Liver RadRev

Question 1

Hepatocellular carcinoma (HCC) develops along a spectrum. Describe the spectrum of HCC development including some imaging manifestations.

Answer 1

HCC starts with regenerative nodules that progress to dysplastic nodules and then to HCC. Key imaging manifestations include that dysplastic nodules tend to be dark on T2 weighted images and HCC tends to be bright on T2 weighted images. Regenerative nodules may be bright or dark on T2 weighted images but typically do not enhance or washout differently than normal liver. Dysplastic nodules may have arterial enhancement but no washout. HCC demonstrates early arterial enhancement and delayed washout. Key imaging manifestations for HCC is a T2 bright mass vs masses with arterial enhancement and delayed washout, with co-existing findings of cirrhosis and portal hypertension.

Question 2

What are some of the common risk factors for development of hepatocellular carcinoma?

Answer 2

Cirrhosis of any cause, acute hepatitis B with or without cirrhosis and chronic hepatitis B with cirrhosis, hepatitis C, hemochromatosis (HCC accounts for about 1/3 of deaths in hemochromatosis patients), glycogen storage disease, alpha-1 antitrypsin deficiency, other entities to include Budd Chiari syndrome.

Question 3

HCC accounts for _____ of deaths in hemachromatosis patients

Answer 3

1/3

Question 4

True or false: most patients with HCC will have an elevated alpha fetal protein (AFP) level?

Answer 4

True, up to 95% of HCC patients will have elevated AFP levels.

Question 5

What are imaging manifestations for the fibrolamellar HCC variant to look for on board exams?

Answer 5

Buzzword on board exams for fibrolamellar HCC is a central nonenhancing T2 dark scar on MRI. The central scar may be calcified on CT. Additionally, fibrolamellar HCC tends to develop in patients younger than 35 years without cirrhosis and with normal AFP levels. Fibrolamellar HCCs are aggressive so you may also be shown local nodal and distant metastatic disease.

Question 6

If you see a hepatic mass with a central scar demonstrating delayed enhancement on MRI what is this typical for?

Answer 6

Focal nodular hyperplasia classically has a central scar (T2 bright) that demonstrates delayed enhancement. T2 bright scar = you have a bright future

Question 7

What are other imaging manifestations of focal nodular hyperplasia (FNH) on MRI?

Answer 7

FNH presents with a spoke wheel or cut grapefruit appearance on post-contrast imaging that is commonly isointense to liver (hence a “stealth lesion”) on pre-contrast T1 and T2 weighted images. With gadolinium on arterial enhanced images you often see a cut grapefruit appearance due to enhancement in the mass surrounding a non-enhancing central scar with radiating bands. On delayed post-contrast images, the central scar will classically show delayed enhancement. Most common clinical history would be a mass in a middle-aged woman. FNH’s may regress with age. Note that FNH’s do not demonstrate washout of contrast as in HCC.

Question 8

What nuclear medicine scan should you remember for FNH diagnosis on board exams?

Answer 8

On board exams I would remember that FNH can show uptake on a sulfur colloid liver scan. An FNH has normal hepatocytes around abnormally arranged ducts and Kupffer cells. As the lesion contains reticuloendothelial system cells you would expect that the RES will show sulfur colloid uptake. Other hepatic masses such as a hepatic adenoma, HCC, or metastasis would not be expected to show sulfur colloid uptake because these do not contain functioning Kupffer cells.

Question 9

If a board exam question shows you a liver lesion and gives you a clinical history of a woman on oral contraceptives, what lesion should you think of first?

Answer 9

A question showing a liver lesion and providing a clinical history of oral contraceptive use should make you consider a hepatic adenoma as the most likely diagnosis. An alternative history also supporting a hepatic adenoma would be a male on anabolic steroids with a liver mass. Key is that hepatic adenomas are classically hormonally induced, thus may also be seen in obese individuals.

Question 10

What is the imaging appearance of a hepatic adenoma?

Answer 10

Most commonly hepatic adenomas will present as a potentially large solitary mass in the right hepatic lobe (most common). . Hepatic adenomas classically contain internal fat (although male hepatic adenomas may not have fat) and/or hemorrhage. On MRI, hepatic adenomas would classically show internal fat manifested by signal dropout on out of phase compared to in phase images, with early arterial enhancement and return to normal liver enhancement levels on delayed postcontrast images

Question 11

multiple hepatic adenomas

Answer 11

If you see multiple hepatic adenomas you can consider entities like glycogen storage disease (von Gierke’s disease).

Question 12

What are similarities and differences of HCC and hepatic adenomas on imaging?

