What is a HIDA Scan? Purpose, Procedure & Results

A HIDA scan is a special imaging test that helps doctors see how well your gallbladder and bile ducts are working. Think of it as a detailed movie of your digestive system in action, specifically focusing on how bile flows from your liver through your gallbladder and into your small intestine.

This test uses a small amount of radioactive material that's completely safe and gets eliminated from your body naturally. The scan takes pictures over time to show your doctor exactly what's happening inside, helping them diagnose problems that might be causing your symptoms.

What is a HIDA scan?

A HIDA scan, also called hepatobiliary scintigraphy, is a nuclear medicine test that tracks bile flow through your liver, gallbladder, and bile ducts. The name comes from the radioactive tracer used called hepatobiliary iminodiacetic acid.

During the test, a technologist injects a small amount of radioactive tracer into your arm vein. This tracer travels through your bloodstream to your liver, where it mixes with bile. A special camera then takes pictures as the tracer moves through your bile ducts and gallbladder, showing how well these organs are functioning.

The scan is completely painless and typically takes between one to four hours to complete. You'll lie on a table while the camera moves around you, but you won't feel the radiation or the tracer moving through your body.

Why is a HIDA scan done?

Your doctor orders a HIDA scan when you have symptoms that suggest problems with your gallbladder or bile ducts. This test helps pinpoint exactly what's causing your discomfort and guides treatment decisions.

The most common reason for this scan is to check for gallbladder disease, especially when other tests like ultrasound haven't provided clear answers. Your doctor might suspect cholecystitis, which is inflammation of the gallbladder, or problems with how your gallbladder contracts and empties.

Here are the main conditions a HIDA scan can help diagnose:

• Acute cholecystitis (sudden gallbladder inflammation)
• Chronic cholecystitis (long-term gallbladder inflammation)
• Gallbladder dysfunction or poor gallbladder emptying
• Bile duct obstruction or blockage
• Bile leaks after surgery
• Biliary dyskinesia (gallbladder doesn't contract properly)

Sometimes doctors also use HIDA scans to evaluate less common conditions like sphincter of Oddi dysfunction, where the muscle controlling bile flow doesn't work correctly. The test can also help assess complications after gallbladder or liver surgery.

What is the procedure for a HIDA scan?

The HIDA scan procedure is straightforward and happens in a hospital's nuclear medicine department. You'll work with specially trained technologists who will guide you through each step and answer any questions you have.

First, you'll change into a hospital gown and lie down on a padded table. A technologist will insert a small IV line into your arm, which feels like a quick pinch. Through this IV, they'll inject the radioactive tracer, which takes just a few seconds.

Here's what happens during the scan:

1. You'll lie still on the table while a large camera moves around you
2. The camera takes pictures every few minutes for the first hour
3. If your gallbladder fills with tracer, you might receive a medication called CCK to make it contract
4. Additional pictures are taken to see how well your gallbladder empties
5. The entire process usually takes 1-4 hours depending on how your body responds

During the scan, you can breathe normally and even talk quietly, but you'll need to stay as still as possible. The camera doesn't touch you and makes minimal noise. Most people find the test relaxing, though lying still for extended periods can be uncomfortable.

If your gallbladder doesn't fill with tracer within the first hour, your doctor might give you morphine to help concentrate the tracer. This can extend the test time but provides more accurate results.

How to prepare for your HIDA scan?

Proper preparation ensures your HIDA scan gives the most accurate results possible. Your doctor's office will provide specific instructions, but here are the typical requirements you'll need to follow.

The most important preparation step is fasting for at least four hours before your test. This means no food, drinks (except water), gum, or candy. Fasting helps your gallbladder concentrate bile, making it easier to see during the scan.

Before your appointment, let your medical team know about these important details:

• All medications you're taking, including over-the-counter drugs
• Any allergies you have
• If you're pregnant or breastfeeding
• Recent illnesses or other medical tests
• Previous reactions to contrast materials or medications

You should continue taking your regular medications unless your doctor specifically tells you to stop. However, some medications can affect the test results, so your doctor might ask you to temporarily stop certain drugs like narcotic pain medications.

Wear comfortable, loose-fitting clothes without metal zippers or buttons near your abdomen. You'll likely change into a hospital gownway, but comfortable clothing makes the experience more pleasant.

How to read your HIDA scan results?

Your HIDA scan results show how well bile flows through your liver, gallbladder, and bile ducts. A nuclear medicine specialist called a radiologist will analyze your images and send a detailed report to your doctor.

