Liver and Biliary Tract Imaging

The hepatobiliary system is composed of the liver, gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract, and bile ducts (within the liver and external to the liver). The liver produces bile, which is a fluid made of cholesterol, phospholipids, conjugated bilirubin, bile salts, electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes, and water. Bile, which assists in digestion Digestion Digestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body. Digestion and Absorption and helps eliminate waste products, is stored in the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract. The hepatobiliary system can be affected by infections, cysts, solid masses, ischemia, and mechanical flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure obstruction, which mandate the presence of reliable imaging tests to determine the etiology. The methods that evaluate structural changes in the liver and biliary tract include ultrasonography, CT scan, and MRI (including magnetic resonance cholangiopancreatography). Additionally, cholescintigraphy, a functional imaging study, helps identify gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract pathology by tracking the biliary pathway.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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Introduction

Imaging methods

  • The common radiologic methods used to evaluate the liver and biliary tract:
    • Ultrasonography (US)
    • CT
    • MRI
    • Nuclear imaging Nuclear Imaging Nuclear imaging is the radiologic examination using radiopharmaceuticals, which are radioactive substances taken up by specific types of cells. Nuclear medicine is more concerned with the functional and molecular aspects of the organ or pathology being investigated rather than the structure. Nuclear Imaging
  • For hepatobiliary imaging, radiography does not play as important a role as it does for imaging of the chest, urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract, or skeletal system.

Preparation and orientation

Prior to interpretation of any image, the physician should take certain preparatory steps. The same systematic approach should be followed every time.

  • Confirm name, date, and time on all images.
  • Obtain knowledge of patient’s medical history and physical examination.
  • Confirm appropriate exam and technique for desired pathology.
  • Compare any available images of the same area taken using the same method.
  • Determine orientation of image:
    • In the United States, standard exam views place a marker (dot) to the patient’s right.
    • For CT/MRI: On axial view, the image is sliced and viewed from inferior to superior (as if you are looking from the feet up).
  • Fasting is recommended before performing abdominal US, CT, and MRI.

Ultrasonography

Overview

  • Medical indications:
    • Emergency care:
      • Trauma with concern for hepatobiliary injury
      • Concern for biliary obstruction
      • Concern for hepatic abscess
      • Evaluation for cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis
    • Routine care:
      • Signs and symptoms of liver failure/chronic liver disease
      • Evaluation of hepatic steatosis
      • Screening for neonates with abnormalities noted on prenatal US (biliary atresia)
    • Monitoring: known cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis to evaluate for hepatocellular carcinoma Hepatocellular carcinoma Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases ( HCC HCC Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases
  • Advantages:
    • Low cost 
    • No radiation dose 
    • Widespread availability
    • Fast
  • Disadvantages:
    • Poor resolution 
    • Narrow field of view
    • Individual must hold still for procedure.
    • Technician-dependent

Exam technique

  • Positioning:
    • Individual:
      • Access to the RUQ abdomen
      • Maximize contact between individual’s skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin and US probe
    • Visualization: The liver should be most superficial to the probe, with no other organs/bowel between it and the US probe.
  • Depth and gain: 
    • Determines the field of view and echogenicity characteristics of the tissue
    • Gain (amplification of signals) is adjusted so that the parenchyma is visualized without saturating out too much signal.

Interpretation and evaluation

Report includes:

  • Size
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver:
      • Normal liver span is usually < 16 cm in the midclavicular line (may vary by sex and body size).
      • Variant anatomy includes a Riedel lobe, caudate lobe papillary process, and accessory hepatic lobe(s). 
    • Gallbladder:
      • Transverse dimension: 4 cm 
      • Length is more variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables: generally ≤ 10 cm
      • Wall thickness should be ≤ 3 mm.
  • Echogenicity:
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver parenchyma:
      • Homogeneous in echotexture
      • Usually isoechoic (same brightness) or slightly hyperechoic (brighter or white on the screen) as compared with the right kidney
    • Gallbladder is anechoic (black on the screen).
  • Position:
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: inferior to the right hemidiaphragm
    • Gallbladder: found in gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract fossa (under the right lobe of the liver)
  • Abnormalities found
Liver and biliary system

Anatomy of the liver and the biliary system

Image by Lecturio.

