THE LIVER Methods of examination 1. US 2. CT 3. MRI 4. Nuclear medicine

1. THE LIVER Methods of examination 1. US 2. CT 3. MRI 4. Nuclear medicine

3. CIRRHOSIS Pathologically cirrhosis consists of varying amounts of hepatic necrosis, fibrosis, fatty infiltration and nodular regeneration Types: 1.Chronic sclerosing cirrhosis – minimal regenerative activity of hepatocytes, little nodule formation, liver is hard and small. 2. Nodular cirrhosis – regenerative activity with presence of many small nodules; initially the liver may be enlarged. Causes – alcohol, hepatitis B, hemochromatosis

4. Radiographic features Liver - Small liver, increased echogenicity, heterogeneous - Nodular surface - Regenerating nodules – hypoechoic - Unequal distribution of cirrhosis in different segments – left lobe appears larger than right lobe; lateral segment of left lobe enlarges, medial segment shrinks; ratio of the width of the caudate lobe to the right hepatic lobe is 0,6 Portal hypertension - Collaterals – left gastric, paraesophageal, mesenteric, splenorenal - Splenomegaly - Ascites Complications – hepatocellular carcinoma, esophageal varices with bleeding

7. FATTY LIVER Causes – obesity, alcohol, hyperalimentation, debilitation, chemotherapy, steroids Radiographic findings US – fat increases liver echogenicity, renal cortex appears more hypointense relative to liver than normal, intrahepatic vessel borders become indistinct or cannot be visualized, nonvisualization of diaphragm CT – fatty areas are hypodense, hepatic and portal veins appear dense because of decreased parenchymal density

9. PYOGENIC ABSCESS Pathogens – Escherichia Coli,aerobic streptococci, anaerobes Causes – ascending cholangitis, trauma, surgery, portal phlebitis. Radiographic features - CT – hypodense with peripheral enhancement, no fill-in. - Double target sign – wall enhancement with surrounding hypodense zone. - 30% contain gas. - any abscess can be drained percutaneously, particularly: deep abscesses, no response to treatment, nonsurgical candidates.

11. HYDATID DISEASE Humans are intermediate hosts of the dog tapeworm (taenia echinococcus). Two forms: E.granulosus – more common, few large cysts E.multilocularis – less common, more invasive Radiographic features E.granulosus - well-delineated cysts - size of cysts usually very large - daughter cysts within larger cysts ( multiseptated cysts) are pathognomonic - rimlike cyst calcification - double rim sign: pericyst, endocyst - enhancement of cyst wall

12. E.multilocularis • - poorly marginated, multiple, hypodense liver lesions. • - lesions are infiltrative (chronic granulomatous reaction with necrosis, cavitation). • calcifications are punctate and dystrophic, not rimlike. • Complications • - rupture into peritoneal, pleural, pericardial cavity • - obstructive jaundice due to external compression or intrinsic obstruction of biliary tree

17. HEMANGIOMA - Frequency – 4-7% of population, 80% in females.Hemangiomas may enlarge particularly during pregnancy or estrogen administration. US - hyperechoic lesions 80%. - hypoechoic lesions especially in fatty liver. - giant hemangiomas are heterogeneous. - anechoic peripheral vessels may be demonstrated by color Doppler . CT - hypodense, well-circumscribed lesion on precontrast scan globular or nodular intense enhancement. MRI - hyperintense on heavily T2W sequences. - imaging modality of choice. Nuclear imaging (SPECT) - decreased activity on early dynamic images. - increased activity on delayed blood pool images.

19. HEPATOCELLULAR CARCINOMA (HCC) Risk factors – cirrhosis, chronic hepatitis B, hepatotoxins, metabolic disease in paediatric patients Radiographic features General - three forms – solitary, multiple, diffuse - portal and hepatic vein invasion is common - metastases – lung, adrenal, lymph nodes, bone

20. CT • - hypodense mass lesion • - early arterial enhancement • Pseudocapsule • US • - most small HCC are hypoechoic • - larger HCC are heterogeneous • high-velocity Doppler pattern • Angiography • - hypervascular • - AV shunting is typical • - Dilated arterial supply

23. METASTASES 30% of patients who die of malignancy have liver metastases. Colorectal carcinoma, stomach, pancreas, breast, lung Sensitivity for lesion detection: CTAP – high-dose delayed CT – CECT,MRI – US - Echogenic MTS – GI malignancy, HCC, vascular - Hypoechoic MTS – lymphoma, bull’s eye pattern (hypoechoic halo around lesion) - Calcified metastases – all mucinous metastases – colon, thyroid, ovary, kidney, stomach - Cystic metastases – necrotic leyomiosarcoma

