Abdominal and Pelvic Radiology Practice Questions

Q: What is the characteristic feature of hepatocellular carcinoma on triphasic CT?

Arterial enhancement with washout. ***Arterial enhancement with washout*** - **Hepatocellular carcinoma (HCC)** classically demonstrates **hyperenhancement** in the arterial phase due to its unique blood supply primarily from the **hepatic artery**. - This is followed by a characteristic **rapid "washout"** of contrast in the portal venous or delayed phases, as the tumor lacks normal portal venous supply and functional bile ducts. *No enhancement* - Lack of enhancement would suggest a **necrotic lesion** or a **benign cyst** rather than a primary malignant tumor like HCC. - This feature is not typical for a viable HCC on a triphasic CT scan. *Delayed enhancement* - **Delayed enhancement** is more typical of **fibrotic lesions** or some benign hepatic masses like **hemangiomas**, which continue to fill in with contrast over time. - It does not show the typical rapid arterial hyperenhancement and washout pattern of HCC. *Progressive enhancement* - **Progressive enhancement** is characteristic of entities like **hepatic hemangiomas**, which show gradual, often nodular, enhancement that follows the blood pool on delayed phases. - This pattern is distinct from the rapid arterial enhancement and subsequent washout seen in HCC.

Q: The most appropriate screening modality for hepatocellular carcinoma

Ultrasound. ***Ultrasound*** - **Ultrasound** is the recommended first-line screening modality for hepatocellular carcinoma (HCC) due to its high sensitivity, non-invasiveness, and cost-effectiveness. - It allows for the detection of **hepatic nodules** in patients with risk factors, such as cirrhosis, facilitating early intervention. *CT abdomen* - While **CT scans** are excellent for characterizing liver lesions and staging HCC, they are generally not used for routine screening due to radiation exposure and higher cost. - CT is typically employed as a **diagnostic follow-up** after an abnormal ultrasound finding. *MRI abdomen* - **MRI** provides superior soft tissue contrast and is often used for definitive diagnosis and characterization of liver lesions, especially when ultrasound or CT findings are equivocal. - However, its high cost and longer acquisition time make it unsuitable for **routine screening purposes**. *PET scan* - **PET scans** are primarily used in oncology for evaluating metastatic disease and assessing treatment response, rather than for primary screening of HCC. - HCC is often not highly **fluorodeoxyglucose (FDG)-avid**, limiting the utility of routine PET scanning for initial detection.

Q: Not a feature of rectosigmoid endometriosis on MRI

T2 hyperintensity. ***T2 hyperintensity*** - Endometriotic implants typically demonstrate **T1 hyperintensity** due to the presence of **hemorrhage** within the ectopic endometrial tissue. - On T2-weighted images, endometriosis usually appears **hypointense** or **isointense** due to the phenomenon of **T2 shading**, caused by chronic hemorrhage and fibrosis. *Mushroom cap sign* - This sign is characteristic of **deep infiltrating endometriosis** affecting the rectosigmoid. - It describes the appearance where the fibrotic endometriotic nodule infiltrates the bowel wall, creating a mushroom-like shape due to the **thickened muscularis propria** and overlying mucosal folds. *Fat stranding* - **Fat stranding** in the perirectal or perisigmoid fat is a common feature of **inflammatory conditions** including endometriosis. - It indicates **reactive inflammation** around the endometriotic implants, often seen in cases of deep infiltrating endometriosis. *Bowel wall thickening* - **Bowel wall thickening** is a frequent finding in rectosigmoid endometriosis due to **fibrotic reaction**, **smooth muscle hypertrophy**, and **edema** caused by the infiltrating endometrial tissue. - This thickening can lead to narrowing of the bowel lumen and obstructive symptoms.