Normal findings

  • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver:
    • Normal liver size is < 16 cm in the midclavicular line.
    • Variant anatomy such as Riedel lobe (congenital elongation of the right hepatic lobe):
      • Can give an impression of hepatomegaly 
      • Cross-sectional imaging (e.g., CT) can confirm the benign anatomy.
  • Gallbladder:
    • Dimension (4 cm in diameter) and wall thickness (≤ 3 mm)
    • Anechoic
    • Thin homogeneous wall
    • Without stones or sludge
  • Bile ducts are thin tubes (no larger than the associated intrahepatic portal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins or hepatic arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries). 
    • As ducts extend from the liver (to the sphincter of Oddi), the caliber increases.
    • Extrahepatic ducts: The common hepatic duct and the cystic duct (from the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract) form the common bile duct common bile duct The largest bile duct. It is formed by the junction of the cystic duct and the common hepatic duct. Acute Cholangitis
    • Common bile duct (CBD) should be < 6 mm in diameter in those 60 years of age or younger.
      • Add 1 mm for every decade after 60 years of age (e.g., 7 mm for 70s, 8 mm for 80s).
      • Postcholecystectomy status can cause enlargement of the CBD, termed the “reservoir effect.”
Normal liver

Normal liver ultrasound showing a homogeneous parenchyma

Image: “Normal liver” by Fuster, D. et al. License: CC BY 3.0

CT

Overview

  • Medical indications:
    • Follow-up of suspicious US imaging:
      • Hypoechoic/hyperechoic lesions
      • Concern for vascular pathology
      • Contour deformities
      • Bile duct dilation
      • Fluid collections
    • Malignancy:
      • Evaluate initial staging Staging Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis of HCC HCC Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases
      • Surveillance for recurrence of disease
      • Tumor vein thrombosis
    • Major trauma:
      • Evaluation of hepatic parenchyma
      • Evaluation for hepatic hemorrhage +/– active extravasation on delayed images
      • Concern for subtle pathology not seen on US
  • Advantages:
    • Excellent resolution of anatomical detail 
    • Structures can be seen in 3 dimensions.
  • Disadvantages: 
    • Involves high radiation dose
    • Individual must hold still for exam.
    • Expensive to perform

Exam technique

  • Standard CT scanning:
    • Individual lies supine on table. 
    • Table is moved in CT scanner, which rotates around the individual.
    • Individual is instructed to hold breath and remain still for scan (for seconds)
    • Exams can be done with or without IV or oral contrast.
    • Timing of injection of IV contrast dye can help direct radiologic inquiry of certain areas of pathology:
      • CT with IV contrast is typically performed in the portal venous phase initially.
      • Another set of images is obtained at a later time point to evaluate for active extravasation.

Interpretation and evaluation

  • Interpretation should follow a systematic and reproducible pattern
  • Review individual’s history and physical examination findings.
  • Ideal evaluation with soft-tissue window/level
  • Compare to available recent image of are of interest.
  • Orient image:
    • Axial images are viewed as if looking from the feet up.
    • Sagittal and coronal 
  • Identify landmark anatomical structures
  • Observe for “continuity” of parenchyma while scrolling through image slices.

Normal findings

  • Normal liver:
    • RUQ location
    • < 16 cm in craniocaudal dimension at the midclavicular line
    • Divided into right and left hepatic lobes by the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract fossa
    • Attenuation: 50–75 Hounsfield units (HU) in noncontrast CT scan
  • Normal gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract:
    •  ≤ 4 cm in diameter
    • Wall thickness ≤ 3 mm
  • Intrahepatic ducts are very small and are faintly visualized in contrast studies.
  • Common bile duct should be < 6 mm in diameter in patients 60 years of age or younger.
    • As in US, an increase in diameter is noted with an increase in age.
    • Postcholecystectomy status can cause enlargement of the extrahepatic bile ducts Extrahepatic bile ducts Passages external to the liver for the conveyance of bile. These include the common bile duct and the common hepatic duct. Gallbladder and Biliary Tract.
Ct scan of the liver

A normal contrast-enhanced CT scan of the liver:
K: kidney
L: liver
P: pancreas Pancreas The pancreas lies mostly posterior to the stomach and extends across the posterior abdominal wall from the duodenum on the right to the spleen on the left. This organ has both exocrine and endocrine tissue. Pancreas
St: stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach
Sp: spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen

