Introduction
Gallbladder ultrasound is a non-invasive, painless procedure to image the gallbladder and helps diagnose related disorders. During this procedure, a gel is applied to the area of the skin to be examined (right quadrant of the abdomen). Then, the doctor presses a handheld device called a transducer against the skin that sends sound waves and collects the bounced back waves, and the computer processes the waves to produce images.
What Is Gallbladder?
The gallbladder is an internal organ that serves as a storage bag for the bile juice produced by the liver. It is a pear-shaped organ located under the right lobe of the liver. It measures around seven to ten centimeters in length and four centimeters in width. The structure of the gallbladder is divided into three parts- neck, body, and fundus. The neck is connected to the cystic duct, which joins the other two ducts of the biliary tree – The common hepatic duct and the common bile duct. The common bile duct drains into the duodenum (small intestine). There is a dilatation at the opening of the cystic duct called Hartmann’s pouch.
What Are the Functions of The Gallbladder?
The primary function of the gallbladder is to store bile produced by the liver to aid the body in digesting fat. It can store up to 50 ml of bile juice at a time. When food containing fats reaches the small intestine, signals reach the gallbladder, and it empties its content into the small intestine and breaks down the fats. Bile juice is made up of water and bile salts. Besides storing, the gallbladder increases the concentration of the bile juice by removing water and electrolytes.
What Is Gallbladder Ultrasound?
Ultrasonography can produce images of the soft tissues and internal organs in the body without radiation. It utilizes high-frequency sound waves and can produce moving pictures of internal organs like the heartbeat and blood flow through blood vessels. Ultrasound can help diagnose the following disorders of the gallbladder:
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Cholecystitis: A condition caused due to stones blocking the tube that leads to the small intestine from the gallbladder.
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Emphysematous Cholecystitis: A life-threatening condition, caused by gas-forming organisms in acute infection of the gallbladder.
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Gallbladder Polyps: Abnormal tissue growth that protrudes inside the mucosal lining of the gallbladder.
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Porcelain Gallbladder: A condition where the inner gallbladder wall is encrusted by calcium.
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Gallbladder Perforation: It is a complication of acute cholecystitis, it has high mortality and morbidity rate.
How Does a Normal Gallbladder Appear in Ultrasound?
Normal gallbladder appears as an anechoic (black and dark) pear-shaped structure varying in size according to the amount of bile juice in it. It is thin-walled (less than three millimeters) and located in the right upper quadrant of the abdomen.
What Are the Variants Seen in Normal Gallbladder Ultrasound?
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Folds - They are commonly seen in the ultrasound protruding into the pear-shaped black space and are normal. The presence of small calculi (stones) along the folds should be assessed.
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The Phrygian Cap - Refers to the inversion of the fundus of the gallbladder into the body. It appears as a conical cap at the fundus end.
What Is a Wall-Echo-Shadow Sign?
Stones in the gallbladder are confirmed with WES (wall-echo-shadow) sign. The following are four features of the wall-echo-shadow sign:
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A hyperechogenic line indicates the gallbladder wall.
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A thin hypoechogenic line indicates bile juice.
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The hyperechogenic line indicates the near-surface of gallstones.
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The acoustic shadow is distal to the gallstone surface.
How to Prepare the Patient for an Ultrasound?
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The patient should be instructed to fast for six to eight hours.
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Morning appointments should be preferred to prevent gastric problems.
What Is Cholecystitis?
Cholecystitis is the inflammation of the gallbladder. The inflammation is due to the inability of the gallbladder to empty bile juice caused by obstruction of the cystic duct. The obstruction of the cystic duct is primarily due to bile stones (calculi). Cholecystitis may be acute or chronic:
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Acute Cholecystitis - Appears as sudden severe pain in the right or mid-abdomen. In some extreme cases, the wall of the gallbladder is ruptured, and the bile juice is emptied into the abdominal cavity causing severe pain. Such conditions can be fatal and require immediate medical intervention.
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Chronic Cholecystitis- Appears as recurrent mild pain and swelling in the right abdomen. Here, the gallbladder wall tends to shrink or lose elasticity, decreasing the functioning capacity of the gallbladder.
Cholecystitis can be detected by ultrasound, computed tomography (CT) scan, magnetic resonance imaging (MRI), and nuclear imaging.
What Are Ultrasound Findings in Cholecystitis?