Answer 12

Similarities include hepatic lesions that may contain fat and both can be well circumscribed. Differences include a typical homogenous post-contrast appearance of an adenoma and heterogeneous appearance of HCC. Both lesions demonstrate arterial enhancement but only HCCs classically show washout. If you have chronic liver disease it is HCC and not an adenoma on board exams.

Question 13

What is the classic nuclear medicine appearance of hepatic adenoma versus focal nodular hyperplasia on a technetium sulfur colloid scan?

Answer 13

FNH will show uptake on Tc sulfur colloid as it has functioning Kupffer cells. Hepatic adenomas have poorly functioning or dysfunctional Kupffer cells so these would classically not show uptake and may even appear photopenic compared to liver on a Tc SC scan.

Question 14

What is the imaging appearance of hepatic hemangiomas on CT or MRI?

Answer 14

On MRI hemangiomas are T2 bright masses. On CT hemangiomas are hypodense lesions. On both CT and MRI hemangiomas show peripheral nodular enhancement with progressive fill in of central enhancement on delayed enhancement images. Of note, because blood flow is slow and blood pools within these lesions, hepatic hemangiomas may enhance for about 30 minutes following contrast administration. Classic for hepatic hemangiomas is peripheral nodular interrupted enhancement with progressive filling in of contrast on more delayed post-contrast sequences. Really large hemangiomas can have venous pooling in venous lakes and central blood clots and can look really heterogeneous, especially on T2 weighted images.

Question 15

What is the ultrasound appearance of a hepatic hemangioma?

Answer 15

On ultrasound hemangiomas are well defined uniformly hyperechoic lesions. Surprisingly there is typically no visible doppler blood follow identified as the blood flow is often too slow to be identified.

Question 16

Uptake with what nuclear medicine study is most typical for hepatic hemangiomas on board exams?

Answer 16

If you see a liver mass showing uptake on a tagged red blood cell nuclear medicine study think hepatic hemangioma. I remember this as hemangioma has “hemangio” in the name which makes me think of blood as in a tagged RBC study. If you remember that hepatic hemangiomas have slow blood flow and blood pools in the lesion it makes perfect sense that tagged RBCs would also pool in the lesion and would therefore show uptake on nuclear medicine scintigraphy. The “hemangio” in the name is your clue that this would show up on a tagged RBC scan because the name is telling you about vascularity.

Question 17

What is the “starry sky” appearance of the liver on ultrasound and what disease state does this suggest?

Answer 17

The starry sky appearance is a sign of hepatitis on ultrasound and shows echogenic fat around portal triads that stands out due to background liver edema.

Question 18

Are benign liver masses more common or less common in a cirrhotic liver?

Answer 18

Benign liver masses tend to go away or not develop and are much less common in a cirrhotic liver. Therefore, treat any liver lesion in a cirrhotic patient with some suspicion.

Question 19

Carcinoid and HCC are both arterial enhancing masses—how do you tell the difference between these on board exams?

Answer 19

If you see chronic liver disease it is HCC on board exams. In general, chronic liver disease is highly inhospitable to both benign masses and metastatic disease so it is less likely to get liver metastases in the setting of chronic liver disease. So, if you see a Hypervascular mass in chronic liver disease it is HCC versus a Hypervascular metastasis such as carcinoid. Other tips include seeing the carcinoid tumor to suggest that the liver lesion is a metastasis.

Question 20

How do you tell a carcinoid metastasis from a hemangioma on CT or MRI?

Answer 20

Carcinoid will have a continuous rind of enhancement. Hemangioma will show interrupted/discontinuous peripheral enhancement. Also, on board exams with they would almost certainly show you the primary carcinoid tumor in the abdomen/pelvis along with the hepatic metastases.

Question 21

How to you tell a hemangioma from a hepatic metastasis on board exams?

Answer 21

Look for the T2 bright signal to confirm a hemangioma (CSF bright). Metastases would not be expected to be as bright on T2 weighted images. Both can show interrupted peripheral nodular enhancement. Metastases also may demonstrate a thick rind of enhancement unlike hemangiomas.

Question 22

What are common imaging manifestations of cholangiocarcinoma?

Answer 22

Cholangiocarcinoma presents as infiltrative hepatic lesion(s) with delayed enhancing soft tissue that grows around and constricts the biliary tree with co-existing peripheral biliary dilatation and contraction of the hepatic capsule. You may also see portal/hepatic vein encasement without visible tumor thrombus unlike HCC which has luminal thrombus and vascular invasion. HCC grows into the portal vein whereas cholangiocarcinoma narrows the portal vein from the outside. If cholangiocarcinoma causes biliary obstruction you can get bilomas that may have secondary inflammation due to hepatic irritation.

