HIDA - A Novel Diagnostic Method

Introduction:

The digestive system comprises various vital organs such as the stomach, small and large intestines, liver, and gallbladder. Along with these organs, certain accessory ducts and organ secretions are also crucial for efficiently carrying out the digestive process. Every macro and micronutrient must be digested and absorbed in the body for maximum utilization. Each organ is adept at carrying out specialized functions that contribute to the digestion and metabolism process. For example, the liver secretes bile which helps the body to break down fat. In addition, the bile is transported to the gallbladder for storage and future use. Hence liver and gallbladder are vital organs in fat metabolism.

Conditions affecting the liver and gallbladder would affect various bodily metabolic functions, resulting in severe complications and even fatalities. Though abdominal ultrasound may prove helpful in assessing the morphologic and structural abnormalities of the liver and gallbladder, it is not efficient to understand the functioning of these organs. Hence a functional scan is preferred to evaluate the hepatobiliary organs, particularly the gallbladder.

What Is a HIDA Scan?

HIDA scan or hepatobiliary iminodiacetic acid scan is also known as cholescintigraphy or hepatobiliary scintigraphy. It is a diagnostic nuclear imaging test used to assess and evaluate the liver, gallbladder, and bile duct. It can also help assess these organs' functioning and determine the rate at which the bile is secreted from the gallbladder. This procedure uses radioactive material which is injected into the veins. This tracer travels through the blood and distributes it throughout the hepatobiliary organs. A specialized gamma camera can help track the tracer's flow and localization.

Where Is the HIDA Scan Indicated?

A HIDA scan is indicated in the following conditions:

• Unexplained and severe abdominal pain, particularly on the right side of the abdomen, could be due to an inflammatory disease of the gallbladder.

• Severe jaundice in a newborn could be a sign of biliary atresia, which requires immediate medical attention.

• To assess the rate and flow of bile from the liver and gallbladder.

• It can be used to evaluate the functioning of the liver, gallbladder, small intestines, and bile duct.

It can be used to diagnose the following conditions:

• Gallbladder inflammation.

• Gallstones.

• Congenital abnormalities.

• To assess the liver transplant and its functioning postoperatively.

• To evaluate post-surgical complications after any surgery.

• Blocked bile ducts.

• Bile leakage.

• Cysts and tumors of the hepatobiliary organs.

• Following a biliary stent placement.

What Are the Instructions to Be Followed by the Patients Before a HIDA Scan?

• Patients are requested to fast for four to six hours before the procedure. However, clear fluids may be allowed.

• Patients on prescription medicines like pain relievers, vitamin supplements, or any other medication should inform the doctor. These medicines may have to be stopped before the scan as they may interfere with the biliary functions.

• Patients should wear loose, comfortable clothes.

• They should remove their jewelry, valuables, and other metallic accessories at home. In addition, patients are advised to remove their eyeglasses, removable dentures, and hearing aids before the procedure.

• Pregnant and breastfeeding ladies should inform the doctor before the procedure as this procedure is not recommended for them.

• Patients with a history of allergic reactions to contrast materials, medicines, or latex are also advised to inform the doctor.

How Is the HIDA Scan Done?

• HIDA scan is a relatively simple procedure. It is carried out on an outpatient basis, and the entire procedure may take one to four hours.

• There is no requirement for anesthesia; however, pediatric patients and those with neurological impairment may find it difficult to remain still and hence may require a sedative.

• Patients will be given a hospital gown to wear and will be assisted to a scanning room.

• They will be made to lie on an examination table.

• An intravenous line will be accessed for administering the radioactive tracer.

• While injecting the tracer, the patient may experience a burning or a cold sensation.

• The abdomen portion will be exposed, and a gamma scanner will be placed over the belly region in close contact.

• The camera would move back and forth and rotate while taking images. The patient is requested to remain still as the slightest movement will cause blurring of the images.

• Patients may be asked to turn around for better visibility and access.

• Once the desired images are taken, the patient may be administered Morphine or similar drugs to relax and empty the gallbladder. This would help gain more explicit images.

What Are the Instructions After the Procedure?

There are no special restrictions after the procedure. Patients can resume their regular activities and diet. They are also advised to drink plenty of water so that the radioactive material can be expelled from the body via urine or stool. Lactating mothers should avoid breastfeeding their kids for the next 24 hours till the radioactive material is expelled from the body. They can pre-pump and store the breast milk before the procedure.

How Are the Results Interpreted?

The results are given below:

• Normal: Free movement of the radiotracer from the liver to the gallbladder and small intestine suggests no abnormality.

• Slow or Impaired Movement: Suggestive obstruction of poor liver functioning.

• Nil Radiotracer in the Gallbladder: Suggestive of acute gallbladder inflammation.

• Abnormally Reduced Gallbladder Ejection Fraction: This indicates reduced tracer material exiting the gallbladder after injecting the drug to empty it, suggestive of chronic inflammation.

• Radioactive Tracer Detected in Other Areas: Suggestive of biliary leakage.

What Are the Risks Associated with the Procedure?

The risks associated with the procedure are:

• Allergic reaction to the contrast material used.

• Radiation exposure, though only minimal.

• Bruising at the intravenous site.

Conclusion:

HIDA scan is a novel and advanced diagnostic test to evaluate hepatobiliary organs. Though ultrasound is a handy and most commonly used imaging tool to diagnose gastrointestinal disorders, it is not adept enough to help understand the functioning of these organs. Assessing these organs' functioning and structural conditions is crucial for better and more precise diagnosis. HIDA scan is significantly superior to conventional ultrasound and is considered the gold standard for diagnosing gallbladder disorders.