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Imaging Tests of the Liver and Gallbladder

By

Christina C. Lindenmeyer

, MD, Cleveland Clinic

Last full review/revision Sep 2021| Content last modified Sep 2021
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Ultrasonography

Ultrasonography, traditionally done transabdominally and requiring a period of fasting, provides structural, but not functional, information. It is the least expensive, safest, and most sensitive technique for imaging the biliary system, especially the gallbladder. Ultrasonography is the procedure of choice for

The kidneys, pancreas, and blood vessels are also often visible on hepatobiliary ultrasounds. Ultrasonography can measure spleen size and thus help diagnose splenomegaly, which suggests portal hypertension Portal Hypertension Portal hypertension is elevated pressure in the portal vein. It is caused most often by cirrhosis (in developed countries), schistosomiasis (in endemic areas), or hepatic vascular abnormalities... read more .

Use of endoscopic ultrasonography may further refine the approaches to hepatobiliary abnormalities.

Ultrasonography can be difficult in patients with intestinal gas or obesity and is operator-dependent. Endoscopic ultrasonography incorporates an ultrasound transducer into the tip of an endoscope and thus provides greater image resolution even when intestinal gas is present.

Gallstones cast intense echoes with distal acoustic shadowing that move with gravity. Transabdominal ultrasonography is extremely accurate (sensitivity > 95%) for gallstones > 2 mm in diameter. Endoscopic ultrasonography can detect stones as small as 0.5 mm (microlithiasis) in the gallbladder or biliary system. Transabdominal and endoscopic ultrasonography can also identify biliary sludge (a mixture of particulate material and bile) as low-level echoes that layer in the dependent portion of the gallbladder without acoustic shadowing.

Cholecystitis typically causes

  • A thickened gallbladder wall (> 3 mm)

  • Pericholecystic fluid

  • An impacted stone in the gallbladder neck

  • Tenderness when the gallbladder is palpated with the ultrasound probe (ultrasonographic Murphy sign)

Extrahepatic obstruction is indicated by dilated bile ducts. On transabdominal and endoscopic ultrasounds, bile ducts stand out as echo-free tubular structures. The diameter of the common duct is normally < 6 mm, increases slightly with age, and can reach 10 mm after cholecystectomy. Dilated ducts are virtually pathognomonic for extrahepatic obstruction in the appropriate clinical setting. Ultrasonography can miss early or intermittent obstruction that does not dilate the ducts. Transabdominal ultrasonography may not reveal the level or cause of biliary obstruction (eg, sensitivity for common duct stones is < 40%). Endoscopic ultrasonography has a better yield.

Doppler ultrasonography

This noninvasive method is used to assess direction of blood flow and patency of blood vessels around the liver, particularly the portal vein. Clinical uses include

Computed tomography (CT)

CT is commonly used to identify hepatic masses, particularly small metastases, with a specificity of > 80%. CT with IV contrast is accurate for diagnosing cavernous hemangiomas of the liver as well as differentiating them from other abdominal masses. Neither obesity nor intestinal gas obscures CT images. CT can detect hepatic steatosis Nonalcoholic Fatty Liver Disease (NAFLD) Fatty liver is excessive accumulation of lipid in hepatocytes. Nonalcoholic fatty liver disease (NAFLD) includes simple fatty infiltration (a benign condition called fatty liver), whereas nonalcoholic... read more and the increased hepatic density that occurs with iron overload. CT is less helpful than ultrasonography in identifying biliary obstruction but often provides the best assessment of the pancreas.

Cholescintigraphy

After patients fast, an IV technetium-labeled iminodiacetic compound (eg, hydroxy or diisopropyl iminodiacetic acid [HIDA or DISIDA]) is injected; these substances are taken up by the liver and excreted in bile, then enter the gallbladder.

In acute calculous cholecystitis Acute Cholecystitis Acute cholecystitis is inflammation of the gallbladder that develops over hours, usually because a gallstone obstructs the cystic duct. Symptoms include right upper quadrant pain and tenderness... read more , which is usually caused by impaction of a stone in the cystic duct, the gallbladder does not appear on a scintigraphic scan because the radionuclide cannot enter the gallbladder. Such nonvisualization is diagnostically quite accurate (except for false-positive results in some critically ill patients). However, cholescintigraphy is rarely needed clinically to diagnose acute cholecystitis.