Q: Most sensitive imaging for detecting active inflammation in Crohn's disease

MR enterography. ***Correct: MR enterography*** - This technique offers superior **soft tissue contrast** and can accurately depict **bowel wall thickening**, **mucosal enhancement**, and **edema**, which are hallmarks of active inflammation in Crohn's disease. - It avoids **ionizing radiation**, making it suitable for monitoring chronic conditions like Crohn's disease, especially in younger patients. - MR enterography is currently considered the **gold standard** for assessing disease activity and extent in Crohn's disease. *Incorrect: CT enterography* - While very good for assessing **bowel wall thickening** and **extramural complications**, its sensitivity for detecting subtle **mucosal inflammation** is slightly lower than MR enterography. - It involves significant **ionizing radiation**, limiting its use for frequent follow-up in young patients. *Incorrect: Small bowel follow-through* - Primarily assesses the **lumen** for strictures, fistulas, and ulcers, but is less sensitive for detecting subtle or early **mucosal inflammation** or **extramural disease**. - It involves **ionizing radiation** and often requires barium contrast, which can be less informative than intravenous contrast used in CT or MR. *Incorrect: Plain radiograph* - Offers very limited information on the **bowel wall** and **mucosal changes** associated with active inflammation. - Primarily used to detect complications like **obstruction** or **perforation** (e.g., free air), not for diagnosing or staging active inflammation.

Q: What does the 'rim sign' on contrast-enhanced CT of the kidney indicate?

Acute pyelonephritis. ***Acute pyelonephritis*** - The "rim sign" on contrast-enhanced CT refers to a **peripheral rim of enhanced renal cortex** surrounding a geographic or wedge-shaped area of hypoenhancement, characteristically seen in acute pyelonephritis. - This finding occurs due to **vasoconstriction and inflammatory edema** in the affected renal parenchyma, causing decreased perfusion and reduced contrast enhancement in the inflamed areas, while the peripheral cortex maintains normal enhancement. - The rim sign indicates bacterial infection spreading through the renal parenchyma with focal areas of decreased perfusion. *Renal infarction* - Renal infarction typically shows a **wedge-shaped defect** with absent enhancement extending to the renal capsule on contrast-enhanced CT due to complete arterial occlusion. - Unlike the rim sign, infarction demonstrates **complete absence of enhancement** in the affected area with sharp demarcation, representing ischemic necrosis rather than inflammatory hypoenhancement. *Xanthogranulomatous pyelonephritis* - This is a **chronic granulomatous infection** associated with obstruction and staghorn calculi, characterized by a **diffusely enlarged kidney** with multiple low-attenuation areas and mass-like appearance. - It does not present with the rim sign but rather shows **replacement of renal parenchyma** by lipid-laden macrophages creating a "bear paw" appearance. *Renal abscess* - A renal abscess appears as a **well-defined, round or oval fluid collection** with thick, enhancing walls on contrast-enhanced CT. - Unlike the rim sign which represents inflammatory hypoenhancement, an abscess is a **localized collection of purulent material** with more organized borders and typically higher degree of wall enhancement.

Q: Which is the most sensitive imaging modality for detecting liver metastases?

MRI with contrast. ***MRI with contrast*** - **Magnetic resonance imaging (MRI)** with **gadolinium-based contrast agents** (particularly hepatocyte-specific agents like gadoxetic acid) combined with **diffusion-weighted imaging (DWI)** is considered the most sensitive imaging modality for detecting liver metastases due to its superior soft tissue contrast resolution. - It allows for better characterization of lesions, particularly small ones (<1 cm), and distinguishes them from benign liver lesions. - MRI can detect lesions that are often missed by CT, making it the gold standard for liver metastasis detection. *Ultrasound* - **Ultrasound** is often the initial imaging modality for liver evaluation due to its availability and low cost, but its sensitivity for detecting small metastases is limited and highly operator-dependent. - It may miss small or **isoechoic lesions**, especially in patients with fatty liver disease. *PET scan* - **PET (Positron Emission Tomography)** scans are useful for detecting metabolically active lesions and distant metastases throughout the body, but their spatial resolution for small liver lesions can be lower than MRI. - While good for whole-body staging, it may not be as sensitive as MRI for detecting tiny metastases within the liver parenchyma itself. *CT with contrast* - **Computed tomography (CT)** with intravenous contrast is a widely used and effective modality for detecting liver metastases, but it is generally less sensitive than MRI, especially for lesions under 1 cm. - CT scans can sometimes struggle to differentiate small metastases from benign lesions or areas of perfusion abnormality.

