GI imaging Flashcards
How many liver segments are there?
What separates superior and inferior segments?
What forms the segmental borders in the axial plain?
Portal veins divide superior from inferior segments
Hepatic veins form the segmental borders in the axial plane
How to remember which segments are superior/inferior and left/right?
- Mnemonic for remembering the segments:
Superior segments, from left to right: 2, 4, 8, 7, 1 (caudate). 2 doubled is 4; 4 doubled is 8; 8 minus 1 is 7. Inferior segments, from left to right: 3, 4, 5, 6. - Segments 2, 3, and 4 are in the left lobe of the liver.
- Segments 5, 6, 7, 8 are in the right lobe of the liver.
Where does the caudate lobe of the liver drain and how does this affect it in cirrhosis?
Caudate lobe drains directly to the IVC, not into the hepatic veins
The caudate lobe hence is not affected in early cirrhosis since the direct drainage to the IVC spares the caudate from increased venous pressures due to portal hypertension. This leads to compensatory hypertrophy of the caudate lobe.
Direct venous drainage to the IVC allows the caudate lobe to bypass the increased hepatic venous pressures seen in Budd-Chiara syndrome. Compensatory hypertrophy of the caudate lobe may preserve liver function in these patients.
Liver USG, what is seen?
Hepatic steatosis causes increased sound attenuation, leading to poor visualization of deeper structures
What is seen and dx?
Treatment?
Primary haemochromatosis is the most common cause of iron overload, due to a genetic defect causing increased iron absorption through the GIT
Excess iron is deposited in hepatocytes (not the Kupffer cells that make up the intrahepatic reticuloendothelial system or RES), pancreas, myocardium, skin and joints. Excess iron in hepatocytes can cause cirrhosis.
Liver and pancreas are markedly T2 hypointense an show signal dropout on in phase images. The spleen and bone marrow are normal since the RES is not involved.
Treatment of primary hemochromatosis is phlebotomy
Which organs are effected in secondary haemochromatosis?
What are the causes of secondary haemochromatisis?
Secondary haemochromatosis is seen in diseases that cause haemosiderosis, where excess iron accumulates within the RES. This may be due to frequent blood transfusions or defective erythrocytosis. Treatment of haemosiderosis is with iron chelators.
RES has large capacity for iron and iron stored in RES is not harmful until it becomes in excess where just as in primary haemochromatosis, hepatocyte iron uptake may lead to cirrhosis.
Image: Secondary hemochromatosis: Multisequence MRI shows diffuse low T2 signal in the liver and spleen with associated signal loss on in-phase imaging compared to out-of-phase imaging, consistent with iron deposition from hemosiderosis in this patient with transfusion-dependent anemia.
What are the causes of hypoattenuating and hyperattenuating liver?
Hypoattenuating liver: fatty liver (hepatic steatosis), hepatic amyloid
Hyperattenuating liver: iron overload is the most common cause of hyperattenuating liver, medications (amiodarone, gold and methotrexate), wilson disease (copper overload), glycogen disease
What are the causs of liver cirrhosis?
Metabolic (alcohol, steatohepatitis, hemochromatosis, or Wilson disease)
Infectious (chornic hep B/C)
inflammatory (primary biliary cirrhosis or wilson disease)
What are the intrahepatic signs of cirrhosis?
What are early signs of cirrhosis?
Expansion of the periportal spaces
Atrophy of the medial segment of the left hepatic lobe in early cirrhosis causes increased fat anterior to the right main portal vein.
Enlargement of caudate lobe is a specific sign of cirrhosis. Specifically, a caudate to right lobe size ratio of >0.65 highly suggests cirrhosis.
The empty gallbladder fossa sign results when hepatic parenchyma surrounding the gallbladder is replaced with periportal fat.
What are the secondary manifestations of cirrhosis?
- Portal hypertension causes splenomegaly and formation of portosystemic collaterals/varices, including recanalization of the paraumbilical vein
Gamna-Gandy bodies are splenic microhemorrhages secondary to portal hypertension. These appear as tiny echogenic foci on US, tiny hypo or hypoattenuating on CT - Gallbladder wall thickening us due to hypoalbuminemia and resultant edema
- Micronodular cirrhosis <3mm (normally associated with alcoholism)
- Macronodular cirrhosis features nodules (>3mm) separated by wide scars and fibrous septae. Macronodular cirrhosis caused by fulminant viral hepatitis which does uniformly affect the liver.
What is the classical appearance of cirrhosis?
What is seen below?
What investigations can be done to test for cirrhosis?
Segmental atrophy and hypertrophy with nodular contour and parenchyma
Axial T2-weighted MR images show nodular contour of the liver with hypertrophy of the left lobe, atrophy of the right lobe, widened periportal space (yellow arrow), and right posterior hepatic notch sign (red arrow) in keeping with cirrhosis. This patient had a history of hepatitis C.
