20 Mar, 2024

Why Do I Need an MRI Scan for Gallstones? Your Guide to MRI Gallstone Diagnosis

What is the gallbladder? 

The gallbladder is a small, pear-shaped muscular organ located at the upper right side of the abdomen, just beneath the liver. It has two (2) primary functions: 1. To store, concentrate, and release bile, a digestive juice produced by the liver. 2. To carry away waste. 

Gall is another name for bile; that’s where the gallbladder gets its name. Bile is a greenish-yellow alkaline fluid consisting of water, bile salts and acids, cholesterol, bilirubin (a yellowish pigment formed from dead or damaged red blood cells), electrolytes, phospholipids, protein, and accumulated waste products.

The gallbladder connects to the liver, pancreas, and small intestine via a system of hollow ducts known as the biliary tree (also known as the biliary tract). 

What are gallstones?

Gallstones (medically known as cholelithiasis) are hardened deposits that develop in the gallbladder from bile. They form when sediments—primarily composed of one or more materials that are overly concentrated and not completely dissolved in bile—collect and crystallise (harden), creating a single large stone or cluster of several smaller stones, which can vary in size. It affects 5.5 million people in the UK, with 50,000 requiring cholecystectomies (surgical removal of the gallbladder) per year.  

Based on their chemical composition, there are three types of gallbladder stones, namely:

  • Cholesterol stones (more than 50 percent cholesterol). 

  • Pigmented stones (< 30 percent cholesterol).

  • Mixed stones (< 20 percent cholesterol).

They often result from having too much cholesterol or bilirubin that can't be dissolved in bile or gallbladder stasis (slowed or inactivity of the gallbladder).

What are the symptoms of gallstones?

Gallstones can start out resembling a tiny grain(s) of sand and then grow into the size of a golf ball. They are not often a problem. In fact, unless they are discovered incidentally during routine checkups or when testing for other health problems, many people carry gallstones throughout life without knowing.

It is when gallstones block the neck of the gallbladder or travel through the biliary tract and get lodged in the bile or pancreatic duct that they can become problematic, causing painful symptoms such as:

  • Sudden, severe pain in the upper right side of the abdomen, particularly after consuming high-fat foods or at nighttime. It can be sharp, dull, cramping, or stabbing. Depending on its frequency and duration, the pain can be called a gallbladder attack or biliary colic.

  • Pain that extends to the lower chest, shoulder blades, or back.

  • Pain that wakes you up from sleep

  • Jaundice (yellowing of the skin and whites of the eyes)

  • Low-grade fever and chills

  • Nausea or vomiting

  • Digestive problems such as gas, bloating, and heartburn

  • Dark-brown and light-coloured stools.

It can also lead to serious problems, including:

  • Pancreatitis (inflammation of the pancreas).

  • Cholecystitis (inflammation of the gallbladder wall).

  • Gallbladder cancer or cholangiocarcinoma (bile duct cancer). Gallstones greater than 2 to 3 cm (about the size of a grape) are associated with high gallbladder cancer risk. 

  • Jaundice.

  • Common bile duct stones (CBDS)

  • Cholangitis (infection followed by inflammation of the bile ducts).

How are gallstones diagnosed?

The diagnosis of gallstone may start with a review of your medical history and a physical examination known as the Murphy sign test. Next, your healthcare provider might order some lab tests, including blood tests that can reveal abnormalities such as jaundice, pancreatitis, infections, and elevated enzyme levels, which can help rule out other suspected conditions and suggest the presence of gallstones. An imaging test, such as a magnetic resonance imaging (MRI) scan, will be necessary for a confirmative diagnosis. 

Now, you may wonder: “Why do I need an MRI scan for gallstones?” 

It’s simple. The MRI diagnostic technology is famed for providing detailed, high-resolution images of the body’s internal structures. 

An MRI scan for gallbladder will detect even the smallest gallstones, assess their composition (i.e., whether they are cholesterol, pigment, or mixed stones), and check for the presence of inflammation or infections. If gallstones are absent, an MRI can visualise the condition causing your painful symptoms, making it an invaluable diagnostic tool for investigating unexplained abdominal pain.

There’s also a special type of MRI scan for gallstones in bile duct called magnetic resonance cholangiopancreatography (MRCP), having a sensitivity and specificity rating of 95% for detecting gallstones in the common bile duct. It can be performed as a standalone test or simultaneously with a standard MRI scan.

The abdominal ultrasound is another highly recommended tool for diagnosing gallstones in the gallbladder, boasting a 90 to 95% accuracy rate. It can’t, however, detect stones in the biliary tract, so a follow-up test—preferably an MRCP or endoscopic ultrasound—may be required. Other recommended diagnostic tests include X-ray and computed tomography (CT) scans.

How do gallstones show up on MRI?

Can you see gallstones on MRI? Yes! There are two basic types of images: T1-weighted and T2-weighted images. T1-weighted MRI enhances the signal of fatty tissue while suppressing the signal of water, whereas T2-weighted MRI enhances the signal of water.

Most gallstones, including cholesterol and pigment stones, manifest as hypointense areas (i.e., appearing as darker spots, compared to bile fluids and surrounding fatty tissues) within both T1 and T2 images. However, most pigment stones may appear hyperintense on T1 images, meaning they look brighter than surrounding tissues. 

What are the benefits and risks of MRI for gallstones?

A gallbladder MRI scan is a highly accurate method for running a thorough diagnosis of gallstones, as well as other related causes of abdominal pain. Since it uses strong magnetic fields and radiofrequency waves to create high-contrast, detailed visuals of organs and ducts, there’s no radiation risk involved compared to an X-ray. 

Abdominal X-rays are limited in sensitivity to gallstones because they can only visualise calcified stones (i.e., stones with a significant amount of calcium carbonates), and only about 10% of stones are calcified. In contrast, an MRI gallbladder scan and the MRCP MRI can detect and distinguish all types of gallstones. The best part is that it is non-invasive.

Risks of MRI for Gallstones

  1. Contraindications. Due to the use of strong magnetic fields, MRI is not safe for everyone, particularly those who wear metallic implants or devices such as a pacemaker, cardiac defibrillator, cochlear implants, and implanted drug-infusion pumps. 

  2. Allergic reactions. While not always necessary, a gadolinium-based contrast agent (GBCA) may need to be injected into the bloodstream through an intravenous (IV) line to enhance the visibility of the gallbladder and bile or pancreatic ducts. There aren't many recorded incidences of adverse reactions, so the agent is considered safe. However, there's a risk of allergic reactions or adverse effects, particularly for pregnant women and people with kidney problems. 

  3. Claustrophobia. The enclosed structure of a traditional MRI machine may trigger anxiety and panic in people with claustrophobia. Opting for an open MRI scan is often the best option to minimise this risk. 

How long does an MRI of the gallbladder take?

On average, an MRI for gallbladder can take approximately 30 to 60 minutes to complete. 

Do you need an MRI for gallstones?

If you’re concerned about gallstones and want to find out if you have them, browse our network of over 150 scanning centres to book a private MRI gallbladder scan near you in a matter of minutes. And if you aren’t sure which scan to choose, why not book a phone consultation with one of our clinicians? For just £50, you’ll receive advice and guidance about which scan to choose, and, if you do decide to book a scan, we’ll discount your fee by £50 automatically.



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