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Abdomen (LIVER (Malignant tumors (Hepatocellular Carcinoma (most common…

- - - - the most common benign liver TUMORS
        
        common in females
        
        Asymptomatic
      - CT morphology
        
        Can be multiple in 50 %,
        
        On noncontrast CT usually a well-defined hypodense lesion with lobulated borders,
        
        A subcapsular location is typical,
        
        In the arterial phase, there is typically globular peripheral enhancement
        
        By the end of the portal phase all enhancing lacunae are isoattenuating to the hepatic vessels (blood-pool effect)
        
        Enhancement of very large tumors is often heterogeneous because of the presence of thrombosed or necrotic areas
        
        Small hemangiomas often show atypical features such as homogenous hyperattenuation or hypoattenuation during the arterial phase
    - - The second commonest benign liver TUMOR.
        
        20-50 years of age
        
        more in women
        
        Usually solitary, can be multiple in 20 %
        
        Most lesions are located in the periphery of the liver and measure < 5 cm
        
        A central scar is pathognomonic and can be visualized in up to 50% cases
      - CT morphology
        
        NO CAPSULE
        
        calcifications are rare (< 1%)
        
        On non-contrast are well-defined, slightly hypoattenuating or isoattenuating
        
        Arterial phase CT demonstrates intense, usually homogenous enhancement of the entire tumor
  - - - The commonest tumors with hepatic metastases are: Carcinomas of the colon (approximately 40%), Stomach (>20%), Pancreas (20%), Breast (approximately 10%), Lung (approximately 10%)
      - CT morphology
        
        On unenhanced CT most metastases are hypoattenuating to the liver parenchyma
        
        Small lesions are nodular and homogenous
        
        Larger lesions are more irregular, heterogenous
        
        Calcifications are common in mucinous GI tract carcinoma and in chemotherapeutically treated hypervascular lesions (e.g., carcinoid)
        
        After contrast administration metastases from hypovascular tumors have an enhancing rim that can be seen during the arterial phase
        
        Hypervascular metastases show moderate to intense enhancement during the arterial phase that may persist in the portal phase
        
        Cystic metastases – e.g. from ovarian carcinoma
    - - most common primary hepatic tumor
        
        common in Male
        
        Peak occurrence is in the fifth to seventh decades
        
        Hepatic cirrhosis is the greatest risk factor
      - On unenhanced CT: solitary or multiple hypo- to isoattenuating masses
        
        Calcifications are is seen in 5-10% of cases
        
        Areas of necrosis or fatty metamorphosis appear as hypoattenuating foci
        
        nodular types are sharply demarcated from the liver,
        
        the infiltrative types are often heterogenous with ill-defined margins
        
        In hypervascular tumors arterial phase CT demonstrated intense enhancement
        
        larger tumors often are heterogenous due to necrosis and hemorrhage
      - During the portal venous phase HCCs wash out rapidly and become isodense to hypodense, relative to normal liver
        
        On delayed phase images the capsule and fibrous septa are relatively hyperattenuating and show prolonged enhancement while the tumor are iso- to hypoattenuating to the liver
    - - Most common form of liver cancer in children
        
        Children from infancy to about 5 years old (90% younger than 3 y.o)
        
        Black children (boys)> white children
        
        CT:
        Well defined heterogeneous mass with hypoattenuating compared to surrounding liver
        areas of necrosis and haemorrhage
        30- 50% calcification, 20 % multifocal
    - - Is the common endpoint of a variety of chronic liver diseases which cause hepatocellular necrosis
        
        A typical distribution of causality in Western populations:
        Alcohol (60-70%), Viral hepatitis (10%)
        
        Can be diagnosed with US, CT, MRI
        
        US/CT:
        Surface and parenchymal nodularity, Fatty change, Segmental atrophy (VI and VII), Signs of portal hypertension: Portal vein enlargement & Portal vein thrombosis.
  - - - Hepatomegaly is common and is associated with rounding of the liver contours (most apparent in the left liver lobe)
        
        In normal liver, the hepatic vessels are hypoattenuating relative to the liver parenchyma
        
        In the fatty liver, the hepatic vessels become isoattenuating to the surrounding liver
        
        Another indicator is the enhancement difference between liver and spleen on portal phase scans (more than 20 HU lower than spleen)
- - - - most commonly seen in patients with advanced primary tumors
        
        The most frequent primaries are malignant melanoma, breast carcinoma and bronchial carcinoma
        
        Metastases may appear as ill-defined areas of low attenuation on NCT scans
        
        They are more clearly delineated after contrast administration
        
        Cystic areas of necrosis may occur
        
        Multifocal lesions are the rule
    - - the commonest primary malignancy of the spleen
        
        Primary splenic lymphoma is rare (1-2% of all lymphomas) and is usually a non-Hodgkin lymphoma
        
        Secondary splenic involvement is frequent in both Hodgkin’s disease (approximately 25-33% of all patients are affected)
      - CT/MR morphology
        
        Splenic involvement in lymphoma can have four forms: homogenous enlargement, miliary nodules, multifocal lesions of 1 to 10 cm, or a solitary mass
        
        CT can detect focal or multifocal disease more reliably than diffuse infiltration
        
        Larger focal lesions may cause bulging of the splenic contour
        
        During parenchymal phase of enhancement focal lesions are clearly demarcated as hypodense areas
- - - - variable in their size and location
        
        They may be completely intrapancreatic, but it is more common to find extrapancreatic lesions located in the omental bursa or along Gerota’s fascia
        
