Overview of Hepatobiliary Iminodiacetic Acid Scan

Hepatobiliary scintigraphy is a medical test used to check the health and functioning of the biliary system (which helps in digestion and carries waste from liver to intestines) and the liver. This test makes use of a substance known as a ‘radiotracer’ that moves through your liver and biliary system, similar to how bilirubin (a substance produced by the liver) does.

The radiotracer used is called iminodiacetic acid (IDA) or something very similar. It is introduced into the body through the veins, mixes with a protein called albumin, transported to the liver, and then exits into the biliary system. Thus, by tracking the movement of the radiotracer, this test can provide valuable information about your liver and biliary system.

To explain further, in cases of acute cholecystitis (a sudden inflammation of the gallbladder mainly caused by a blocked gallbladder duct), the radiotracer cannot enter the gallbladder and is seen as non-visible during the test. Also, in chronic (or long-term) cholecystitis, the test will show a decreased level of radiotracer in the gallbladder. If the radiotracer is not present in the duodenum (the first part of the small intestine), it could be an indication of biliary atresia (where bile ducts are blocked or not formed) or other obstructions in the biliary system. On the other hand, the presence of the radiotracer outside the biliary system can be an indication of a bile leak.

Another method known as ultrasound is primarily used to initially evaluate gallbladder problems. Ultrasound looks for signs like gallbladder wall thickening, cystic duct widening, and fluid around the gallbladder which indicate suspected acute cholecystitis. However, these signs are secondary and take time to develop. On the other hand, the HIDA scan used in hepatobiliary scintigraphy can directly and promptly detect obstruction of the gallbladder duct.

However, ultrasound still holds the primary place for initial checks mainly because it’s easily available, quick, convenient, doesn’t involve radiation exposure and can suggest other possible diagnoses.

Anatomy and Physiology of Hepatobiliary Iminodiacetic Acid Scan

The biliary system is a group of tubes within and outside the liver. The liver produces a fluid called bile, which enters tiny tubes within the liver known as intrahepatic ducts. These ducts combine to create the left and right hepatic ducts. These, in turn, join together to create the common hepatic duct.

This common hepatic duct then merges with a duct coming from the gallbladder, known as the cystic duct. This merging forms the common bile duct. This duct continues to join with the pancreatic duct, which enters the second part of the small intestine through a place called the ampulla of Vater, or hepato-biliary ampulla.

Surrounding the ampulla of Vater is a ring of muscle known as the sphincter of Oddi. This muscle works like a gate that opens and closes the ampulla, which controls the flow of bile and other digestive juices into the small intestine.

Why do People Need Hepatobiliary Iminodiacetic Acid Scan

A HIDA scan is a type of medical test that looks at how well different parts of your liver and gallbladder are working. It helps doctors understand how well your liver cells are doing their job, if your gallbladder is releasing bile properly, and whether the tubes in your liver that carry bile are unblocked and intact.

A HIDA scan can help diagnose several different conditions, including:

  • Acute cholecystitis: a sudden inflammation of the gallbladder.
  • Chronic cholecystitis: long-term inflammation of the gallbladder.
  • Sphincter of Oddi dysfunction: when the muscle that controls the flow of bile and pancreatic juice to your intestine doesn’t work properly.
  • Biliary atresia: a rare disease in newborns where the bile ducts are blocked or absent.
  • Biliary leak: when bile leaks out of the gallbladder into the rest of the body.
  • Biliary stent patency: checks if a tube placed into the bile duct to keep it open is working properly.

Most cases of acute cholecystitis are caused by gallstones blocking the gallbladder. This causes over 90% of all cases. The remaining cases are caused by a condition called biliary stasis, which affects very old or young people, critically ill patients, and people receiving nutrition through an IV.

Biliary atresia is a critical condition in newborns that causes jaundice. If not treated within the first two to three months of life, it can lead to permanent liver damage. The child might need a liver transplant eventually. A HIDA scan can effectively rule out biliary atresia if a special radioactive tracer is seen in the intestine 24 hours after the scan. However, if the tracer isn’t seen, it doesn’t confirm the baby has biliary atresia, as other conditions can look the same on a scan.

