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- Topic: Liver Pathology.
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- Diffuse Disease: Hepatocytes are the parenchymal liver cells responsible for liver function; diffuse hepatocellular disease affects hepatocytes and liver function.
- Measurement: hepatic enzyme levels rise with hepatocyte necrosis.
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- Major diffuse disease types: Fatty liver infiltration; Hepatitis (acute and chronic); Cirrhosis (acute and chronic).
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- Fatty Infiltration (steatosis): reversible accumulation of triglycerides in hepatocytes; reflects major liver injury or systemic metabolic disorder.
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- Causes of fatty liver: Obesity; Excessive alcohol; Poorly controlled hyperlipidemia; Diabetes; Excess corticosteroids; Pregnancy; Total parenteral nutrition; Severe hepatitis; Glycogen storage disease; Cystic fibrosis; Pharmaceutical.
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- Imaging correlation: fatty infiltration often shows increased hepatic echogenicity on ultrasound.
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- Focal Fatty Infiltration and Focal Fatty Sparing: focal normal-appearing regions within fatty liver; sparing commonly near the gallbladder, porta hepatis, caudate lobe, and liver margins.
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- Focal fatty sparing: imaging feature where pockets of normal liver tissue appear within fatty infiltration (e.g., near gallbladder).
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- Hepatitis: diffuse inflammatory and infectious disease of the liver; can be viral, bacterial, fungal, or parasitic.
- Causes include local infection (viral hepatitis), systemic infection (e.g., mono, amebiasis), or drug/toxic injury.
- Inflammation impairs hepatocyte function; necrosis may obstruct blood/bile flow; may elevate ALT, AST, conjugated and unconjugated bilirubin.
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- Viral Hepatitis: common hepatotropic viruses HAV, HBV, HCV.
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- Hepatitis A: fecal-oral spread; worldwide; endemic in developing countries; acute infection with possible recovery or death from acute liver failure.
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- Hepatitis B: bloodborne; spread by infected blood/plasma, needles; risk to healthcare workers; also present in body fluids; sexual transmission possible.
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- Hepatitis C: diagnosed by anti-HCV antibody; transmission through blood/body fluids; often via needle sharing or sexual contact.
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- In the US, approximately 60\% of acute viral hepatitis is type B, 20\% type A, and 20\% other types; initial symptoms may be flu-like; viral hepatitis can be fatal or progress to chronic disease including cirrhosis or HCC.
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- Acute Hepatitis: most recover within about 4\text{ months} without complications.
- Complications range from mild disease to massive necrosis and liver failure.
- Pathology: hepatocyte injury with swelling/degeneration, Kupffer cell/enlargement, and regeneration.
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- Ultrasound in Acute Hepatitis: liver texture may be normal or portal borders more prominent; may show a Starry Night (Van Gogh) appearance; slightly increased echogenicity; possible attenuation; hepatosplenomegaly; thickened gallbladder wall.
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- Chronic Hepatitis: defined as hepatic inflammation extending beyond 6\text{ months}; causes include viral, metabolic, autoimmune, or drug-induced.
- Chronic active hepatitis shows inflammation across the limiting plate with perilobular distribution and piecemeal necrosis, often with fibrosis.
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- Chronic Hepatitis: symptoms may include nausea, anorexia, weight loss, tremors, jaundice, dark urine, fatigue, varicosities; chronic persistent hepatitis is benign and self-limiting; chronic active hepatitis often progresses to cirrhosis and liver failure.
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- Ultrasound in Chronic Hepatitis: liver parenchyma is coarse with decreased brightness of the portal triads; attenuation not as great as in fatty infiltration; liver may not enlarge; fibrosis may cause soft posterior shadowing.
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- Cirrhosis: chronic degenerative liver disease with fibrous tissue covering lobes; parenchyma degenerates; lobules infiltrated with fat; hallmark is simultaneous parenchymal necrosis, regeneration, and diffuse fibrosis leading to disorganized lobular architecture.
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- Causes of cirrhosis: #1 cause is Hepatitis C; alcoholic liver disease; NAFLD; NASH; Hepatitis B; others include hemochromatosis (iron deposition) and Wilson disease (copper deposition).
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- Cirrhosis types: Micronodular (often from chronic alcohol use) and macronodular (often from chronic viral hepatitis or infection).
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- Cirrhosis clinical features: acute or asymptomatic; nausea, flatulence, ascites, pale stools, weakness, abdominal pain, varicosities, spider angiomata; classic signs: hepatomegaly, jaundice, ascites; progression to liver failure and portal hypertension.