If acalculous cholecystitis is suspected, the gallbladder is scanned before and after administration of cholecystokinin (used to initiate gallbladder contraction). The decrease in scintigraphic counts indicates the gallbladder ejection fraction. Reduced emptying, measured as the ejection fraction, suggests acalculous cholecystitis.

Cholescintigraphy also detects bile leaks (eg, after surgery or trauma) and anatomic abnormalities (eg, congenital choledochal cysts, choledochoenteric anastomoses). After cholecystectomy, cholescintigraphy can quantitate biliary flow; biliary flow helps identify papillary stenosis (sphincter of Oddi dysfunction).

However, in acute or chronic cholestatic hepatic disorders, cholescintigraphy is not accurate as a diagnostic test because with cholestasis, hepatocytes excrete lower amounts of the radiotracer into the bile.

Radionuclide liver scanning

Ultrasonography and CT have largely supplanted radionuclide scanning, which had been used to diagnose diffuse liver disorders and mass lesions of the liver. Radionuclide scanning shows the distribution of an injected radioactive tracer, usually technetium (99mTc sulfur colloid), which distributes uniformly within the normal liver. Space-occupying lesions > 4 cm, such as liver cysts, abscesses, metastases, and tumors, appear as defects. Diffuse liver disorders (eg, cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic fibrosis that has resulted in widespread distortion of normal hepatic architecture. Cirrhosis is characterized by regenerative nodules surrounded by dense... read more , hepatitis Causes of Hepatitis Hepatitis is an inflammation of the liver characterized by diffuse or patchy necrosis. Hepatitis may be acute or chronic (usually defined as lasting > 6 months). Most cases of acute viral hepatitis... read more ) decrease liver uptake of the tracer, with more appearing in the spleen and bone marrow. In hepatic vein obstruction (Budd-Chiari syndrome Budd-Chiari Syndrome Budd-Chiari syndrome is obstruction of hepatic venous outflow that originates anywhere from the small hepatic veins inside the liver to the inferior vena cava and right atrium. Manifestations... read more ), liver uptake is decreased except in the caudate lobe because its drainage into the inferior vena cava is preserved.

Plain x-ray of the abdomen

Plain x-rays are not usually useful for diagnosis of hepatobiliary disorders. They are insensitive for gallstones Cholelithiasis Cholelithiasis is the presence of one or more calculi (gallstones) in the gallbladder. In developed countries, about 10% of adults and 20% of people > 65 years have gallstones. Gallstones tend... read more Cholelithiasis unless the gallstones are calcified and large. Plain x-rays can detect a calcified (porcelain) gallbladder. Rarely, in gravely ill patients, x-rays show air in the biliary tree, which suggests emphysematous cholangitis.

Magnetic resonance imaging (MRI)

MRI is used to image blood vessels (without using contrast), ducts, and hepatic tissues. MRI is superior to CT and ultrasonography for diagnosing diffuse liver disorders (eg, fatty liver Nonalcoholic Fatty Liver Disease (NAFLD) Fatty liver is excessive accumulation of lipid in hepatocytes. Nonalcoholic fatty liver disease (NAFLD) includes simple fatty infiltration (a benign condition called fatty liver), whereas nonalcoholic... read more , hemochromatosis Hereditary Hemochromatosis Hereditary hemochromatosis is a genetic disorder characterized by excessive iron (Fe) accumulation that results in tissue damage. Manifestations can include systemic symptoms, liver disorders... read more Hereditary Hemochromatosis ) and for clarifying focal defects (eg, liver tumors, hemangiomas). MRI also shows blood flow and therefore complements Doppler ultrasonography Doppler ultrasonography Imaging is essential for accurately diagnosing biliary tract disorders and is important for detecting focal liver lesions (eg, abscess, tumor). It is limited in detecting and diagnosing diffuse... read more Doppler ultrasonography and CT angiography CT angiography CT shows a focal area of osteolysis (arrows) involving the right acetabulum that is consistent with particle disease. In CT, an x-ray source and x-ray detector housed in a doughnut-shaped assembly... read more CT angiography in the diagnosis of vascular abnormalities and in vascular mapping before liver transplantation Liver Transplantation Liver transplantation is the 2nd most common type of solid organ transplantation. (See also Overview of Transplantation.) Indications for liver transplantation include Cirrhosis (70% of transplantations... read more .