Doctors can also use a HIDA scan to see if there is a leak in the bile ducts after surgery, an injury, or a liver transplant. The scan can detect if the tracer moves out of the bile ducts, which means there is a leak. Finally, a HIDA scan can check if a tube called a stent, which is placed in the bile duct to keep it open, is working properly.

When a Person Should Avoid Hepatobiliary Iminodiacetic Acid Scan

When having a special medical test called a radiotracer scan, there are circumstances where a person might not be able to have the test. These circumstances are divided into absolute (must not) and relative (preferably not) situations. Fortunately, absolute cases where a person’s body reacts dangerously to the substances used in the scan are quite rare.

On the other hand, there are various relative situations which are primarily related to medicine a person is taking, that can disrupt the normal function of the bile system in the body. This could potentially interfere with the scan. For example, pain-killers, specifically opiates, need to be stopped at least 6 hours before the scan. This is because they can cause what appears to be a blockage in a valve of the bile system called the sphincter of Oddi. Moreover, certain conditions such as a child having increased pressure in the brain or a person having difficulty breathing, can make the administration of morphine, a type of opiate, completely unadvisable. If someone has a known dangerous allergic reaction, known as anaphylaxis, to morphine and the scan is to check for acute cholecystitis (a condition involving inflammation of the gallbladder), it is recommended to delay the imaging to 4 hours time.

But it’s not just opiates that can be problematic. Other medicines that can interfere with the ability of the gallbladder to contract, a required process for the accurate results of the scan, also require an examination of their benefit versus the potential risk of changing or stopping them before the scan. These include atropine, benzodiazepines, alcohol (ethanol), indomethacin, nicotine, nifedipine, birth control pills (oral contraceptives), octreotide, and theophylline.

Template diseases can also have an impact. Similarly, medical conditions that decrease gallbladder contraction, including achalasia, celiac disease, Crohn’s disease, diabetes mellitus, irritable bowel syndrome, pancreatic insufficiency, pregnancy, and sickle-cell disease, can also affect the outcome of the scan.

Equipment used for Hepatobiliary Iminodiacetic Acid Scan

This procedure needs a wide-view gamma camera and a tool called a low-energy all-purpose collimator. A gamma camera is a device that detects gamma rays and helps your doctor see the inside of your body. A collimator is an instrument that narrows a beam of particles or waves. In this case, the collimator is used to guide the gamma rays in the right direction.

Who is needed to perform Hepatobiliary Iminodiacetic Acid Scan?

Based on guidelines from the Society of Nuclear Medicine, certain types of professionals are required in order to successfully conduct a nuclear imaging study. This process includes adjusting the equipment correctly, giving patients medications which light up on scans, and making the correct judgments based on those scans.

The team should include a doctor who has specialized certification in either nuclear medicine or nuclear radiology. This specialist is trained to understand and interpret the images produced by nuclear scans.

A medical physicist is also part of this team. They need to be certified in a particular area of focus by either the American Board of Science in Nuclear Medicine or the American Board of Radiology. The physicist’s role is to ensure the equipment is calibrated correctly and operates safely.

Finally, a nuclear technologist is needed. They should have certification in Nuclear Medicine from the Nuclear Medicine Technology Certification Board. This role helps to administer the radiopharmaceuticals, which are the special medicines that make certain body parts visible on the scans.

All three of these professionals work together to ensure a safe, effective, and accurate nuclear imaging study.

Preparing for Hepatobiliary Iminodiacetic Acid Scan

Patients’ preparation for certain tests may vary depending on the health issue that doctors are trying to investigate. This is specifically true when it comes to conditions like cholecystitis (inflammation of the gallbladder) and biliary atresia (a liver condition in infants that affects the bile ducts).

If you’re being checked for cholecystitis, you will be asked to not eat anything for 3 to 4 hours before a certain substance (known as an IDA injection) is injected into your body. Eating fat can trigger the release of a hormone called cholecystokinin, which makes the gallbladder shrink and may lead to an incorrect result. Not eating allows food to pass through your system and the gallbladder to relax.