25. PORTAL HYPERTENSION Criteria – hepatic wedge pressure  10 mm Hg. Causes: Presinusoidal Extrahepatic (obstruction of portal vein) – thrombosis, compression Intrahepatic (obstruction of portal venules) – hepatic fibrosis, infection Sinusoidal Cirrhosis ,sclerosing cholangitis Postsinusoidal Budd-Chiari syndrome, congestive heart failure Radiographic features - Portal vein diameter  13 mm - Collateral vessels – gastroesophageal varices via coronary vein, azygos; SMV collateral – mesenteric varices; splenorenal varices; IMV collateral – hemorrhoids - Splenomegaly - Ascites

26. THE BILIARY SYSTEM • Methods of examination • Abdominal plain film – gas or calcium in the biliary tract • US • CT • MRI + MRCP • ERCP • PTC • Scintigraphy

32. ACUTE CHOLECYSTITIS Causes - gallstone 95% US - Luminal distension  4cm - Wall thickening  5 mm (edema, congestion) - Gallstones - Pericholecystic fluid Complications - Gangrenous cholecystitis: rupture of GB - Emphysematous cholecystitis - Empyema

34. CHRONIC CHOLECYSTITIS - GB wall thickening (fibrosis, chronic inflammation) - Gallstones - Failure of GB to contract

35. CHOLELITIASIS Types: Cholesterol stones are caused by precipitation of supersaturated bile - Pigment stones – precipitate of calcium bilirubinate - Mixed stones Predisposing factors: - Obesity - Hemolytic anemia - Abnormal enterohepatic circulation of bile salts - Diabetes - Cirrhosis - Hyperparathyroidism US – method of choice – hyperreflective image with prominent posterior shadow; mobility of stones (exception – stones impacted in neck or stones adherent to wall)

38. CHOLANGIOCARCINOMA Adenocarcinoma of the biliary tree. Clinical – jaundice, pruritus, weight loss. Treatment – pancreaticoduodenectomy or palliative procedures ( stent placement, biliary bypass) Location – hilar (originates from epithelium of main hepatic ducts or junction –Klatskin tumor) + peripheral – originates from epithelium of intralobular ducts Radiographic features - Dilated intrahepatic ducts - Hilar lesions – central obstruction + lesions are usually infiltrative so that a mass is not usually apparent + encasement of portal veins causes irregular enhancement by CT - Peripheral lesions – may present as a focal mass or be diffusely infiltrative + retain contrast materials on delayed scans + occasionally invade veins - ERCP very useful

41. THE PANCREAS • Methods of examination • CT • US • MRI + MRCP • Arteriography

42. PANCREATITIS Classification - Mild acute pancreatitis (interstitial edema) - Severe acute pancreatitis (necrosis, fluid collections) - Chronic pancreatitis Causes - Alcohol - Cholelitiasis - Abdominal trauma - Hyperlipidemia, hypercalcemia - Drugs – azathioprine, sulfonamides - Peptic ulcer - Pregnancy

43. Imaging – CT staging Grade A – normal pancreatic appearance Grade B – focal or diffuse enlargement of pancreas Grade C – pancreatic abnormalities and peripancreatic inflammation Grade D – 1 peripancreatic fluid collection Grade E – 2 peripancreatic fluid collections and/or gas Complications - Necrosis - Acute fluid collections – enzyme-rich pancreatic fluid, no fibrous capsule - Pseudocyst – encapsulated collection of pancreatic fluid - Abscess - Hemorrhage

45. CHRONIC PANCREATITIS Progressive, irreversible destruction of pancreatic parenchyma by repeated episodes of mild or subclinical pancreatitis. Radiographic features Commonly small, atrophic pancreas Fatty replacement, fibrosis, calcifications Irregular dilatation of pancreatic duct Complications Pseudocysts Obstructed CBD Venous thrombosis – splenic, portal, mesenteric Carcinoma Malabsorbtion

47. NEOPLASM Types Exocrine pancreatic tumor – adenocarcinoma, cystic neoplasm Endocrine pancreatic tumor – insulinoma, gastrinoma Other tumors – lymphoma, metastases ADENOCARCINOMA Clinical – jaundice, weight loss, Courvoisier sign (enlarged, nontender gallblader) Radiographic features Mass effect Alterations of density Extrapancreatic extension Vascular involvement Metastases