Magnetic resonance cholangiopancreatography (MRCP) is more sensitive than CT or ultrasonography in diagnosing common bile duct abnormalities, particularly stones. Its images of the biliary system and pancreatic ducts are comparable to those obtained with endoscopic retrograde cholangiopancreatography Endoscopic retrograde cholangiopancreatography (ERCP) Imaging is essential for accurately diagnosing biliary tract disorders and is important for detecting focal liver lesions (eg, abscess, tumor). It is limited in detecting and diagnosing diffuse... read more Endoscopic retrograde cholangiopancreatography (ERCP) (ERCP) and percutaneous transhepatic cholangiography, which are more invasive. Thus, MRCP is a useful screening tool when biliary obstruction is suspected and before therapeutic ERCP (eg, for simultaneous imaging and stone removal) is done. MRCP is the screening test of choice for primary sclerosing cholangitis Primary Sclerosing Cholangitis (PSC) Primary sclerosing cholangitis (PSC) is patchy inflammation, fibrosis, and strictures of the bile ducts that has no known cause. However, 80% of patients also have inflammatory bowel disease... read more .

Endoscopic retrograde cholangiopancreatography (ERCP)

ERCP combines endoscopy through the second portion of the duodenum with contrast imaging of the biliary and pancreatic ducts. The papilla of Vater is cannulated through an endoscope placed in the descending duodenum, and the pancreatic and biliary ducts are then injected with a contrast agent.

ERCP provides detailed images of much of the upper gastrointestinal tract and the periampullary area, biliary tract, and pancreas. ERCP can also be used to obtain tissue for biopsy. ERCP is the best test for diagnosis of ampullary cancers. ERCP is as accurate as endoscopic ultrasonography for diagnosis of common duct stones. Because it is invasive, ERCP is used more for treatment (including simultaneous diagnosis and treatment) than for diagnosis alone. ERCP is the procedure of choice for treating biliary and pancreatic obstructing lesions, and for

Morbidity from a diagnostic ERCP with only injection of contrast material is about 1%. Adding sphincterotomy raises morbidity to 4 to 9% (mainly related to pancreatitis Overview of Pancreatitis Pancreatitis is classified as either acute or chronic. Acute pancreatitis is inflammation that resolves both clinically and histologically. Chronic pancreatitis is characterized by histologic... read more and bleeding). ERCP with manometry to measure sphincter of Oddi pressure causes pancreatitis in up to 25% of patients.

Percutaneous transhepatic cholangiography (PTC)

With fluoroscopic or ultrasound guidance, the liver is punctured with a needle, the peripheral intrahepatic bile duct system is cannulated above the common hepatic duct, and a contrast agent is injected.

PTC is highly accurate in diagnosing biliary disorders and can be therapeutic (eg, decompression of the biliary system, insertion of an endoprosthesis). However, ERCP is usually preferred because PTC causes more complications (eg, sepsis, bleeding, bile leaks).

Operative cholangiography

A radiopaque contrast agent is directly injected during laparotomy to image the bile duct system.

Operative cholangiography is indicated when jaundice Jaundice Jaundice is a yellowish discoloration of the skin and mucous membranes caused by hyperbilirubinemia. Jaundice becomes visible when the bilirubin level is about 2 to 3 mg/dL (34 to 51 micromol/L)... read more Jaundice occurs and noninvasive procedures are equivocal, suggesting common duct stones. The procedure can be followed by common duct exploration for removal of biliary stones. Technical difficulties have limited its use, particularly during laparoscopic cholecystectomy.

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