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Stones in gallbladder.
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Thickened gallbladder wall (greater than three millimeters).
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Positive sonographic Murphy’s sign - The patient is asked to breathe in, and while breathing out, tenderness (pain) over the gallbladder region is felt when the physician's hand or ultrasound transducer touches the gallbladder.
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The presence of fluid around the gallbladder (pericholecystic fluid).
How Does Gallbladder Perforation Occur?
Gall bladder perforation is a complication of acute cholecystitis. Blockage of the cystic duct can lead to increased pressure inside the gallbladder, which in turn cuts the blood supply causing necrosis of the gallbladder wall and perforation. This condition can also be physician induced while performing a laparoscopy of the abdomen. There are four clinical subtypes of gallbladder perforation.
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Type 1 - Acute free perforation.
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Type 2 - Subacute pericholecystic abscess.
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Type 3 - Chronic cholecystoenteric fistulation.
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Type 4 - Colecystobiliary fistula formation.
Ultrasound images of gallbladder perforation display pericholecystic fluid collections (fluid around the gallbladder) in gallbladder perforation.
What Is Emphysematous Cholecystitis?
Emphysematous cholecystitis is a form of acute cholecystitis. It is characterized by necrosis of the gallbladder wall resulting in gas formation in the lumen or wall. It is a life-threatening condition and requires immediate surgery.
What Are Ultrasound Findings in Emphysematous Cholecystitis?
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Champagne Sign - Small echoic foci rising from the affected gallbladder wall (like effervescing bubbles in champagne).
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Stones - They are found in the lumen of the gallbladder.
What Are Gallbladder Polyps?
Gallbladder polyps are the lesions that arise from the gallbladder wall and project inside it.
It can be benign or malignant. Benign gallbladder polyps are false tumors that do not spread or invade other body organs. Cholesterol polyps, inflammatory polyps, and hyperplasia are some benign polyps. Malignant gallbladder polyps are carcinomas that can spread or invade other body parts. Gallbladder polyps are asymptomatic in most cases and coincidently diagnosed during an ultrasound of the abdomen or after surgical removal of the gallbladder. Fever, abdominal pain, and loss of appetite are some common symptoms. Cholesterol polyp sometimes detaches from the wall, blocks the cystic duct, and causes cholecystitis.
What Are Ultrasound Findings in Gallbladder Polyps?
Ultrasound can depict the gallbladder polyp's location, number, and size. Ultrasound can detect polyps that are at least 5 millimeters in diameter. The gallbladder polyp appears immobile, hyperechoic structure with or without shadow protruding into the gallbladder. The cholesterol polyp appears with the same echogenicity as the gallbladder wall. Ultrasound cannot differentiate malignant from benign polyps, whereas high-resolution ultrasonography (HRUS) differentiates malignant from benign polyps. High-resolution ultrasonography can image the following features of malignant polyps:
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Size more than one centimeter.
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Lobulated surface contour (multiple small well-demarcated outpouchings).
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The presence of branching vessels is seen on the color doppler.
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Hypoechoic foci (strong predictive factor of neoplastic gallbladder polyps) within the polyp.
What Is a Porcelain Gallbladder?
Deposition of calcium salts (cholesterol in some cases) in the gallbladder wall makes it fragile and brittle. The condition is called porcelain gallbladder and is usually asymptomatic. It is diagnosed coincidentally in an abdomen ultrasound, CT, MRI, or surgery. The calcium deposits can involve either the entire wall or patches of wall. This condition has a high risk of developing into a carcinoma.
What Are Ultrasound Findings of a Porcelain Gallbladder?
The porcelain gallbladder shows echoes and dense posterior shadowing, with usually poor delineation of the gallbladder wall. Generally, gallstones can be misdiagnosed as porcelain gallbladder. In such cases, the physician should look after the presence of the WES sign that is positive in cases of gallstones and negative in cases of porcelain gallbladder.
Conclusion
Ultrasound is used as an initial diagnostic tool in detecting any problems related to the gallbladder. It is also a cheap and less time-consuming procedure. Recent advances like high-resolution ultrasound and 3D ultrasounds also improved sureness in diagnosing gallbladder disorders. They provide high-resolution images and aid in diagnosing gallbladder cancers. However, a trained radiologist is essential to interpret the findings and arrive at a proper diagnosis.
