Fungal and Abscess Infections in the Liver

Fungal Infection/ Abscess Candidiasis

• Mycotic (fungal) infection of the blood resulting in small abscesses in the liver
• Lesion appearance changes over time
• "Wheel within a wheel" is the earliest stage:
  • Peripheral hypoechoic zone
  • Inner echogenic wheel
  • Hypoechoic center
• Outer hypoechoic wheel is fibrosis surrounding the inner echogenic wheel of inflammatory cells and a central hypoechoic area of necrosis
• "Bull's eye" lesion appears when the hypoechoic center calcifies
• "Uniformly hypoechoic focus" is the most common presentation, may resemble metastasis
• "Echogenic focus" is calcification, a scar formation seen in the late stage of the disease

Cavernous Hemangiomas

• Most common benign liver tumor
• Found in approximately 4% of the general population

Pyogenic Abscess

• Pus-containing lesion
• 80% of cases caused by Escherichia coli
• Biliary tract is the most common source
• Pyogenic bacteria enters via the portal vein or hepatic artery
• Right lobe is more commonly affected
• Sonographic findings:
  • Complex mass with irregular walls
  • Gas
  • Reverberation artifact
• Symptoms:
  • Right upper quadrant pain
  • Leukocytosis
  • Fever
  • Elevated liver function tests (LFTs)
• Aspiration is necessary to confirm diagnosis

Amebic Liver Abscess

• Occurs when parasite reaches the liver, typically via the portal vein
• Usually contracted from consuming contaminated food and water
• Most common extraintestinal complication of amoebic dysentery
• Occurs almost exclusively in immigrants or travelers
• Most often involves the gastrointestinal tract
• Symptoms usually appear 8-12 weeks after travel
• Symptoms and findings:
  • Right upper quadrant pain
  • Hepatomegaly
  • Diarrhea
  • Fever
  • Leukocytosis
  • Elevated LFTs
• Sonographic findings:
  • Round, hypoechoic/complex mass
  • Usually found in the right lobe of the liver, near the dome
  • Continuous with the liver capsule
  • Acoustic enhancement
• Aspiration may be necessary for diagnosis

Schistosomiasis

• One of the most common parasitic infections in humans
• Contaminated water with immature worms can penetrate skin and travel via lymphatics and bloodstream to the mesenteric veins
• Common in Africa, Asia, Indonesia, China, Japan, South America, and the Mediterranean

Metastatic Disease

• After lymph nodes, the liver is the most common site for metastases from cancers arising in other areas
• Metastatic liver tumors are 18-20 times more common than hepatocellular carcinoma (HCC)
• Most common primary cancers contributing to metastatic liver disease:
  • Gallbladder
  • Colon
  • Stomach
  • Pancreas
  • Kidney
  • Ovaries
  • Breast
  • Lung

L

iver is vulnerable to metastases due to its large blood volume and ample lymphatic drainage

• Approximately 40% of patients with cancer have liver metastases
• Easily established in the liver due to its dual blood supply and factors promoting cell growth
• Lab values:
  • LFT values may be normal
  • AST and ALT may be elevated
  • ALP and bilirubin elevated with biliary obstruction
  • AFP is typically not elevated in liver metastatic disease
• Sonographic findings:
  • Hyperechoic metastases - gastrointestinal tract
  • Hypoechoic metastases - lymphoma
  • Bulls eye or Target metastases - lung
  • Calcified metastases - mucinous adenocarcinoma of the colon
  • Cystic metastases - leiomyosarcoma
• Ultrasound-guided biopsy is needed to determine the primary tissue diagnosis due to nonspecific sonographic appearance of metastases

Gallbladder

• Function is to store and transport bile from the liver to the gastrointestinal system
• The biliary system comprises the gallbladder and the hepatic ducts

Mirizzi Syndrome

• Extrahepatic biliary obstruction due to an impacted stone at the cystic duct causing extrinsic mechanical compression of the common hepatic duct
• Associated findings:
  • Intrahepatic duct dilatation
  • Cystic duct stone
  • Curved segmental stenosis of the common hepatic duct
  • Cholecystocholedochal fistula

Cholangiocarcinoma (bile duct carcinoma)

• Bile duct adenocarcinoma - originates within extrahepatic bile ducts (common hepatic duct or common bile duct)
• Klatskin tumor - cholangiocarcinoma located at the hepatic hilum (junction of the right and left hepatic duct) resulting in intrahepatic but not extrahepatic biliary dilation
• Occurs equally in men and women between the age 50-70
• Most common predisposing condition is primary sclerosing cholangitis
• Most common finding - intrahepatic duct dilatation
• Symptoms:
  • Jaundice
  • Weight loss
  • Abdominal pain
• Labs:
  • Increased serum bilirubin
  • Increased ALP

Cholangitis

• Inflammation of the biliary tree
• May result in cirrhosis, portal hypertension, and sepsis
• Sonographic: bile duct wall thickening
• Labs:
  • Increased conjugated bilirubin
  • ALP
  • GGT
  • Amylase and Lipase
  • Leukocytosis
• "Charcot Triad"
  • Right upper quadrant pain
  • Fever
  • Jaundice
• Causes:
  • Choledocholithiasis (most common)
  • ERCP
  • Obstructive tumors
    • Pancreatic cancer
    • Cholangiocarcinoma
    • Ampullary cancer

Primary Sclerosing Cholangitis

• Sonographic:
  • Common bile duct wall thickening
  • Thickened walls cause dilatation (stellate pattern) of intrahepatic ducts

Right Subphrenic Space (AKA Suprahepatic Space)

• An extension of the greater sac between the right hemidiaphragm and anterior superior liver, rightward of the falciform ligament

Hepatorenal Space (AKA Morrison Pouch)

• Created by peritoneum, reflecting from the liver over the right kidney and right posterior peritoneal wall
• When the patient is in the supine position, this space is the most gravity-dependent potential space of the abdominal cavity, collecting fluid from the supracolic area and lesser sac

Lesser Sac/Omental Bursa

• Sandwiched between the posterior stomach and parietal peritoneum covering the anterior pancreas (front-to-back) and splenorenal and gastrosplenic ligaments and epiploic foramen (omental foramen, foramen of Winslow) (side-to-side)
• In cases of posterior gastric wall perforation, inflammation, or trauma to the pancreas, fluid or a pseudocyst may be identified in this space.

Right Anterior Subphrenic Space and Hepatorenal Space

• Fluid within the right anterior subphrenic space and ascites within the hepatorenal space may be seen on longitudinal imaging of the right upper quadrant

Lesser Sac (Omental Bursa)

• Hematoma within the lesser sac may be seen on a transverse image of the epigastrium in patients with acute pancreatitis
• The posterior wall of the stomach borders the hematoma anteriorly and the pancreas forms the posterior border

Right & Left Paracolic Gutters

• Grooves found along the lateral ascending and descending colon that conduct fluids between the supracolic compartment of the abdomen and infracolic compartment of the inferior abdomen and pelvis
• Important in determining the extension of a disease process
• Arrows indicate where free fluid could collect within the left paricolic gutter on a transverse image

Vesicorectal Space (AKA Cul-de-sac in male)

• Created by peritoneal reflection over the rectum and posterior bladder wall
• When the male is in a supine position, this space is the most gravity-dependent potential space of the pelvic cavity, draining fluid from the infracolic area.

Rectouterine Space

• AKA - Rectovaginal Pouch, Pouch of Douglas, Posterior Cul-de-sac in female
• Created by parietal peritoneum draping over the anterior rectum, posterior vaginal wall, and posterior uterus