Q: Which of the following is not true about adrenal adenoma on CT?

Calcification is common. ***Calcification is common*** - **Adrenal adenomas** are typically **lipid-rich** and generally do not calcify. - The presence of **calcification** in an adrenal mass is more suggestive of other etiologies like **pheochromocytoma**, **adrenal carcinoma**, infection, or hemorrhagic cysts, rather than a benign adenoma. *Low attenuation* - **Adrenal adenomas** commonly demonstrate **low attenuation** (typically <10 Hounsfield Units on unenhanced CT) due to their high intracellular **lipid content**. - This low attenuation is a key characteristic used to differentiate benign adenomas from other adrenal lesions. *Rapid contrast washout* - **Adrenal adenomas** exhibit **rapid contrast washout** on delayed CT imaging, which is a diagnostic hallmark. - This characteristic washout pattern helps distinguish them from malignant lesions or **pheochromocytomas** that retain contrast for longer periods. *Well-defined borders* - **Adrenal adenomas** usually present as **well-defined**, round or oval masses, reflecting their benign and encapsulated nature. - This distinct border helps differentiate them from infiltrative or aggressive lesions like adrenal carcinomas, which often have irregular or ill-defined margins.

Q: How does 'hepatic vein thrombosis' present on Doppler ultrasound?

Absent or reversed flow. ***Absent or reversed flow*** - **Hepatic vein thrombosis** directly obstructs blood flow, leading to either an absence of detectable flow or, in some cases, reversal of flow due to high downstream pressure and collateral formation. - This finding on **Doppler ultrasound** is a key indicator of **Budd-Chiari syndrome**, caused by the obstruction of hepatic venous outflow. *Anechoic appearance* - An **anechoic appearance** on ultrasound typically refers to a fluid-filled structure, such as a cyst or gallbladder, which allows sound waves to pass through without reflection. - While thrombosis can affect the lumen of a vessel, the thrombus itself often has some echogenicity, and the primary Doppler finding relates to flow dynamics, not simply the anechoic nature of the vessel. *Increased flow* - **Increased flow** in the hepatic veins would suggest a hyperdynamic state or shunting, which is not characteristic of venous thrombosis. - Thrombosis causes obstruction, leading to a reduction or cessation of flow, not an increase. *Normal triphasic flow* - **Normal triphasic flow** in the hepatic veins is characterized by three distinct phases corresponding to cardiac cycles: antegrade flow during systole and diastole, and a brief period of reversed flow during atrial contraction. - The presence of thrombosis would disrupt this normal pattern, making it an unlikely finding in **hepatic vein thrombosis**.

Q: What is the next best step for a 22-year-old with a hepatic hemangioma on ultrasound?

MRI. ***MRI*** - **Magnetic Resonance Imaging (MRI)** is the most sensitive and specific imaging modality for confirming the diagnosis of a **hepatic hemangioma** due to its characteristic enhancement patterns. - An MRI with contrast (e.g., gadolinium) can definitively distinguish a hemangioma from other **benign or malignant liver lesions**, especially when the ultrasound findings are equivocal. *Angiography* - **Angiography** is an invasive procedure and is typically reserved for cases where **embolization** or surgical resection of a very large or symptomatic hemangioma is being considered. - It is not the initial diagnostic choice for confirming a suspected hemangioma identified on **ultrasound**. *CT* - A **CT scan** with contrast can also characterize a hemangioma, showing peripheral nodular enhancement followed by progressive centripetal fill-in. - However, **MRI** generally offers superior soft tissue contrast and provides more definitive diagnostic features for hemangiomas, particularly in younger patients where radiation exposure from CT is a concern. *Biopsy* - **Biopsy** of a suspected hepatic hemangioma is generally contraindicated due to the risk of **hemorrhage** and is rarely necessary for diagnosis. - Imaging characteristics (especially on MRI) are usually sufficient to confirm the diagnosis without the need for an invasive procedure.