However, if you don’t eat anything for more than 24 hours, the gallbladder may absorb water from bile (a digestive fluid), which then becomes thick and may prevent the tracer from entering it. This could result in a false positive, where the gallbladder is not visible in the scan. To avoid this, a medicine called sincalide should be given to you prior to the scan. This medicine helps the gallbladder to shrink and empty out. Doctors usually give it into a vein, and the dosage depends on your weight. The tracer should be injected at least 30 minutes after administering sincalide, so that the gallbladder has time to relax.

For the assessment of biliary atresia, a different procedure is used, which involves the use of a medicine called phenobarbital. This medicine is useful in distinguishing between newborn jaundice and biliary atresia, as it activates liver enzymes, aids in the processing of bilirubin (a yellowish substance produced by the liver) and helps it to be excreted from the body. Doctors recommend a dose of this medicine for five days before the scan.

How is Hepatobiliary Iminodiacetic Acid Scan performed

When you are undergoing a particular medical examination, the first hour tends to follow a standard process, regardless of the reason for the test. You would typically be lying on your back on a table, while a harmless substance known as Tc-99 is quickly put into your bloodstream. A computer starts taking images during this time. For the first minute, 60 pictures are taken at one-second intervals, and then for the next hour, a picture is taken every single minute. Then, pictures are taken from different angles to help doctors get a clear idea of what’s happening inside your body, such as to separate the signal from the shared bile duct, gallbladder, and upper part of the intestines.

After the first hour, the method used may change based on what the doctor suspects might be wrong. Some conditions would require the doctor to see signals outside of the biliary system (the passages through which bile, a fluid that helps digestion, flows), the specific layout of the biliary system, certain areas of lower uptake (rate at which tissue uses a substance), and/or passage of signals into the upper part of the intestines. Other conditions like sudden and severe, or longstanding inflammation of the gallbladder, and obstruction in the bile ducts would evaluate whether bile ducts are unobstructed.

In cases of sudden, severe inflammation of the gallbladder (acute cholecystitis), if the gallbladder is not visible on the images at one hour, it could be because of several reasons. Late images (at 3 to 4 hours), though not ideal as quick diagnosis and treatment are generally preferred in these situations, can help verify the possibility of acute cholecystitis. Nowadays, if the gallbladder is not visible during the first hour, a mild painkiller called morphine is usually given, which causes the muscular valve regulating the flow of bile to contract, closing the duct that bile flows through, diverting incoming bile to the gallbladder. In normal individuals, filling of the gallbladder is visible between 5 to 10 minutes after giving morphine and would be complete by 30 minutes. The entire procedure can be completed in 90 minutes. If the gallbladder still isn’t visible, it confirms the presence of acute cholecystitis.

In the case of longstanding inflammation of the gallbladder (chronic cholecystitis), inflammation typically comes from a decreased ejection fraction which means less fluid is being ejected from an organ than it should. A substance called sincalide is given, and it generally takes around 60 minutes to capture the images. This ejection fraction is then calculated, and while there is no established limit for this value, historically it’s around 40 percent.

Because this procedure is reflective of liver function, if there is reduced liver function, late images could be required, sometimes going past the standard limit to 24 hours. Imaging beyond that point is discouraged due to breakdown of the radiotracer (Tc-99).

Possible Complications of Hepatobiliary Iminodiacetic Acid Scan

In a usual HIDA scan, which is a type of imaging test used to examine the liver, gallbladder, bile ducts, and small intestine, a person is exposed to a small amount of radiation, about 3-4 mSv. This is roughly the same amount of radiation you would naturally be exposed to in a year just by going about your ordinary activities. To put this in perspective, a chest x-ray, another type of imaging test, exposes you to a much smaller 0.001 mSv dose of radiation. On the other hand, a head CT scan, which is a more detailed imaging test that uses x-rays, might require exposure to about 1-5 mSv of radiation.

What Else Should I Know About Hepatobiliary Iminodiacetic Acid Scan?

