Abernethy Malformation

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DEFINITION
Updated 5/30/11

A portosystemic shunt (PSS) also know as an Abernethy malformation or a liver shunt, is a vascular connection effecting the body's circulatory system.

In most people, blood from the stomach, intestines, spleen and pancreas drains into the liver through a large vein called the "portal" vein. With a portosystemic shunt, blood draining from the portal system bypasses ("shunts" past) the liver and directly enters the general circulation. As a result the liver does not get a chance to clean or filter the blood.

A portosystemic shunt can be present at birth (i.e. congenital) or acquired as the result of an underlying liver disease that was not present at birth. This blog discusses a congenital portosystemic shunt.

Dr. Karen Tobias from the University of Tennessee is a liver shunt "guru" in the animal world.

I have included her website for detailed information.

Click on the link below.

What is a Liver Shunt?

Click on Vet Surgery Central below for a great diagram by Dr. Daniel A. Degner.

(This shunt diagram demonstrates blood flow of how a shunt bypasses the liver using the anatomy of a dog but may give you a visual of a shunt.)

Vet Surgery Central Inc. diagram

For a detailed medical description

by Dr. R. Superina and Dr. Morgan

of congenital portosystemic shunt classifications

see the right column of this blog.

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HISTORY

CAPV (Abernethy Malformation) was first reported by John Abernethy in 1793. He was an English anatomist, physiologist, and surgeon.

In 2003, only 31 cases of Abernethy malformation, mostly in children (80%) were detected in the world. Since Abernethy malformation can be without symptoms, the number of undiagnosed cases is not known. Possibly due to the increased recognition of Abernethy malformation the number of diagnosed cases appears to be increasing.

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EXAMS AND TESTS

Ultrasonography (ultrasound or US) with Doppler indications, computed tomography (CT scan) with use of IV contrast indications of chest, abdomen and pelvis, magnetic resonance imaging (MRI) and an venogram (angiogram) are used to diagnose an Abernethy malformation.

Liver enzyme test - An initial step in detecting liver damage is a simple blood test to determine the presence of certain liver enzymes in the blood.

Ammonia blood test – a routine blood test that uses blood that is drawn out of a vein. Ammonia tests can also be performed on arterial blood, but this method is much less frequently used.

Oxygen saturation test - An estimate of your oxygen saturation can be made easily and painlessly with a clip that fits on your finger.

A better test for measuring your oxygen saturation is an arterial blood gas test. For this test, a small sample of blood must be drawn directly out of an artery. Most routine blood tests use blood that is drawn out of a vein, so this test is a little different.

SYMPTOMS RESULTING FROM A SHUNT

hyperammonemia

failure to gain weight

hypoglycemia

elevated liver enzymes

seizure activity

coagulopathy

regenerative liver nodules

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TREATMENT OPTIONS

A test in radiology is performed to temporarily block the shunt to see if a portal vein is present and to monitor pressure as the shunt is closed.

If the portal vein is located, depending on the size and anatomy of the vein. It may be possible to permanately block or close the shunt and redirect flow through the portal vein.

If the results indicate a higher presssure then the doctor is comfortable with, then the process may be done in stages to slowly expand the portal vein.

A liver transplant may be another possible option that may be reviewed with your doctor.

WHAT TO EXPECT BEFORE TREATMENT

The reaction of the liver to an uneven blood supply usually results in focal nodular hyperplasia. This is monitored yearly by checking alpha-fetoprotein levels to check for liver cancer and with a yearly CT scan.

Intelligence may be normal, but some may have a learning disability.

Limiting protein intake is advised in some circumstances.

Lactulose or Xifaxan (Rifaximin) can be used if there are signs of hyperammonemia.

QUESTIONS I HAVE

( My disclaimer because I know I should have one :

I am NOT a medical person,

I am just a mom with a blog.)

Should the following be considered possible symptoms of an Abernethy malformation:

telangiectasias or hemangiomas

difficulty with fine motor skills

ADHD-related to attention and short term memory

low grade hepatic encephalopathy

Could HHT be listed as a possible symptom? (A liver shunt is a large AVM.)

***

When my child is hypoglycemic (low blood sugar) and has medical tests that require fasting, should she be on an IV of D5 (sugar solution) due to hyperammonemia?

Should I filter my child's drinking water since my child's liver cannot? (Would a reverse osmosis system be beneficial?)

Is organic food safer than non-organic food?

PEDIATRIC JOURNAL ARTICLE

Management and classification of type II congenital portosystemic shunts