Image: “FIGURE 1” by Faraji, F. and Gaba R.C. License: CC BY 4.0

MRI

Overview

  • Medical indications:
    • Detailed evaluation of hepatic lesions
      • Hemangiomas
      • Cysts
      • HCC HCC Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases
      • Metastasis
      • Indeterminate lesions noted incidentally on US and CT
  • Advantages:
    • Provides higher level of imaging and detail of fluid, enhancement, and soft tissue
    • Can be used for evaluation of pregnant individuals
    • Used as adjunct to previous test (US or CT)
  • Disadvantages:
    • ↑↑↑ Cost
    • Takes much longer to perform than CT or US
    • Not suitable for all individuals:
      • Implants (particularly metal) distort the image.
      • Requires individual to be in loud, enclosed space
      • The individual must stay still for adequate imaging.

Exam technique

  • Positioning:
    • Supine on table
    • Table is advanced into the scanner.
    • Individual must remain still during scanning.
  • Views:
    • T1-weighted images: 
      • Lesions with high fat content (e.g., lipoma Lipoma A lipoma is a benign neoplasm of fat cells (adipocytes) and the most common soft tissue tumor in adults. The etiology is unknown, but obesity is a predisposing factor; genetics also play a role, with multiple lipomas occurring in various inherited disorders. Lipoma) appear bright/white, and compartments filled with water appear dark/black.
      • Postcontrast images are typically T1-weighted owing to the intrinsic properties of gadolinium. 
    • T2-weighted images: compartments filled with water appear bright/white.
    • Images oriented in 3-dimensional “slices”: 
      • Coronal 
      • Sagittal
      • Axial
Table: General principles of MRI images
Tissue T1-weighted images T2-weighted images
Fluid (e.g., CSF) Dark Bright
Fat Bright Bright
Inflammation Dark Bright

Interpretation and evaluation

  • Interpretation should follow a systematic and reproducible pattern.
  • Review history and examination findings.
  • Compare to available recent imaging of the area of interest.
  • Orient image.
  • Identify landmark anatomical structures
  • Observe for continuity of structures while scrolling through image slices.

Normal findings

  • Normal liver MRI appearance 
    • RUQ location
    • Smooth borders
    • Homogeneous parenchymal signal
    • T1-weighted intensity: 
      • Isointense to the paraspinal muscles
      • Slightly more intense than the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen and kidney
    • T2-weighted intensity:
      • Less intense than the kidney
      • Hepatic cysts, biliary hamartomas, abscesses, and hemangiomas are bright (compared to liver).
    • Contrast:
      • Arterial phase: heterogeneous enhancement
      • Venous phase: homogeneous enhancement of the liver
      • Late phase gives information regarding lesion washout or late enhancement.
      • Similar to CT pattern
    • Signal intensity of the normal liver parenchyma is the same on in-phase and out-of-phase imaging.
  • Biliary tracts:
    • Intrahepatic ducts are very small and are faintly visualized in contrast studies.
    • CBD: < 6 mm generally, but affected by age and prior cholecystectomy Cholecystectomy Cholecystectomy is a surgical procedure performed with the goal of resecting and extracting the gallbladder. It is one of the most common abdominal surgeries performed in the Western world. Cholecystectomy is performed for symptomatic cholelithiasis, cholecystitis, gallbladder polyps > 0.5 cm, porcelain gallbladder, choledocholithiasis and gallstone pancreatitis, and rarely, for gallbladder cancer. Cholecystectomy: Approaches and Technique
  • Magnetic resonance cholangiopancreatography (MRCP)
    • Used for those with suspected pancreaticobiliary disease and with conditions that preclude endoscopic retrograde cholangiopancreatography (ERCP)
    • Heavily T2-weighted images (pancreatic and bilious fluid are bright)
    • A calculus or mass would produce a signal void.

Nuclear Imaging

Overview

Nuclear medicine differs from the rest of radiology because it is functional, rather than structural, imaging.

