Imaging Tests of the Liver and Gallbladder

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 North America), schistosomiasis (in endemic areas), or hepatic vascular abnormalities. Consequences... read more .

Ultrasonography can be difficult in patients with intestinal gas or obesity and is operator-dependent. Endoscopic ultrasonography may provide improved resolution to hepatobiliary abnormalities. 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 (1 References 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 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 findings typically include

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 can be as low as 40%) (2 References 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 ultrasonography has a better yield.

Focal liver lesions > 1 cm in diameter can usually be detected by transabdominal ultrasonography. In general, cysts are echo-free; solid lesions (eg, tumors, abscesses) tend to be echogenic. Carcinoma appears as a nonspecific solid mass. Ultrasonography has been used to screen for hepatocellular carcinoma in patients at high risk (eg, with chronic hepatitis B Hepatitis B, Chronic Hepatitis B is a common cause of chronic hepatitis. Patients may be asymptomatic or have nonspecific manifestations such as fatigue and malaise. Diagnosis is by serologic testing. Without treatment... read more , 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 , or 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 ). Because ultrasonography can localize focal lesions, it can be used to guide aspiration and biopsy Liver Biopsy Liver biopsy provides histologic information about liver structure and evidence of liver injury (type and degree, any fibrosis); this information can be essential not only to diagnosis but also... read more .

Diffuse disorders (eg, cirrhosis, fatty liver Metabolic Dysfunction–Associated Liver Disease (MASLD) Steatotic liver disease is due to excessive accumulation of lipid in hepatocytes. Metabolic dysfunction–associated liver disease (MASLD) includes simple fatty infiltration (a benign condition... read more ) can be detected with ultrasonography.

Ultrasound elastography can measure liver stiffness as an index of hepatic fibrosis Hepatic Fibrosis Hepatic fibrosis is overly exuberant wound healing in which excessive connective tissue builds up in the liver. The extracellular matrix is overproduced, degraded deficiently, or both. The trigger... read more . In this procedure, the transducer emits a vibration that induces an elastic shear wave. The rate at which the wave is propagated through the liver is measured; liver stiffness speeds this propagation. Elastography is often used in combination with blood tests Laboratory Tests of the Liver and Gallbladder Laboratory tests are generally effective for the following: Detecting hepatic dysfunction Assessing the severity of liver injury Monitoring the course of liver diseases and the response to treatment... read more to assess hepatic fibrosis, particularly in patients with chronic hepatitis C Hepatitis C, Chronic Hepatitis C is a common cause of chronic hepatitis. It is often asymptomatic until manifestations of chronic liver disease occur. Diagnosis is confirmed by finding positive anti-HCV and positive... read more and nonalcoholic fatty liver disease Metabolic Dysfunction–Associated Liver Disease (MASLD) Steatotic liver disease is due to excessive accumulation of lipid in hepatocytes. Metabolic dysfunction–associated liver disease (MASLD) includes simple fatty infiltration (a benign condition... read more .

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

CT is commonly used to identify hepatic masses, particularly small metastases, with a specificity of ~ 80% (3 References 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 ). 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 Metabolic Dysfunction–Associated Liver Disease (MASLD) Steatotic liver disease is due to excessive accumulation of lipid in hepatocytes. Metabolic dysfunction–associated liver disease (MASLD) includes simple fatty infiltration (a benign condition... 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.

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 Metabolic Dysfunction–Associated Liver Disease (MASLD) Steatotic liver disease is due to excessive accumulation of lipid in hepatocytes. Metabolic dysfunction–associated liver disease (MASLD) includes simple fatty infiltration (a benign condition... 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 ) 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 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 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 (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 and has largely supplanted the use of HIDA (hydroxy or diisopropyl iminodiacetic acid) scans. 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 with PSC also have inflammatory bowel... read more .

ERCP 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 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.

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).

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 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.

With the increasing availability of MRCP, the usefulness of HIDA scan has decreased significantly. Cholescintigraphy is done after the patient fasts. 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.

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 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-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. Gallstones tend to be asymptomatic. The most common symptom is biliary colic; gallstones do not cause dyspepsia... read more unless the gallstones are calcified and large. Plain x-rays can detect a calcified (porcelain) gallbladder Tumors of the Gallbladder and Bile Ducts Gallbladder and bile duct tumors can cause extrahepatic biliary obstruction. Symptoms may be absent but often are constitutional or reflect biliary obstruction. Diagnosis is based on ultrasonography... read more . Rarely, in gravely ill patients, x-rays show air in the biliary tree, which suggests emphysematous cholangitis.