Question 23

What are some of the common risk factors for development of cholangiocarcinoma?

Answer 23

Elderly males, history of primary sclerosing cholangitis (top risk factor in US), recurrent pyogenic cholangitis, clonorchis sinensis parasitic disease (aka liver fluke), hepatitis B/C, HIV, alcohol abuse, thorotrast exposure.

Question 24

What is a Klatskin tumor?

Answer 24

A Klatskin tumor is a cholangiocarcinoma located at the bifurcation of the right and left hepatic ducts, sometimes termed a hilar cholangiocarcinoma. These are aggressive and often obstruct the biliary duct so stricture/narrowing at the bifurcation on MRCP would raise concern for a possible Klatskin tumor.

Question 25

Are primary sclerosing cholangitis patients at higher risk for developing cholangiocarcinoma or hepatocellular carcinoma?

Answer 25

With PSC risk of cholangiocarcinoma exceeds that of HCC.

Question 26

What hepatic tumor is most associated with thorotrast exposure?

Answer 26

Hepatic angiosarcoma which is a very rare tumor but the most common primary sarcoma of the liver. Neurofibromatosis and hemochromatosis patients are also at risk for hepatic angiosarcoma.

Question 27

What MRI contrast agent is predominantly biliary secreted?

Answer 27

Eovist—therefore some centers use this preferentially for liver evaluation, transplant and biliary leak evaluation.

Question 28

What are the 2 most common primary hepatic malignancies?

Answer 28

HCC is #1. Cholangiocarcinoma is #2.

Question 29

Besides hepatic cysts, what are the 2 most common hepatic masses overall?

Answer 29

Metastases are #1. Hemangiomas are #2.

Question 30

What are the most common primary cancers that metastasize to the liver?

Answer 30

First, I would think of colon cancer. If you see multiple calcified hepatic metastases think mucinous tumors of the colon, ovary or pancreas.

If you see hypervascular metastases consider melanoma, renal cell carcinoma, carcinoid tumor, islet cell tumor, thyroid and choriocarcinoma.

Question 31

How does Kaposi sarcoma manifest in the liver and what clinical history do you expect with Kaposi sarcoma?

Answer 31

Always look for an AIDS history with low CD4 count in the question stem whenever considering Kaposi sarcoma. In the liver, Kaposi Sarcoma presents with infiltration of the periportal tissues and may look like biliary dilatation on non-contrast imaging. On post-contrast imaging biliary/periportal nodular enhancement is seen. *If you are presented with what looks like biliary ductal dilatation on a noncontrast CT in a patient with AIDS you always must consider Kaposi Sarcoma for board exam purposes and get a post-contrast scan to see the abnormal enhancement. An alternative history that can raise concern for Kaposi sarcoma is history of organ transplantation with immunosuppression

Question 32

How does Kaposi sarcoma present elsewhere in the body?

Answer 32

Kaposi sarcoma can commonly present with purple cutaneous plaques on the legs, and in addition to the liver findings of biliary infiltration with periportal enhancing nodules you can also see pulmonary nodules with mediastinal/hilar nodal enlargement. Remember that lymphoma is on the differential of Kaposi sarcoma and classically gallium 67 would classically show uptake in lymphoma but not in Kaposi sarcoma, whereas thallium 201 would show uptake in both (due to functioning Na/K ATPases in both— thallium is a potassium analogue)

Question 33

How do you tell a perfusion anomaly from a liver mass or regenerative nodule?

Answer 33

Perfusion anomalies have arterial enhancement without washout and are often wedge shaped and nonmass like in appearance.

Question 34

HIV pt with no fevers, super low CD4 count

Answer 34

Kaposi sarcoma of the liver

In the liver, Kaposi Sarcoma presents with infiltration of the periportal tissues and may look like biliary dilatation on non-contrast imaging. On post-contrast imaging biliary/periportal nodular enhancement is seen. *If you are presented with what looks like biliary ductal dilatation on a noncontrast CT in a patient with AIDS you always must consider Kaposi Sarcoma for board exam purposes and get a post-contrast scan to see the abnormal enhancement.

Radiographics Kaposi article: https://pubs.rsna.org/doi/pdf/10.1148/rg.264055129

Question 35

Answer 35

On ultrasound hemangiomas are well defined uniformly hyperechoic lesions. Surprisingly there is typically no visible doppler blood follow identified as the blood flow is often too slow to be identified.