  • Hepatobiliary iminodiacetic acid (HIDA) scan (or cholescintigraphy):
    • Examination of the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract
    • The radiopharmaceutical is normally taken up by the liver and excreted through the biliary system as bile.
  • Indications: 
    • Acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis with equivocal US findings
    • Biliary atresia
    • Biliary leak
    • Biliary dyskinesia (cholecystokinin administered and gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract ejection fraction calculated)
  • Contraindication: allergy to the radiotracer (may cause anaphylaxis)

Exam technique

  • The individual lies supine on a table.
  • Use of radiopharmaceuticals:
    • Artificially produced isotopes bound to pharmaceuticals (radioisotope + organic molecule) 
    • Administered IV
    • Organic molecule allows isotopes to concentrate within the liver and biliary tracts (tracing the path of bile).
    • The radioisotope emits detectable ionizing radiation (high-energy rays) when it decays, and this is seen in the imaging.
  • The machine is equipped with a gamma camera that detects the radiation, forming an image.
    • Images are obtained at different times.
    • Signals from different areas of the biliary tract (e.g., the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract, common bile duct common bile duct The largest bile duct. It is formed by the junction of the cystic duct and the common hepatic duct. Acute Cholangitis, and duodenum) are reviewed.

Normal findings

  • Patent cystic duct: The tracer will enter the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract, making the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract visualizable.
  • Patent CBD and ampulla: 
    • Contrast visualization noted within the CBD, gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract, and small bowel occurs within 30–60 minutes
    • Delayed images can be obtained (3–4 hours), or morphine augmentation can be done if the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract is not seen.
    • If the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract is not seen in the delayed images, results are consistent with acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis.

Different results

Table: Interpretation
Imaging finding What it means
Bile ducts visible Normal hepatic function
Filling of the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract Patent cystic duct
Radiotracer seen in the duodenum Patent common bile duct common bile duct The largest bile duct. It is formed by the junction of the cystic duct and the common hepatic duct. Acute Cholangitis
No radiotracer seen in the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract Obstructed gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract (acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis)
No radiotracer seen in the duodenum Biliary atresia
Radiotracer outside the biliary system Biliary leak
Normal hepatobiliary iminodiacetic acid scan

Normal hepatobiliary iminodiacetic acid scan showing the radioactive substance moving through the biliary system

Image: “HIDA” by Myo Han. License: CC BY 3.0

Abnormal Findings

Hepatic steatosis

  • US:
    • Increased parenchymal echogenicity
    • Causes loss of visualization of the portal triads
    • Severe steatosis causes sound-beam attenuation, which will obscure visualization of the deep portions of the liver.
  • CT:
    • Decreased attenuation of the hepatic parenchyma due to fatty infiltration (steatosis):
      • Defined as a Hounsfield unit (HU) value of 10 below that of the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen on noncontrast exams
      • A relative value < 40 HU is also acceptable on noncontrast exams
    • Can produce the appearance of hyperdense vessels within the liver on noncontrast examinations
    • May obscure lesions that are normally hypodense compared to background liver
  • MRI: Fatty infiltration of the liver leads to loss of signal on out-of-phase imaging relative to in-phase imaging.

Cholecystitis and cholelithiasis Cholelithiasis Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). Cholelithiasis

  • US:
    • Most sensitive findings:
      • Cholelithiasis
      • Gallbladder distention
      • Positive Murphy sign
    • Other findings:
      • Pericholecystic fluid (double-wall sign)
      • Wall thickening > 3 mm
    • Emphysematous cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis produces multiple foci of internal air, which obscure underlying detail owing to shadowing.
  • CT:
    • Cholelithiasis: stones can be invisible on CT because there is little difference in density between bile and stones.
    • Stones within the bile duct are consistent with choledocholithiasis.
    • Cholecystitis: gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract distention and wall thickening with pericholecystic inflammatory changes
  • MRI: highest sensitivity for detecting choledocolithiasis as filling defects on heavily weighted T2 imaging
  • HIDA: gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract not seen in delayed images