Q: The 'onion skin' appearance of a liver lesion on ultrasound is suggestive of which diagnosis?

Hydatid cyst. ***Hydatid cyst*** - The classic "**onion skin**" or "water lily" sign on ultrasound is characteristic of a **hydatid cyst**, representing detached endocyst membranes floating within the cyst. - This appearance is due to the degeneration and separation of the inner germinal layer from the outer fibrous layer, often seen in **Echinococcus granulosus** infection. *Hepatocellular carcinoma* - **Hepatocellular carcinoma** (HCC) typically appears as a heterogeneous mass on ultrasound, often with a **mosaic pattern** and sometimes a **capsule**, rather than an "onion skin" appearance. - Features like **portal vein thrombosis** and **washout** on contrast-enhanced imaging are more characteristic of HCC. *Focal nodular hyperplasia* - **Focal nodular hyperplasia** (FNH) is a benign lesion characterized by a central scar and spokewheel vascular pattern on imaging, not an "onion skin" appearance. - It usually appears as a **well-circumscribed mass** that is iso- or slightly hyperechoic on ultrasound. *Hepatic abscess* - A **hepatic abscess** typically presents as a hypoechoic, ill-defined mass with internal debris and sometimes gas on ultrasound. - It often has an **irregular wall** and can show **posterior acoustic enhancement**, but not the "onion skin" layering.

Question 1

What is the characteristic feature of hepatocellular carcinoma on triphasic CT?

Accepted Answer

Arterial enhancement with washout

Answer

No enhancement

Answer

Delayed enhancement

Answer

Progressive enhancement

Question 2

The most appropriate screening modality for hepatocellular carcinoma

Accepted Answer

Ultrasound

Answer

CT abdomen

Answer

MRI abdomen

Answer

PET scan

Question 3

Not a feature of rectosigmoid endometriosis on MRI

Accepted Answer

T2 hyperintensity

Answer

Mushroom cap sign

Answer

Fat stranding

Answer

Bowel wall thickening

Question 4

Most sensitive imaging for detecting active inflammation in Crohn's disease

Accepted Answer

MR enterography

Answer

Small bowel follow-through

Answer

CT enterography

Answer

Plain radiograph

Question 5

What does the 'rim sign' on contrast-enhanced CT of the kidney indicate?

Accepted Answer

Acute pyelonephritis

Answer

Renal infarction

Answer

Xanthogranulomatous pyelonephritis

Answer

Renal abscess

Question 6

Which is the most sensitive imaging modality for detecting liver metastases?

Accepted Answer

MRI with contrast

Answer

Ultrasound

Answer

PET scan

Answer

CT with contrast

Question 7

Which of the following is not true about adrenal adenoma on CT?

Accepted Answer

Calcification is common

Answer

Low attenuation

Answer

Rapid contrast washout

Answer

Well-defined borders

Question 8

How does 'hepatic vein thrombosis' present on Doppler ultrasound?

Accepted Answer

Absent or reversed flow

Answer

Anechoic appearance

Answer

Increased flow

Answer

Normal triphasic flow

Question 9

What is the next best step for a 22-year-old with a hepatic hemangioma on ultrasound?

Accepted Answer

MRI

Answer

Angiography

Answer

CT

Answer

Biopsy

Question 10

The 'onion skin' appearance of a liver lesion on ultrasound is suggestive of which diagnosis?

Accepted Answer

Hydatid cyst

Answer

Hepatocellular carcinoma

Answer

Focal nodular hyperplasia

Answer

Hepatic abscess

Abdominal and Pelvic Radiology — MCQs

Abdominal and Pelvic Radiology — MCQs

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