Liver (for PBR 2) Flashcards
Term used for transient enhancement differences seen during either arterial phase imaging or portal venous imaging on MDCT or dynamic MRI
Transient hepatic attenuation differences (THAD) or
Transient hepatic intensity differences (THID) or
Transient hepatic enhancement differences (THED)
Findings in hepatic perfusion abnormalities
- Hyperenhancement in the arterial phase
- Isoenhancement in portal venous and delayed phase
- Isoattenuation on unenhanced CT
- Isointensity on MR unenhanced T1, T2, and DWI
Evidence of hepatomegaly
Round of the inferior border of the liver
Extension of the right lobe of the liver inferior to the lower pole of the right kidney
Liver length of how many centimeters is considered enlarged?
Greater than 15.5 cm
Measures in the midclavicular line
It is an elongated inferior tip of the right lobe of the liver
Reidel lobe
Normal variant - when present the left lobe of the liver is correspondingly smaller in size
Most common abnormality by hepatic imaging
Hepatic steatosis
Two most common cause of hepatic steatosis
Alcoholic liver disease
Nonalcoholic fatty liver related to metabolic syndrome
Reliable ultrasound finding of nonalcoholic steatohepatitis (NASH)
- Liver echogenicity is greater than the renal cortex
- Loss of visualization of normal echogenic portal triads
- Poor sound penetration with loss of definition of diaphragm
All three findings must be present to make an unquivocal US diagnosis
Unenhanced CT finding of NASH
- Liver attenuation is 10 HU less than spleen attenuation
OR
Liver attenuation is less than 40 HU - Blood vessels appear brighter than the dark liver on unenhanced CT
Sign seen with fatty liver being dark on unenhanced CT and bright on US
“Flip-flop” sign
Characteristic feature of fatty deposition on all modalities
- Lack of mass effect (no bulging of the liver contour or displacement of intrahepatic vessels)
- Angulated geometric boundaries between involved and uninvolved parenchyma
Most common pattern of fatty liver
a. Diffuse fatty liver
b. Focal fatty liver
c. Focal sparing
d. Multifocal fatty liver
e. Perivascular fatty liver
f. Subcapsular fatty liver
A. Diffuse fatty liver
MC locations of focal fat
Adjacent to the:
Falciform ligament
Gallbladder fossa
Porta hepatis
MC location of fat-spared area in fatty liver
Segment 4
Pattern of fatty liver which is only seen in patients with renal failure on peritoneal dialysis and only when insulin is added to the dialysate
Subcapsular fatty liver
High concentrations of insulin in the subcapsular lier lead to fat deposition
Liver disease that is characterized pathologically by:
- Diffuse parenchymal destruction
- Fibrosis with alteration of hepatic architecture
- Innumerable regenerative nodules (RN) that replace normal liver parenchyma
Cirrhosis
Imaging findings of cirrhosis (7)
- Hepatomegaly (early)
- Atrophy or hypertrophy of hepatic segments
- Coarsening of hepatic parenchymal texture
- Nodularity of the parenchyma, often most noticeable on the liver surface
- Hypertrophy of the caudate lobe and left lobe with shrinkage of the right lobe
- Regenerating nodules
- Enlargement of the hilar periportal space (>10mm)
Creator's notes: Early enlargement Atrophy Coarsening Nodularity Caudate lobe hypertrophy Enlargement of the hilar periportal space (1 cm)
Imaging finding of cirrhosis that reflects parenchymal atrophy
Enlargement of the hilar periportal space
Extrahepatic signs of cirrhosis
- Portosystemic collaterals (as evidence of portal hypertension)
- Splenomegaly
- Ascites
Different causes of nodules in a cirrhotic liver
- Regenerative nodules
- Dysplastic nodules
- Hepatocellular carcinoma
- Confluent fibrosis
- Focal fat infiltration
- Focal fat sparing
- Metastases (rare in cirrhosis)
Most common nodules of cirrhosis
Regenerative nodules
Regular pathologic feature of cirrhosis due to attempted repair of hepatocyte injury
Difference of low-grade dysplastic nodules and high-grade dysplastic nodules
Low-grade DN
- Minimal atypia, no mitosis, not premalignant
- Supplied by portain vein
- No arterial phase enhancement
- Progresses to high-grade
High-grade DN
- Moderate atypia, occasional mitosis, secrete AFP
- Not frankly malignant
- Blood supply by hepatic artery
- Show arterial phase enhancement
Siderotic nodules may be regenerative or dysplastic but are seldom benign.