Cirrhosis

  • US:
    • Nodular liver contour
    • Increased echogenicity
    • Right hepatic lobe atrophy with caudate lobe hypertrophy
    • In advanced disease, shrunken liver is noted.
    • Associated with portal hypertension Portal hypertension Portal hypertension is increased pressure in the portal venous system. This increased pressure can lead to splanchnic vasodilation, collateral blood flow through portosystemic anastomoses, and increased hydrostatic pressure. There are a number of etiologies, including cirrhosis, right-sided congestive heart failure, schistosomiasis, portal vein thrombosis, hepatitis, and Budd-Chiari syndrome. Portal Hypertension:
      • Collateral veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins
      • Increased portal vein Portal vein A short thick vein formed by union of the superior mesenteric vein and the splenic vein. Liver diameter
      • Decreased flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure in the portal circulation (detected by Doppler imaging)
    • Ultrasonography is also used in estimating liver stiffness (liver fibrosis): elastography
  • CT (not routinely used to evaluate cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis):
    • Right hepatic lobe atrophy, caudate lobe hypertrophy
    • Nodular liver contour
    • Signs of portal hypertension Portal hypertension Portal hypertension is increased pressure in the portal venous system. This increased pressure can lead to splanchnic vasodilation, collateral blood flow through portosystemic anastomoses, and increased hydrostatic pressure. There are a number of etiologies, including cirrhosis, right-sided congestive heart failure, schistosomiasis, portal vein thrombosis, hepatitis, and Budd-Chiari syndrome. Portal Hypertension
      • Dilated portal vein Portal vein A short thick vein formed by union of the superior mesenteric vein and the splenic vein. Liver
      • Varices
      • Ascites
      • Splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly
  • MRI:
    • Unclear role in the diagnosis of cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis (information can also be obtained from other imaging studies)
      • May help in cases of iron overload (estimate of hepatic iron concentration)
      • MRA is also more sensitive for portal vein Portal vein A short thick vein formed by union of the superior mesenteric vein and the splenic vein. Liver thrombosis, a complication of cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis.
      • MR elastography is also used to measure liver fibrosis.

Hepatocellular carcinoma

  • US:
    • Any lesion in an individual with cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis is suspicious.
    • Can be hyperechoic or hypoechoic with a surrounding halo of edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
  • CT:
    • Enhancing lesion in an individual with cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis is suspicious for HCC HCC Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases.
    • Shows arterial enhancement with rapid washout
  • MRI:
    • Shows arterial enhancement with rapid washout
    • Rim enhancement on delayed postcontrast images causing a capsule appearance

Abscess

  • US:
    • Pyogenic abscess has varying appearances, ranging from hypoechoic to hyperechoic lesions.
    • Internal echoes (from debris and/or septations) can be visualized.
  • CT (with contrast):
    • Well-defined round lesion, but complex abscesses can have irregular borders
    • Central hypoattenuation
  • MRI:
    • T1-weighted imaging: central low signal intensity
    • T2-weighted imaging: high signal intensity

Hemangioma

  • US:
    • Noncontrast: hyperechoic homogeneous focus that is well defined relative to background liver
    • Contrast: In the arterial phase, there is peripheral nodular enhancement.
    • Doppler can show the blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure within the hemangioma.
    • Can be obscured in steatosis
  • CT:
    • Early phase: peripheral nodular enhancement
    • Late phase: “filling in” or centripetal pattern
  • MRI:
    • Well-demarcated homogeneous mass 
    • Hypointense lesion on T1-weighted images
    • High signal intensity on T2-weighted images
    • With contrast: peripheral nodular enhancement, with progression centripetally

Other benign liver lesions

  • Focal nodular hyperplasia:
    • US:
      • Noncontrast: isoechoic mass
      • With contrast: enhancement sustained in arterial phase, with central arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries seen with spoke-and-wheel pattern on arterial phase (centrifugal)
    • CT scan:
      • Precontrast: isodense
      • With contrast: homogeneous hyperdense lesion in the arterial phase, becoming isodense (like the liver parenchyma) in the venous phase
      • The central scar becomes hyperdense on delayed imaging.
    • MRI scan: 
      • Highest diagnostic accuracy
      • Precontrast: isointense on T1-weighted images; slightly hyperintense on T2-weighted images
      • With contrast: early homogeneously enhanced mass (arterial phase), becoming an isointense mass (delayed phase)
      • Enhancement of the central scar noted in the delayed phase.
    • Nuclear medicine (technetium-99m sulfur colloid scan): 
      • Increased uptake of sulfur colloid (Kupffer cell activity) is seen in 60%–70% of cases. 
      • Helps in differentiation from adenoma (which has no Kupffer cell activity)
  • Hepatic adenoma:
    • US: 
      • Without contrast: nonspecific heterogeneous mass
      • With contrast: rapid hyperenhancement from periphery to center (centripetal)
    • CT scan: 
      • Without contrast: isodense lesion
      • With contrast: may have peripheral enhancement (arterial phase), then will have centripetal flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure (portal venous phase)
      • If there are areas of hemorrhage, necrosis, and calcification, adenoma appears heterogeneous.
    • MRI with contrast:
      • Superior to other methods for HCC HCC Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases diagnosis
      • Arterial phase: well-demarcated, enhanced lesion (heterogeneous due to hemorrhage, necrosis, steatosis)
      • Pattern in later phases correlates with molecular subtypes in majority of cases.
    • Will typically show no uptake on nuclear medicine technetium-99m sulfur colloid scan

