Gallbladder, Imaging

Article Author:
Mark Jones
Article Editor:
Troy Ferguson
Updated:
11/3/2017 9:31:50 PM
PubMed Link:
Gallbladder, Imaging

Introduction

There are several variations and etiologies of gallbladder disease. Chronic and acute cholecystitis are the two ways this condition can present. Calculous and acalculous (with or without gallstones or cholelithiasis) are also variants of this disease. The most common form of gallbladder disease is chronic cholecystitis with cholelithiasis. Up to 15% of the population of the United States has asymptomatic gallstones. On the other hand, 15% of all cases of cholecystitis are acalculous or without stones.

Twenty to 25 million Americans have gallstones. Annually, more than 750,000 individuals undergo cholecystectomy in the United States. Many factors have been linked to gallbladder disease. Female gender, obesity, hormone exposure, diabetes, liver disease, age older than 40 years, and drastic weight loss are just a few factors that are associated with a higher incidence of gallbladder disease and gallstones.

Symptoms of cholecystitis must be distinguished from other conditions such as irritable bowel, peptic ulcer disease, gastroesophageal reflux disease, and cardiac issues.

Cases of chronic cholecystitis present as progressing right upper abdominal pain with bloating, food intolerances (especially greasy and spicy foods), increased gas, nausea, and vomiting. Pain in the midback or shoulder may also occur. This pain could be present for years until correctly diagnosed. Cases of acute cholecystitis have similar symptoms only more severe. Often, symptoms are mistaken for cardiac issues. The finding of right upper abdominal pain with deep palpation, Murphy's sign, is usually classic for this disease. Often, there is a specific dietary event leading to the acute attack, "I ate pork chops and gravy last night." The most important and useful test when diagnosing acute or chronic cholecystitis is a thorough history and physical exam performed by an experienced practitioner who is familiar with gallbladder disease.

Gallbladder cancer is somewhat rare, annually affecting 3 out of 100,000 individuals in the United States. It may present with symptoms similar to cholecystitis or may be asymptomatic until it becomes advanced.

Anatomy

Acute and chronic cholecystitis is caused by either a mechanical blockage of the biliary system, usually of the cystic duct, or by a functional hypokinetic condition of the gallbladder.

Gallstones most often cause mechanical anatomic blockages of the biliary outlet. Other etiologies responsible for mechanical obstruction are neoplasms, external compression, and stenosis of the bile duct.

Functional obstructions are caused by the hypokinetic emptying of the gallbladder from situations of decreased stimulus to the gallbladder such as in fasting states, critical illnesses, and nerve disruption associated with vagotomies, and gastric surgeries.

Plain Films

There are several diagnostic tests used make the determination of gallbladder disease. A simple abdominal x-ray can be used to identify calcified gallstones. Because only 10% of all gallstones are calcified, this imaging study has limited usefulness. Porcelain gallbladders can also be seen in plain x-rays. This condition is somewhat uncommon and results from calcification of the gallbladder wall. In 1924, two American surgeons developed the oral cholecystogram or OCG. The OCG is done by administering iopanoic acid by mouth. This is an iodine-based material that is absorbed by the intestines and concentrated in the gallbladder. When it combines with bile salts, it becomes a very radio-opaque liquid present within the gallbladder. This will outline any gallstones present in the gallbladder. The intervenous cholangiogram was developed in 1954. It was chiefly used to evaluate the bile ducts and to look for stones or strictures within these bile ducts. An iodine-based dye is injected intravenously. It is then concentrated in the liver and excreted into the bile ducts. The intervenous cholangiogram was a poor test to evaluate the actual gallbladder because sometimes the gallbladder was bypassed entirely as the dye went directly from the bile ducts into the small bowel. Both the oral cholecystogram and the intravenous cholecystogram are seldom used today.

Computed Tomography

Acute gallbladder disease, gallstones, polyps, and occasionally, gallbladder sludge, can be diagnosed with a CT scan. The scan is most often done when the patient is undergoing an initial workup in the emergency department, and the specific diagnosis is unclear. Pericholic fluid and a thickened gallbladder wall may be seen in cases of acute cholecystitis. Chronic cholecystitis may have nonspecific findings of a thickened gallbladder wall. Gallstones and gallbladder sludge may also be identified with a CT scan.

The CT scan is probably the most useful test when doing a workup for suspected gallbladder cancer. This test is noninvasive and can evaluate the size of the tumor, areas or metastasis, and whether or not there is a gross direct extension into the liver.

Magnetic Resonance

MRIs may identify the same findings as a CT scan. An MRCP (magnetic resonance cholangiopancreatogram) is a noninvasive imaging study useful when evaluating the biliary ducts. It can detect bile duct stones, strictures and neoplasms as small as several millimeters. An endoscopic retrograde cholangiopancreatogram (ERCP) is an invasive procedure that is also used to diagnose stones, strictures, and neoplasms of the biliary system. This procedure can also be used to treat and make a more definitive diagnosis by using biopsies, placing stents and removing retained bile duct stones. This does, however, add the risk of iatrogenic complications such as pancreatitis. Endoscopic ultrasonography is another procedure that allows good visualization of the bile ducts and pancreatic head.

Ultrasonography

The best diagnostic test to confirm gallbladder disease is the abdominal ultrasound. It is noninvasive and is 90% to 95% accurate in detecting gallstones. Pericholic fluid and thickened gallbladder walls can also be identified as in acute cholecystitis. Gallbladder sludge and occasionally common bile duct stones can also be seen with abdominal ultrasounds.

The gallbladder ultrasound may also be useful in detecting possible gallbladder neoplasms.

The EUS or endoscopic ultrasound is not a first-line test for diagnosing gallbladder disease. There is no place for it as a diagnostic tool for cholecystitis. It is useful when evaluating and staging tumors of the gallbladder, pancreas, and bile ducts. Biopsies can also be done for tissue diagnosis.

Nuclear Medicine

If acute cholecystitis is suspected and there is a negative gallbladder ultrasound, then a hepatobiliary iminodiacetic acid or HIDA scan is indicated. This is done by injecting technetium Tc 99m intravenously. It is taken up by the liver and excreted into the biliary system. If there is no filling of the gallbladder, then this would indicate complete mechanical or functional blockage of the cystic duct. This finding is close to 100% accurate for diagnosing acute cholecystitis. If a patient has characteristic symptoms of nonacute cholecystitis or biliary cholic and the gallbladder ultrasound is negative, they could have chronic acalculous cholecystitis. This is a functional problem caused by the hypokinetic emptying of the gallbladder. The best diagnostic test for this condition is a HIDA scan with KINAVAC (cholecystokinin-CCK). Tc 99m is administered as with a routine HIDA scan. Once the gallbladder is visualized, then the KINAVAC is administered intravenously. This simulates eating and causes the gallbladder to contract and empty. The percent that the gallbladder empties, called ejection fraction (EF), is measured digitally. An ejection fraction of below 30-35% is considered abnormal and possibly indicative of acalculous cholecystitis. Documented reproduction of symptoms with administration of the KINAVAC may also be indicative of gallbladder disease. Some studies have shown a 95% accuracy rate in detecting acalculous cholecystitis with a low EF in a HIDA scan. Other studies found that the accuracy of a HIDA scan may be altered in the presence of other ailments, especially other gastrointestinal (GI) conditions.

Clinical Significance

Correct imaging tests are vital when diagnosing cholecystitis or carcinoma of the gallbladder because a missed diagnosis could lead to a significant increase in patient morbidity and mortality. Various indications and knowledge of the appropriate tests to be ordered as well as obsolete tests are crucial when dealing with gallbladder disease.