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- Cirrhosis progression on ultrasound: Early — hepatomegaly with increased echogenicity and coarse texture; mid — coarse texture, nodular borders, lobe atrophy, ascites; late — coarse echotexture, hyperechoic liver, small size, nodular borders, possible nodules, ascites, portal hypertension.
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- Cirrhosis ultrasound snapshot notes: early cirrhosis may show hepatomegaly and reduced vasculature; late cirrhosis shows shrunken liver with ascites and thick gallbladder wall.
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- Glycogen Storage Disease (GSD): six categories based on symptoms and enzymatic defects; Type I (von Gierke) is the most common; inherited glycogen storage disease with excess glycogen deposition in liver and kidneys.
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- GSD imaging: von Gierke disease may show hepatomegaly, increased echogenicity, and hepatic adenomas (round, homogeneous); large adenomas may be inhomogeneous.
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- Hemochromatosis: iron overload with deposition throughout body; can lead to cirrhosis and portal hypertension; ultrasound: hepatomegaly, cirrhotic changes, and increased echogenicity of liver parenchyma.
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- Hepatic Vascular Flow Abnormalities: vascular flow changes can be seen; reference to online resource for views.
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- Diffuse Abnormalities of the Liver Parenchyma: Biliary obstruction; common duct stones and stricture; extrahepatic mass; passive hepatic congestion.
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- Biliary Obstruction (proximal to cystic duct): causes include gallstones, common bile duct carcinoma, porta hepatis metastasis; clinical: jaundice and pruritus; labs: direct bilirubin and alkaline phosphatase elevated.
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- (Imaging slide; content not reproduced here.)
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- Biliary Obstruction (distal): causes include stones in the common duct, extrahepatic porta hepatis mass, common duct stricture; clinical: RUQ pain, jaundice, pruritus; labs: direct bilirubin and alkaline phosphatase elevated.
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- Distal obstruction example: dilated common duct due to stones or mass; sagittal scans illustrate dilatation.
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- Diffuse abnormalities: extrahepatic mass at porta hepatis can mimic biliary obstruction; common duct stricture (post-cholecystectomy) shows direct bilirubin and ALP elevation; passive hepatic congestion from congestive heart failure with hepatomegaly and mild LFT elevation.
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- Focal Hepatic Disease: benign cysts; prevalence and associations; simple hepatic cysts are well-demarcated, thin-walled, anechoic with posterior acoustic enhancement.
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- Polycystic Liver Disease: autosomal dominant; ~1 in 500; 50-74% of patients with polycystic kidney disease have hepatic cysts; usually small (<2 ext{–}3 ext{ cm}) and multiple; may enlarge and cause biliary obstruction at the porta hepatis.
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- Focal Inflammatory Disease of the Liver: hepatic abscesses due to biliary tract disease, surgery, or trauma; fever, leukocytosis, RUQ pain; US look for solitary/multiple lesions and fluid collections in Morison's pouch or subphrenic/subhepatic spaces.
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- Pyogenic (Bacterial) Abscess: accounts for approximately 80\% of hepatic abscesses; routes include biliary disease (most common), portal vein, hepatic artery, and direct extension; sources include cholangitis, appendicitis/diverticulitis, inflammatory disease, colitis; trauma or infarction after embolization may also occur.
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- Amebic Abscess: Entamoeba histolytica; parasites reach liver via portal vein; associated with travelers/immigrants; typically presents with GI symptoms; cysts ingested lead to liver involvement.
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- Amebiasis: ingestion of cysts in contaminated water/food; organism usually affects colon/cecum; can travel to liver via portal venous system; symptoms range from asymptomatic to abdominal pain/diarrhea.
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- Amebic abscess gross pathology: cavitary lesion with yellow necrotic material; usually no purulent pus.
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- Sonographic findings and clinical context: abnormal liver function tests with RUQ pain; diffuse fibrosis and echogenic bands along intrahepatic portal vein; portal hypertension signs; schistosomiasis considered in differential.
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- Echinococcal cyst (Hydatid disease): infectious cystic liver disease; caused by Echinococcus (dog-sheep cycle); water-lily sign and daughter cysts can be seen; complex cystic mass in liver.
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- Echinococcal cyst imaging: right lobe complex mass with fluid and debris; water-lily sign.
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- Fungal Abscess (Candidiasis): patterns described as wheel within a wheel or bull's-eye; uniformly hypoechoic focus with internal echoes.
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- Hepatic Candidiasis: occurs in immunocompromised hosts (chemotherapy, transplant, HIV); fungus may disseminate; ultrasound shows wheel-within-a-wheel or bull's-eye patterns; often hypoechoic focus.