        Calcifications may be visible in the cyst wall
        
        CT numbers of the fluid of more than 25HU are indicative of coexisting fat necrosis, bleeding or infection
        
        The presence of gas bubbles within a pseudocyst may be caused by gas-forming bacteria
  - - - Up to 90% are adenocarcinomas
        
        Most (80%) occur in the pancreatic head
        
        Tumors in the body (15%) or tail of the pancreas (5%) do not cause typical symptoms and usually are not diagnosed until they have reached an inoperable stage
        
        The only effective treatment of pancreatic carcinoma is surgical resection
        
        early lymphogenous and hematogenous spread
        
        a small percentage of pancreatic cancers are resectable at the time of diagnosis (10-30%)
        
        Vascular invasion is a relative criterion for the lack of resectability
      - CT morphology
        
        PC are almost always isoattenuating to the parenchyma on unenhanced CT scans
        
        On contrast enhanced scans adenocarcinoma demarcates as a hypoattenuating mass from the normal parenchyma
      - Dilatation of the pancreatic duct is suggestive of a tumor but may be also seen in chronic pancreatitis
        
        Signs strongly suggestive of a tumor are an abrupt cutoff of the duct or dilatation of the duct in the pancreatic body and tail with a normal caliber in the pancreatic head
        
        A concomitant obstruction of the intrapancreatic portion of the common bile duct with no evidence of a stone may be cased by a carcinoma in the pancreatic head
  - - - The predominant macroscopic feature of mild acute pancreatitis is edema with minimal organ dysfunction
        
        Necrosis of peripancreatic adipose tissue is common
        
        Severe acute pancreatitis is characterized by extensive changes of the peripancreatic fat and hemorrhagic fluid within the retroperitoneal space
        
        high mortality rate
      - CT morphology
        
        The edematous areas appear slightly enlarged and show decreased attenuation
        
        The margins of the gland are blurred
        
        Post contrast scans usually show slightly inhomogeneous enhancement of the parenchyma with no perfusion defects
        
        In severe acute pancreatitis the gland is enlarged, nonhomogeneous, and poorly demarcated from surrounding tissue
        
        Necrotic areas in the pancreas appear hypoattenuating,
        
        Hemorrhagic areas are hyperattenuating
        
        Intravenous contrast should be used to determine the extend of pancreatic necrosis: viable parenchyma shows contrast enhancement while necrotic parenchyma does not
      - Complications
        
        Pseudocyst formation, Infection, Hemorrhage, Formation of pseudoaneurysms, Venous thrombosis
    - - the most commonly the result of alcohol abuse or biliary disease
        
        Patients with pancreatic calcifications show an increased incidence of pancreas carcinoma
      - CT morphology
        
        CT findings are normal in 10% of patients with clinically diagnosed chronic pancreatitis
        
        The inflammation may lead to focal or diffuse enlargement of the pancreas but more frequently the gland is atrophic
        
        Calcifications are more common in the alcohol-related form (50%) than in the biliary form (approximately 20%)
        
        Pseudocyst are found in approximately 30% of cases and an intra- or extrapancreatic location
        
        Ductal calcifications occur in up to 90% of patients with severe and in up to 55% of patients with only mild to moderate pancreatitis
        
        Widening of the pancreatic duct to more than 4 mm is found in more than 50% of patients
        
        The duct is more often irregular
      - complications
        
        pleural effusion, Pancreatic pseudocysts, ascites, DM, classification, stones in pancreatic duct, steatorrhea, decrease vit. k metabolism
- - - - Stones are visible on unenhanced scans only if their CT attenuation significantly differs from the surrounding bile (0-20HU)
        
        Cholesterol stones range from slightly hypoattenuating (pure cholesterol) to hyperattenuating (containing calcium)
        
        Pigment stones (calcium bilirubinate) are hyperattenuating
        
        Gas-containing stones result from dehydration and cavitation (Mercedes-Benz sign)
  - - - extrahepatic cholangiocarcinoma is more common than intrahepatic
        
        The cardinal symptom is pain and jaundice
        
        The bifurcation of the hepatic duct is affected in 10 to 25% of cases (Klatskin’s tumor) and more than 50% tumors arise in the common bile tract
      - The tumor spreads via the lymphatics, metastasizing to the hepatoduodenal ligament and the celiac lymph nodes
        
        Hepatic infiltration occurs in more than 20% of cases and peritoneal carcinomatosis in less than 10%
      - CT morphology
        
        Isolated dilatation of the intrahepatic bile ducts is the most important sign
        
        Only about 40% of tumors can be directly visualized at the site of the obstruction
    - - Carcinoma of the gallbladder is the commonest malignant tumor of the biliary system
        
        more common in women
        
        The risk is increased in patients with:
        porcelain gallbladder (10-20% incidence), chronic cholecystitis, inflammatory bowel disease, familiar polyposis
      - More than 75% of gallbladder carcinomas spread beyond the gallbladder or metastasize to regional lymph nodes
        
        The tumor most commonly invade the liver (>50%), duodenum (>10%), and colon (approximately 10%)
        
        Regional lymph node metastasis (hepatoduodenal ligament, peripancreatic nodes, periportal nodes) occurs in more than 5% of cases
      - CT morphology
        
        CT usually shows a hypoattenuating mass in the gallbladder bed infiltrating the fatty tissue and liver
        
        The tumor in early stages may be marked by asymmetric focal thickening of the gallbladder wall or polypoid intraluminal mass
        
        Tumor demarcation from the lumen is seen most clearly during the late phase after contrast administration