Abdomen

Most important imaging techniques

X-ray

  • plain abdominal radiography:
    before urography,
    before voiding cystourethrography,
    as separated examination in acute abdomen suspicion
  • intravenous urography (IVU):
    contraindications: allergy to i.v. c.m., toxic struma of thyroid, multiple myeloma, hepatic failure.
    CM: on empty stomach
    abdomen x-ray before and 
 7, 15, 25 min. after c.m. administration
  • Voiding cystourethrography:
    search for ureteral reflux,
    urine culture should be negative
    c.m. administration through catheter to urinary bladder
    x-ray before and during miction
  • ERCP (Endoscopic Retrograde CholangioPancreatography):
    with use of endoscope
    c.m. through thin cannula through papilla into Vater ampulla
    we see bill tract and pancreatic duct
  • DSA 
(Digitally Subtracted Angiography):
    c.m. through catheter immediately to examined artery
  • gastrointestinal barium contrast study:
    upper gastrointestinal series
    small bowel follow through, barium enema
    on empty stomach
    barium suspension per os or 
per rectum

ultrasound

  • complex examination and contains: Pancreas, Liver and biliary tree, Kidneys, Spleen, Urinary bladder, Prostate, Genitals, Retroperitoneal space

CT (Computer tomography)

  • only cross-section pictures are origin pictures
  • examination with and without i.v. and per os c.m administration
  • Faster than MRI

MRI (Magnetic Resonance Imaging)

  • any section plane 
( transverse, longitudinal, frontal, oblique) as primary pictures is possible
  • before and after c.m. (ferro- and paramagnetic f. ex. Gd)
  • Slower than CT

LIVER

Density

  • < 50 HU- steatosis fatty
  • 55-65 HU- normal
  • more than > 70 HU - hemochromatosis, Wilson disease

Cystic liver lesions

  • Simple hepatic cyst are common benign LESIONS
  • They can be solitary or multiple
  • In uncomplicated cyst – no septa, no contrast enhancement
  • Multiple hepatic cysts occur commonly in patients with autosomal dominant polycystic kidney disease (ADPKD)
  • The cysts do not always have smooth margin and may lead to hepatic enlargement or vascular and biliary obstruction
  • The cysts appear as hypoattenuating lesions (0-10 HU) with well-defined outlines
  • Abscess: Unsharp margins, air enclosures, Enhancing rim + edema

Benign tumors

hemangioma

  • 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

Focal Nodular Hyperplasia

  • 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

Malignant tumors

metastases

  • 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

Hepatocellular 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

hepatoblastoma

  • 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

Cirrchosis

  • 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.

Diffuse liver disease

  • Fatty infiltration (steatosis) seen on abdominal CT/MRI/US
  • It may result from metabolic causes (diabetes mellitus, obesity) or hepatic exposure to toxic agents (alcohol consumption, steroids, chemotherapy)

CT morphology

  • 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)

Biliary tract

Cholelithiasis

  • A common disease that affects middle-aged woman
  • Ultrasound is the imaging modality of choice, and cholelithiasis is usually an incidental finding at CT or MRI

CT

  • 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)

Tumors

Bile duct carcinoma

  • 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

Gallbladder Carcinoma

  • 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

Spleen

Cystic splenic lesions

  • Congenital cyst: 
hypoattenuating (<20HU), smooth margins, homogenous
  • Post-traumatic cyst: 
hypo- to hyperattenuating, smooth margins, homogenous, possible wall calcifications
  • Abscess:
 hypoattenuating, occasionally with indistinct margins; usually does not show rim enhancement

Solid splenic lesions

Metastases

  • 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

lymphoma

  • 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

Splenomegaly

  • Causes: Portal hypertension, Cirrhosis, Portal or splenic vein thrombosis, Leukaemia, Lymphoma
    Metastases, primary neoplasms, Infections (echinococcus, hepatitis, mononucleosis, tuberculosis), Sarcoidosis, Hemodialysis, Collagen diseases

Pancreas

Cystic pancreatic lesions (Pancreatic pseudocysts)

  • collections of necrotic material, blood, and enzymatic fluid that develop due to acute or chronic pancreatitis
  • A pseudocyst that persist longer than six weeks is very unlikely to resolve spontaneously

Solid pancreatic lesions

Pancreatic carcinoma

Pancreatitis

Acute

Chronic

CT morphology

  • 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

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