What imaging finding would consider a benign siderotic nodule on MRI?
< 20 mm
Homogeneous on all sequences (low signal)
Isoenhance compared to background cirrhotic nodules in all phases
Major criteria for diagnosis of hepatocellular carcinoma (LIRADS)
- Hyperenhancement in arterial phase definitely greater than background liver
- “Washout”
- Threshold growth
Definition of “washout” of HCC
During contrast-enhanced study:
Visual hypointensity/ hypodensity of the lesion compared with background liver on portal venous and delayed phases
Definition of Threshold Growth in HCC
Diameter increase of the mass by 5 mm or more
50% increase in diameter compared to prior examination ≤6 months
100% increase in diameter compared to prior examination at >6 months
New 10-mm lesion regardless of time interval
Ancillary sings of HCC by LI-RADS criteria
*Low yield
- Mild to moderate hyperintensity on T2WI
- Restricted diffusion on MR
- Rim of perilesional enhancement (corona enhancement)
- Mosaic architecture
- “nodule within a nodule” (HCC developing within a DN)
- Intralesional fat
- Intralesional iron sparing
- Intralesional fat sparing
- Diameter increase less than that defined as threshold growth
LI-RADS criteria favoring benign nodule
*Low yield
5 and 6 - indicates no growth
- Homogeneous marked hyperintensity on T2
- Homogeneous marked hypointensity on T2 or T2*
- Intralesional vessels without distortion
- Nodule enhancement parallels blood pool
- Decrease diameter
- Stable diameter for > 2 years
*Creator's note simplify: #1 is a cyst #2 is probably a siderotic nodule #3 is a focal fat # 4 is probably a hemangioma
This refers to a bulging hypertrophied expanse of the liver surrounded by atrophic fibrotic liver parenchyma
Hypertrophic pseudomass
Imaging features that favor pseudomass over tumor include preservation of hepatic architectures and presence of undistorted vessels traversing the lesion
This refers to mass-like areas of fibrosis found in livers with advance cirrhosis
Confluent fibrosis
This is a pathologic increase in portal venous pressure that results in the formation of portosystemic collateral vessels that divert blood flow away from the liver and into the systemic circulation
Portal hypertension
Signs of portal hypertension
- Visualization of portosystemic collaterals
- Increased portal vein diameter (>13 mm)
- Increased superior mesenteric and splenic vein diameters (>10 mm)
- Portal vein thrombosis
- Calcifications in the portal and mesenteric veins
- Splenomegaly due to vascular congestion
- Ascites
- Reversal of flow in any portion of the portal venous system (hepatofugal flow)
What are the portosystemic collaterals affected in portal hypertension?
Coronary Gastroesophageal Splenorenal Paraumbilical Hemorrhoidal Retroperitoneal
Causes of portal vein thrombosis
Complication of cirrhosis
Portal vein invasion or compression by tumor
Hypercoagulable states
Inflammation (pancreatitis)
*Creator;s notes:
Cirrhosis, neoplasm, inflammation, blood problem
Characteristic of a malignant thrombus in the portal vein
It is contiguous with and extends from the primary tumor
Portal vein is expanded, filled with tumor in vein of the same imaging characteristics, including enhancement, as the primary tumor
Characteristic of a bland thrombus in the portal vein
It fills a portal vein of near-normal size
On MR bland thrombus is of low signal because of its hemosiderin content
Bland thrombus does not enhance
The thrombus is hyperintense on T1WI when acute and isointense when chronic
This develops when small collateral veins adjacent to the portal vein expand and replace the obliterated portal vein
Cavernous transformation of the portal vein
These collateral veins appear as a tangle of small vessels surrounding the thrombosed portal vein
This refers to a group of disorders characterized by obstruction to hepatic venous outflow involving one or more hepatic veins
Budd-Chiari syndrome
Causes of Budd-Chiari syndrome
Coagulation disorder
Membranous webs obstructing hepatic veins or IVC
Malignant tumor invasion
CE CT scan finding of Budd-Chiari syndrome
Early images - central liver enhancement prominently while the peripheral liver enhances weakly
Delayed images - the periphery of the liver is enhanced, while the contrast has washed out of the central liver
What is the “comma” sign?
It is a comma-shaped intrahepatic collateral vessels that may be seen on CT or MR in Budd-Chiari syndrome
Diffuse liver disease that is a common complication of congestive heart failure and constrictive pericarditis
Passive hepatic congestion