MR elastography: non invasive technique in which the patient wears a device resting over the right hepatic lobe which transmits mechanical waves
Sonoelastography: degree of fiibrosis on chronic liver disease
What is seen and expected results for dx?
Encapsulated mass that enhances on arterial phase and washes out on portal venous phase with an enhancing capsule.
HCC is often locally invasive and tends to invade into the portal and hepatic veins, IVC and bile ducts.
In contrast, cholangiocarcinoma and metastases to the liver area much less likely to do so.
What is the LI-RADS scoring system for HCC on CT and MRI?
Ranges from LR-1 (favoring benignity) to LR-5 (favoring malignancy)
Major criteria
* Arterial enhancement
* Non peripheral washout on portal venous and delayed phases
* Enhancing capsule/pseudocapsule seen in portal venous or delayed phases
* Threshold growth with diameter increase of >50% in <6 months
Ancillary findings favoring HCC including non enhancing capsule, nodule in nodule architecture, mossaic architecture, fat in mass, blood products in mass.
Treatmnet options: partial hepatectomy, orthotopic liver trnasplantation, radiation therapy, percutaneous ablation, and transcatheter embolization
Fibrolamellar carcinoma is a rare subtype of HCC that occurs in young patients without cirrhosis. Better prognosis than HCC. AFP is not elevated.
A fibrotic central scar is classic, which is hypointense on T1 and T2W MRI. Does not have capsule.
What is the appearance of hepatic metastases, which phase of imaging is best used to visualize?
Appearance on ultrasound?
Metastases supplied by branches of the hepatic artery. Most metastases are hypovascular and best appreciated on portal venous phase.
On MRI, metastatic lesions tend to be hypointense on T1W and hyperintense on T2W.
Ultrasound: hypoechoic rim producing a target sign.
What are hypovascular and hypervascular hepatic metastases?
Hypovascular: breast, pancreas, lung, lymphoma
Hypervascular: melanoma, renal cell carcinoma, carcinoid/choriocarcinoma, thyroid
What are calcified and cystic hepatic metastases?
Calcified: mucinous cancers (colon, gastric, ovarian), osteosarcoma, treated lymphoma
Cystic: ovarian cystadenocarcinoma, GI sarcoma
What is dx?
DDx?
Dx: epithelioid hemangioendothlioma is a rare vascular malignancy that causes multiple spherical subscapular masses. It is a cause of capsular retraction.
ddx:
* Mass forming cholangiocarcinoma
* Fibrolamellar HCC
* Epithelioid hemangioendothlioma
* Pseudocirrhosis (Macronodular liver contour with capsular retraction due to treated metastases)
* Confluent hepatic fibrosis
Hemangioma: Dynamic contrast-enhanced T1-weighted MRI (early arterial top left image to delayed bottom left image) shows a segment 8 lesion (yellow arrows) demonstrating peripheral discontinuous nodular enhancement. There is progressively increasing centripetal enhancement towards the center of the lesion on delayed images. The signal intensity of the peripheral enhancement is similar to that of the aorta.
The hemangioma is hyperintense on the T2-weighted image (bottom right image).
IMPORTANT: hepatic cavernous haemangioma is the most common benign hepatic neoplasm. It is composed or disorganized endothelial cell lined pockets of blood vessels, supplied by a peripheral branch of the hepatic artery
What is seen and dx?
What other nuclear imaging used to confirm?
- Hepatic adenoma is a benign hepatic neoplasm containing hepatocytes, scattered Kupffer cells, and no bile ducts.
The absence of bile ducts makes a nuclear medicine HIDA scan a useful test to distinguish between focal nodular hyperplasia (which contains bile ducts and would be positive on HIDA) verses a hepatic adenoma, which does not contain bile ducts and will show a paucity of uptake on HIDA.
What are the enhancement patterns of common hepatic masses (HCC, FNH, hepatic adenoma, hypervascular metastasis, non-hypervascular metastasis)
Hepatic abscess most commonly caused by a bowel process (through portal system to the liver). Common causes include diverticulitis, appendicitis, crohns disease, and bowel surgery. Ecoli is the most common causative organism.
Others: entamoeba histolytica (parasitic) with 99% presentation of pain (dome of right lobe)
Apart from pyogenic abscess in the liver what other infections are possible?
TB
Fungal infection
Histoplasmosis
Pneumocystis jirovecii
Candidiasis
Liver
Hepatic echinococcus: Ultrasound (left image) shows a complex, primarily hypoechoic mass in the superior aspect of the liver containing a hyperechoic undulating membrane (red arrow). Contrast-enhanced CT (right image) shows a fluid-attenuating cystic mass (yellow arrows) containing an undulating membrane (red arrow).
- On CT and MRI, a hydatid cyst is a well-defined hypoenhancing cystic mass featuring a characteristic floating membrane or an associated daughter cyst. Peripheral calcification may be seen on CT.
- Classic ultrasound appearance is a large liver cyst with numerous peripheral daughter cysts. A highly suggestive finding is the change in position of daughter cysts as the patient is repositioned.
