Angiography is occasionally needed to evaluate the blood vessels of the liver. If a clot in the vessels leading to or leaving from the liver is suspected, specific x-rays showing these blood vessels may be needed. A dye can be injected into the artery supplying the liver by putting a long tube or catheter into the artery in the groin and threading it up into the liver. Follow up images of these pictures or arteriograms can demonstrate the vein leading to the liver (the portal vein). Other techniques can be used to put dye into the portal vein directly. If an abnormality of the hepatic vein, the vein that leaves the liver, is suspected, dye can be injected through a vein in the neck into the inferior vena cava, a large vessel which takes blood back to the heart. Through this vessel, the hepatic vein can be reached and pressures can be measured. This test is performed by an interventional radiologist, with the patient under sedation or anesthesia.
CT Scan or CAT Scan or Computerized Tomography
CT Scan or CAT Scan or Computerized Tomography can be used to get a more accurate picture of the liver. This x-ray is usually done with the patient fasted for several hours. The patient is often asked to drink dye, and dye is injected into the veins as well. This x-ray can give an accurate picture of the liver and of the blood vessels that lead to and flow from it, as well as the bile ducts. This study may be used to demonstrate gallstones, tumors, fatty changes in the liver, etc.
Hepatobiliary Scan is a nuclear medicine study (sometimes also called a DISIDA scan or HIDA scan) that can be used to assess bile flow. In this test a harmless radioactive substance is injected into the child's vein. This substance is accumulated in the liver and then secreted into the bile which accumulates in the gallbladder. When the gallbladder squeezes, the dye should go through the bile ducts and appear in the intestine. If liver function is poor, the dye may not accumulate well in the liver. If bile flow is obstructed (if the bile ducts did not form as in biliary atresia, or if the bile ducts are blocked by a stone when the patient has gallstones) then bile flow from the liver to the intestine is not seen in this study. Sometimes, to make sure that the radiologist has given the patient every chance to demonstrate flow, a follow-up x-ray is done at 24 hours. It is important to know that not every child who has "no excretion" on the hepatobiliary scan actually has a blockage to bile ducts. Poor liver function can make the liver appear as if bile flow is blocked.
MRCP or Magnetic Resonance Cholangiopancreatography
MRCP or Magnetic Resonance Cholangiopancreatography may be used to get a better picture of the bile ducts. In this new technology, an MRI scan of the abdomen is done with the patient fasted and lying very still (often sedated). Special computer techniques allow for pictures of the bile ducts and pancreatic ducts to be taken from these images. These pictures may be used to look for blockage or narrowing of the ducts that leave the liver.
Ultrasound is carried out in the x-ray department on a child who has not eaten in several hours. A lubricant jelly is placed on the child's abdomen and a smooth wand that looks much like a microphone is touched to the patient's skin and moved about. This test is not painful. A black and white picture representing sound waves going through the liver is created. This test can look at the tissue of the liver to see if it is too fatty, too dense or irregular. It may identify a spot such as an abscess, cyst or tumor. This test can also evaluate bile ducts to see if the bile ducts are swollen or dilated (this might suggest a blockage downstream). The ultrasound may also show a stone that is stuck in a bile duct. Ultrasound can also be done with a test called Doppler which looks at the flow of blood in the vessels of the liver. Dopplers may be able to identify blockages of arteries or veins that go to the liver or veins that leave the liver. Ultrasound can also assess for the presence or absence of the gallbladder and can look at other organs in the abdomen such as the pancreas, kidneys, etc.