Normal results show the tracer moving smoothly from your liver into your gallbladder within 30-60 minutes. Your gallbladder should fill completely and then empty at least 35-40% of its contents when stimulated with CCK medication.

Here's what different results typically mean:

• Normal scan: Tracer fills the gallbladder and empties properly, indicating healthy function
• No gallbladder filling: Suggests acute cholecystitis or gallbladder inflammation
• Delayed filling: May indicate chronic cholecystitis or partial blockage
• Poor emptying: Could mean gallbladder dysfunction or biliary dyskinesia
• Tracer doesn't reach intestines: Suggests bile duct obstruction

Your ejection fraction is a key measurement that shows what percentage of bile your gallbladder empties. A normal ejection fraction is typically 35% or higher, though some labs use 40% as their cutoff point.

If your ejection fraction is below normal, it might indicate functional gallbladder disease even if other tests appear normal. However, your doctor will consider all your symptoms and test results together before making treatment recommendations.

What are the risk factors for abnormal HIDA scan results?

Several factors can increase your chances of having an abnormal HIDA scan, though many people with these risk factors never develop gallbladder problems. Understanding these factors helps you and your doctor make informed decisions about your health.

Age and gender play significant roles in gallbladder disease. Women are more likely to develop gallbladder problems, especially during pregnancy or when taking hormone replacement therapy. The risk increases with age, particularly after 40.

These lifestyle and medical factors can increase your risk:

• Rapid weight loss or yo-yo dieting
• High-fat, low-fiber diet
• Obesity or being significantly overweight
• Diabetes or insulin resistance
• Family history of gallbladder disease
• Certain medications like birth control pills
• Inflammatory bowel disease
• Previous abdominal surgery

Some people develop gallbladder problems without any obvious risk factors. Genetics play a role, and certain ethnic groups, including Native Americans and Mexican Americans, have higher rates of gallbladder disease.

Pregnancy is a special consideration because hormonal changes can affect gallbladder function. If you're pregnant and need a HIDA scan, your doctor will carefully weigh the benefits against any potential risks.

What are the possible complications of abnormal HIDA scan results?

While an abnormal HIDA scan itself doesn't cause complications, the underlying gallbladder problems it reveals can lead to serious health issues if left untreated. Understanding these potential complications helps you appreciate why follow-up care is so important.

Acute cholecystitis, shown by a gallbladder that doesn't fill with tracer, can progress to dangerous complications. The gallbladder wall can become severely inflamed, infected, or even rupture, requiring emergency surgery.

Here are the main complications that can develop from untreated gallbladder disease:

• Gallbladder perforation: The gallbladder wall breaks open, spilling infected bile into your abdomen
• Gangrene: Gallbladder tissue dies due to lack of blood supply
• Abscess formation: Pockets of infection develop around the gallbladder
• Bile duct stones: Stones move from the gallbladder and block bile ducts
• Pancreatitis: Inflammation of the pancreas caused by blocked bile ducts
• Cholangitis: Serious infection of the bile ducts

Functional gallbladder disease, where the gallbladder doesn't empty properly, can cause chronic pain and digestive problems. While not immediately life-threatening, it can significantly impact your quality of life and may eventually require surgery.

The good news is that most gallbladder problems can be treated effectively when caught early. Your doctor will work with you to develop a treatment plan that addresses your specific situation and prevents complications.

When should I see a doctor for gallbladder symptoms?

You should contact your doctor if you experience symptoms that might indicate gallbladder problems, especially if they're persistent or getting worse. Early evaluation can prevent complications and help you feel better sooner.

The most common gallbladder symptom is pain in your upper right abdomen, often called biliary colic. This pain typically starts suddenly, lasts 30 minutes to several hours, and may radiate to your back or right shoulder blade.

Here are symptoms that warrant medical attention:

• Severe abdominal pain that doesn't improve with position changes
• Nausea and vomiting, especially with abdominal pain
• Fever along with abdominal pain
• Yellowing of skin or eyes (jaundice)
• Clay-colored stools or dark urine
• Persistent indigestion or bloating after fatty meals
• Pain that wakes you from sleep

Seek immediate medical care if you develop severe abdominal pain with fever, chills, or vomiting. These symptoms could indicate acute cholecystitis or other serious complications that require prompt treatment.

Don't ignore recurring mild symptoms either. Frequent indigestion, bloating, or discomfort after eating fatty foods might indicate functional gallbladder disease that could benefit from early intervention.