The water-lily sign is an undulating membrane within the hydatid cyst.
Hydatid sand is a fine sediment caused by separation of the membranes from the endocyst.
What are fat containing lesions in the liver?
Focal fat
Adenoma
HCC
Angiomyolipoma, lipoma, pseudolipoma of the Glissons capsule
What are central scar lesions in liver ultrasound?
FNH
Fibrolamellar HCC
Giant haemangioma
What is the AAST liver injury scale grading scale?
What criteria is used for consideration of liver transplantation?
Milan criteria is used to assess appropriateness of liver transpantation in those with HCC/cirrhosis
3 criterias
* Single tumor <5cm or up with 3 tumors, each with diameter <3cm
* No extrahepatic involvement
* No major vascular involvement
What are post operative appearance after liver transplant?
Periportal edema, minimal ascites, right sided pleural effusion, and a small perihepatic haematoma
What are complications of liver transplantation?
- Vascular: hepatic artery thrombosis is the most common vascular complication. Others include hepatic artery stenosis and pseudoaneurysm, IVC or hepatic vein stenosis or thrombosis and portal vein stenosis or thrombosis
- Biliary: ductal stricture is the most common biliary complication. Leaks and obstruction due to choledocholithiasis is also possible
- Other complications: haematoma, abscess, hepatitis, splenic infarct, recurrent malignancy or primary sclerosing cholangitis (depending on the indication for transplant) and PTLD (lymphoma caused by EBV which can arise after solid organ or bone marrow transplant)
Congenital Budd-Chiari: Axial contrast- enhanced CT shows massive enlargement of the caudate lobe (yellow arrows) and the right posterior segment. There is atrophy of the left lobe and right anterior segments of the liver. Collateral venous drainage in the periphery of the liver is seen as geographic peripheral hyperenhancement (red arrows).
Budd-Chiari is hepatic venous outflow obstruction, which can be thrombotic or non-thrombotic. Thrombotic Budd-Chiari may be due to hypercoagulative states including haematological disorders, pregnancy, oral contraceptive use, malignancy, infection and trauma.
Acute Budd chiari presents with the clinical triad of hepatomegaly, ascites and abd pain.
What is the direction of blood flow to the liver?
What is the normal hepatic vein waveform?
What is blood flow to the liver during portal hypertension?
What are secondary findings of portal hypertension?
- Dilated portal vein
- Splenomegaly
- Gamna-Gandy bodies
- Varices
- Portosystemic shunts (gastroesophageal, paraumbilical or splenorenal)
What is the treatment for portal hypertension?
Transjugular intrahepatic portosystemic shunt (TIPS), which connects a branch of the portal vein to a systemic hepatic vein.
Ultrasound for surveillance of TIPs patency with routine follow up in 1 month, every 3 months for 1st year, and then every 6 to 12 months.
What is the evaluation for TIPS stenosis?
What value is high intraTIPS velocity and low main portal vein velocity?
TIPS stenosis: Spectral Doppler of a TIPS shows a velocity of 45 cm/sec, indicative of stenosis due to slow flow.
High intra-TIPS velocity >190 cm/sec or low intra-TIPS velocity of <90 cm/sec suggests stenosis.
Intra-TIPS velocity change of ± >50 cm/sec since the baseline study is also concerning for stenosis.
Low main portal vein velocity (<30 cm/sec) suggests TIPS stenosis.
What are the causes for increased hepatic vein pulsaility?
What would you expect in ultrasound waveform?
Gallbladder dx and appearnce?
What is the ddx of echogenic macterial within the gallbladder?
Gallstone
Gallbladder sludge
Gallbladder polyp (echogenic, non mobile)
Hyperplastuc cholecystoses (echogenic, non mobile, multiple polyps)
Porcelain gallbladder (echogenic wall, shadowing)
Adjacent bowel (echogenic wall, dirty shadowing)
US findings and expected results for dx?
Acute calculus cholecystitis: Oblique sagittal ultrasound through the gallbladder demonstrates a thickened, echogenic gallbladder wall (arrows). The gallbladder contains numerous echogenic gallstones (red arrow).
Positive sonographic Murphs sign (RUQ pain with pressure from the transducer during inspiration)
Gallbladder wall thickening >3mm
Distended gallbladder >4cm in diameter
Pericholecystic fluid or inflammatory changes in the pericholecystic fat
Color doppler showing hyperemic gallbladder wall
What are the serious complications of acute cholecystitis?
Emphysematous cholecystitis
Gangrenous cholecystitis
Gallbladder perforation
Who is mainly affected by acalculous cholecystitis?
Cholecystitis without gallstones, typically seen in very sick patients such as those in the ICU thought to be due to stasis and hypoperfusion. RIsk factors include sepsis, prolonged total parenteral nutrition, and trauma.
Treatment of acalculous cholecystitis in typically percutaneous cholecystostomy by interventional radiology.