A hepatobiliary IDA or HIDA scan is a test that helps doctors to examine the health of your liver and bile ducts, an important part of your digestive system. The HIDA scan uses a special dye to make these areas visible on an imaging machine. This dye traces the same path that bilirubin, a waste product of red blood cells that the liver helps to break down, follows in your body. This allows doctors to spot any issues such as blockages in the bile ducts.

This test can also, albeit less accurately, provide insight into the structure of your bile ducts and how well your liver is functioning.

Frequently asked questions

1. What specific conditions or issues is the Hepatobiliary Iminodiacetic Acid Scan able to diagnose or detect? 2. How does the Hepatobiliary Iminodiacetic Acid Scan differ from other imaging tests, such as ultrasound, in terms of accuracy and effectiveness? 3. Are there any medications or medical conditions that could interfere with the results of the scan? If so, what steps should I take to prepare for the scan? 4. What is the typical duration of the scan, and what can I expect during the procedure? 5. What are the potential risks or side effects associated with the Hepatobiliary Iminodiacetic Acid Scan, particularly in terms of radiation exposure?

A Hepatobiliary Iminodiacetic Acid (HIDA) scan is a medical procedure that involves injecting a radioactive substance into the body to examine the function of the biliary system. The scan can help diagnose conditions such as gallbladder disease, bile duct obstruction, or liver problems. The scan is generally safe, but there may be some risks involved, such as an allergic reaction to the radioactive substance or discomfort during the injection. It is important to discuss any concerns or potential side effects with a healthcare professional before undergoing the procedure.

You may need a Hepatobiliary Iminodiacetic Acid (HIDA) scan if you have certain medical conditions or are taking certain medications that can affect the function of your bile system. This scan is used to evaluate the function of your gallbladder and bile ducts. It can help diagnose conditions such as acute cholecystitis (inflammation of the gallbladder), gallstones, and bile duct obstructions. By assessing the movement of a radioactive substance called HIDA through your bile system, the scan can provide valuable information about the functioning of your gallbladder and the flow of bile.

A person should not get a Hepatobiliary Iminodiacetic Acid Scan if they are taking certain medications that can interfere with the function of the gallbladder or if they have certain medical conditions that decrease gallbladder contraction. Additionally, if a person has a known dangerous allergic reaction to morphine and the scan is to check for acute cholecystitis, it is recommended to delay the imaging.

There is no specific information provided in the text about the recovery time for a Hepatobiliary Iminodiacetic Acid (HIDA) scan.

To prepare for a Hepatobiliary Iminodiacetic Acid (HIDA) scan, you should not eat anything for 3 to 4 hours before the scan. It is important to avoid eating fat, as it can cause the gallbladder to shrink and potentially lead to an incorrect result. Depending on the specific circumstances, you may also be given medications such as sincalide or phenobarbital prior to the scan to help relax the gallbladder and ensure accurate results.

The text does not provide information about the complications of Hepatobiliary Iminodiacetic Acid Scan.

Symptoms that would require a Hepatobiliary Iminodiacetic Acid Scan include sudden or long-term inflammation of the gallbladder (acute or chronic cholecystitis), dysfunction of the muscle that controls the flow of bile (Sphincter of Oddi dysfunction), blockage or absence of bile ducts in newborns (biliary atresia), bile leakage from the gallbladder, and the need to check the functionality of a tube placed in the bile duct (biliary stent patency).

Based on the provided information, there is no specific mention of the safety of a Hepatobiliary Iminodiacetic Acid (HIDA) scan during pregnancy. However, it is generally recommended to avoid unnecessary medical procedures and radiation exposure during pregnancy, especially during the first trimester when the fetus is most vulnerable to potential risks. If a HIDA scan is deemed necessary during pregnancy, the potential benefits and risks should be carefully evaluated by the healthcare provider. They will consider the specific circumstances and potential impact on the mother and fetus. Alternative imaging techniques that do not involve radiation, such as ultrasound, may be preferred in pregnant women. It is important to consult with a healthcare provider to discuss the specific situation and determine the best course of action.

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