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- Pneumocystis Carinii: opportunistic infection in AIDS and immunocompromised patients; sonographic patterns range from diffuse tiny nonshadowing foci to extensive parenchymal replacement by calcified echogenic clumps.
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- Chronic Granulomatous Disease: congenital defect of phagocytes; susceptibility to infections; imaging may show poorly marginated hypoechoic mass with posterior enhancement; calcifications possible; aspiration needed for diagnosis.
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- Benign Hepatic Tumors: Cavernous Hemangioma: most common benign liver tumor; more common in women; often asymptomatic; may bleed in a minority.
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- Cavernous Hemangioma imaging: irregular, echogenic due to vascular content; typically benign appearance.
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- Liver Cell Adenoma: more common in women; linked to oral contraceptives; RUQ pain from rupture/bleeding; increased in patients with type I glycogen storage disease or von Gierke; surgical resection due to risk of malignant transformation.
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- Ultrasound artifact: speed artifact (media with different sound speeds can cause artifact).
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- Focal Nodular Hyperplasia (FNH): second most common benign liver mass; occurs in women < 40\text{ years}; likely from developmental hyperplastic lesions related to congenital vascular formation; patient usually asymptomatic; occurs more in the right lobe.
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- FNH characteristics: typically a single, well-circumscribed lesion ("stealth lesion"); often subcapsular or pedunculated; central fibrous scar; composed of normal hepatocytes, Kupffer cells, bile ducts, and fibrous tissue; nodules separated by fibrous bands; may have increased bleeding tendency within tumors.
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- Hepatocellular Carcinoma (HCC): most common primary malignant liver tumor; more often arises in livers with cirrhosis or chronic hepatitis B/C; more common in men.
- Presentation: history of cirrhosis/hepatitis B/C, palpable mass, hepatomegaly, anorexia, fever.
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- HCC risk factors (summary): Hepatitis C; Alcoholic liver disease; NAFLD; NASH; Hepatitis B; others include Hemochromatosis and Wilson disease; cirrhosis is a related condition.
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- HCC presentation patterns: solitary massive tumor; multiple nodules; diffuse infiltrative masses.
- Pathology: focal lesion; invasive lesion with necrosis/hemorrhage; poorly defined lesion.
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- HCC invasion: can invade hepatic veins causing Budd-Chiari syndrome; portal venous system may be invaded by tumor or thrombosis; can destroy portal venous radicle walls.
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- HCC gross pathology: cirrhotic liver with solitary malignant nodule; large tumor may be poorly demarcated from liver.
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- Metastatic Disease: most common form of liver neoplasm; primary sites include colon, breast, and lung; prognosis varies by primary site; generally poorer than many benign processes when detected late.
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- Metastatic Disease: spread to liver via lymphatics or bloodstream (portal vein/hepatic artery); often multiple nodules.
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- Metastatic Disease on ultrasound: multiple well-defined iso-, hyper-, or hypoechoic lesions; necrosis common in nodules.
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- Video reference: What is Mets? (online resource).
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- Hepatoblastoma: most common malignant liver tumor in infants/children; usually before age 2; presents as enlarged asymptomatic abdominal mass; associations with Beckwith-Wiedemann syndrome and FAP; elevated AFP; may have lung metastases and portal vein invasion.
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- Infantile Hepatic Hemangiomas (Hepangioendotheliomas): benign vascular tumors in neonates/early months; rapid growth; ultrasound shows hepatomegaly and high vascularity; may cause congestive heart failure; often spontaneously regress by 12 ext{–}18\text{ months}.
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- Lymphoma: malignant lymphocyte proliferation; may cause hepatomegaly with normal or diffusely altered parenchymal echoes; symptoms include enlarged lymph nodes, fever, night sweats, weight loss; splenomegaly or retroperitoneal nodes support diagnosis.
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- Lymphoma (continued): focal hypoechoic masses may be seen; clinical signs help differentiation.
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- Elastography: measures tissue stiffness; malignant lesions are stiffer; overall liver stiffness indicates fibrosis or cirrhosis; useful to identify minimal fibrosis and assess severe fibrosis or cirrhosis.
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- Liver Biopsy with ultrasound: ultrasound-guided biopsy is a common technique to obtain liver tissue.
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- Hepatic Trauma: liver is the third most commonly injured abdominal organ; laceration occurs in about 3\% of trauma patients; right lobe more often affected; injury severity ranges from small laceration to subcapsular hematoma or capsular disruption; treatment decisions depend on laceration size, hemoperitoneum, and patient status.
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- End of notes.