manage congenital portosystemic shunts? - DVM
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How do you manage congenital portosystemic shunts?


Image 5.
The CBC findings may include microcytic, normochromic erythrocytes and/or a mild nonregenerative anemia. Serum chemistry profiles may reveal mild increases in the serum activity of ALT, AST and ALP. In most animals with congenital PSS, the total bilirubin values are normal.

Albumin values may be mildly decreased. Coagulation profiles including prothrombin time, activated partial thromboplastin time and fibrinogen are usually normal. Serum glucose values may be normal, mildly reduced or markedly hypoglycemic. The BUN concentration may be low or in the low normal range in any young animal with hepatic dysfunction. The most reliable and consistent blood test for the detection of liver dysfunction in puppies with congenital portosystemic shunt is the 12- to 24-hour fasted and two-hour postprandial serum bile acid concentrations.

Image 6.
Diagnostic imaging Diagnostic imaging of a puppy with abnormal serum bile acid values is to determine if a suspected congenital portosystemic shunt is present. Animals with congenital portosystemic shunt frequently have reduced hepatic size, i.e., rounded contour of the caudal edge of the liver and cranial displacement of the stomach radiographically.

In addition, these animals may have opaque ammonium biurate calculi. Ultrasonographic findings in puppies with congenital portosystemic shunt include small liver, reduced visibility of intrahepatic portal vasculature, and anomalous blood vessel draining into the caudal vena cava or sometimes into the azygos vein.

Two-dimensional, gray-scale ultrasonography is used to image through a ventral abdominal wall; however, in most large puppies the optimal approach to the portal vein is through a lateral abdominal wall using the right intercostal spaces.

The portal vein is normally visible by ultrasound imaging as ultrasound waves enter the liver at the porta hepatis, ventral to the caudal vena cava. Lobar branches of the portal vein have echogenic walls.

Results of laboratory tests
Congenital intrahepatic portocaval shunts are identified on the basis of their ultrasonographic appearance as left-divisional, central-divisional or right-divisional intrahepatic shunts. Left-divisional intrahepatic shunts have a relatively consistent bent tubular shape and drain into the left hepatic vein. Central-divisional intrahepatic shunts take the form of a foramen between dilated portions of the intrahepatic portal vein and caudal vena cava. Right-divisional intrahepatic shunts appear as large, tortuous vessels that extend far to the right of midline. The morphology of the left-divisional shunts is compatible with patent ductus venosus.

The Irish Wolfhound and Deerhound are predisposed to left-divisional intrahepatic shunts; the Old English Sheepdog and Australian Cattle Dog are predisposed to central-divisional intrahepatic shunts; Labrador and Golden Retrievers are affected by both left- and central-divisional intrahepatic shunts.

Animals with extrahepatic congenital portosystemic shunt typically have an anomalous vessel that drains into the caudal vena cava between the right renal vein and the hepatic veins; because of the dorsal location, this anomalous vessel may be visible only through the right dorsal intercostal spaces.

Congenital portoazygos shunts may also be visualized using the right dorsal intercostal approach, looking for the shunting vessel at the point where it drains into the caudal vena cava is more accurate than trying to examine the various tributaries of the portal vein.

Ancillary serum bile acids results.
Extrahepatic shunts may be difficult to identify ultrasonographically if access to the relevant structures is hindered by the skill level of the person doing the ultrasonographic study, animal's large body size, lack of acoustic windows as a result of reduced hepatic size, or presents with excessive intestinal gas and ascites.

Further details about congenital portosystemic shunts and their management in puppies are found in my textbook - Hoskins JD: The liver and pancreas. In Hoskins JD (ed): Veterinary Pediatrics: Dogs and Cats from Birth to Six Months, Third Edition. Philadelphia, WB Saunders Co., 2001, pp 200-224.


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