References

  1. Chopra, S. (2021) Focal nodular hyperplasia. UpToDate. Retrieved December 18, 2021, from https://www.uptodate.com/contents/focal-nodular-hyperplasia
  2. Curry, M., Bonder, A. (2021) Overview of the evaluation of hepatomegaly. UpToDate. Retrieved December 16, 2021, from https://www.uptodate.com/contents/overview-of-the-evaluation-of-hepatomegaly-in-adults
  3. Curry, M., Chopra, S. (2021) Hepatic hemangioma. UpToDate. Retrieved December 18, 2021, from https://www.uptodate.com/contents/hepatic-hemangioma
  4. Gill, R.M., Kakar, S. (2020). Liver and gallbladder. In: Kumar, V., Abbas, A. K., Aster, J.C. (Eds.), Robbins & Cotran Pathologic Basis of Disease, 10th ed. Elsevier, pp. 868–872.
  5. Goldberg E., Chopra S. (2021). Cirrhosis in adults: etiologies, clinical manifestations, and diagnosis. UpToDate. Retrieved July 17, 2021, from https://www.uptodate.com/contents/cirrhosis-in-adults-etiologies-clinical-manifestations
  6. Hundt, M., Wu, C.Y., Young, M. (2021) Anatomy, abdomen and pelvis, biliary ducts. StatPearls. Retrieved December 21, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK459246/
  7. Perret, R.S., Sloop, G.D., Borne, J.A. (2000) Common bile duct measurements in an elderly population. J Ultrasound Med 19:727–731. doi: 10.7863/jum.2000.19.11.727.
  8. Schwartz, J.M., Carithers, R.L. (2020). Epidemiology and risk factors for hepatocellular carcinoma. UpToDate. Retrieved July 17, 2021, from https://www.uptodate.com/contents/epidemiology-and-risk-factors-for-hepatocellular-carcinoma?topicRef=16348&source=see_link
  9. ​​Skoczylas, K., Pawełas, A. (2015). Ultrasound imaging of the liver and bile ducts—expectations of a clinician. J Ultrasonogr 15:292–306. https://doi.org/10.15557/JoU.2015.0026
  10. Snyder, E., Kashyap, S., Lopez, P.P. (2021). Hepatobiliary iminodiacetic acid scan. StatPearls. Retrieved December 21, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK539781/
  11. Vollmer, C., Zakko, S., Afdhal, N. (2019) Treatment of acute calculous cholecystitis. UpToDate. Retrieved July 17, 2021, from https://www.uptodate.com/contents/treatment-of-acute-calculous-cholecystitis
  12. Vu, L. N., Morelli, J. N., Szklaruk, J. (2018). Basic MRI for the liver oncologists and surgeons. J Hepatocell Carcinoma 5:37–50. https://doi.org/10.2147/JHC.S154321
  13. Wells, M. M., Li, Z., Addeman, B., McKenzie, C. A., Mujoomdar, A., Beaton, M., Bird, J. (2016). Computed tomography measurement of hepatic steatosis: prevalence of hepatic steatosis in a Canadian population. Can J Gastroenterol Hepatol 2016:4930987. https://doi.org/10.1155/2016/4930987
  14. Yeh, B., Liu, P., Soto, J., Corvera, C., Hussain, H. (2009) MR imaging and CT of the biliary tract. Radiographics 29:1669–1688. https://doi.org/10.1148/rg.296095514

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