Abdominal and Pelvic Radiology Practice Questions

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: 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: A 65-year-old woman presents with a palpable abdominal mass and symptoms of bowel obstruction. What is the most appropriate initial imaging study?

CT scan of the abdomen. ***CT scan of the abdomen*** - A **CT scan** is the most appropriate initial imaging study for a patient presenting with an **abdominal mass** and **bowel obstruction symptoms** due to its ability to accurately characterize the mass, identify the level and cause of obstruction, and detect complications. - It provides **detailed cross-sectional images**, allowing for differentiation between intraluminal, intramural, and extraluminal causes of obstruction and assessing for signs of ischemia or perforation. *Abdominal X-ray* - An **abdominal X-ray** can show signs of bowel obstruction (e.g., dilated loops of bowel, air-fluid levels) but provides limited information about the **cause or nature of an abdominal mass**. - It is often used as a **first-line screening tool** but lacks the diagnostic depth needed to fully evaluate an abdominal mass. *MRI of the abdomen* - **MRI** provides excellent soft tissue contrast, but it is generally **not the first-line choice** for acute bowel obstruction due to longer acquisition times and potential artifacts from bowel motion. - It may be considered for further characterization of a mass, particularly for **pelvic masses** or if there are contraindications to CT contrast, but usually after an initial CT. *Barium enema* - A **barium enema** is a contrast study used to visualize the lower gastrointestinal tract and can help identify **colonic obstructions**, polyps, or strictures. - However, it is **contraindicated in cases of suspected bowel perforation** or complete obstruction where the pressurized contrast could worsen the patient's condition.

Q: A 25-year-old female presents with abdominal pain. An MRI shows a lesion with high T2 signal intensity and low T1 signal in the liver. What is the most likely diagnosis?

Hepatic cyst. ***Hepatic cyst*** - A **hepatic cyst** is a benign, fluid-filled lesion that typically demonstrates **high signal intensity on T2-weighted MRI** sequences and **low signal intensity on T1-weighted MRI** sequences due to its simple fluid content. - The absence of internal septations, solid components, or enhancement on post-contrast imaging further supports the diagnosis of a simple cyst. *Hepatic hemangioma* - While often showing **high signal on T2-weighted MRI**, hemangiomas typically exhibit a characteristic **peripheral nodular enhancement** during the arterial phase, with progressive filling in on delayed phases. - They tend to have **intermediate to high signal on T1-weighted MRI**, which is not consistent with the low T1 signal described. *Hepatocellular carcinoma* - **Hepatocellular carcinoma (HCC)** usually presents with **variable signal intensity** on both T1 and T2-weighted MRI, and classically shows **arterial phase hyperenhancement with venous washout**. - Its appearance is much more complex, often with internal heterogeneity, unlike the simple fluid signal described. *Focal nodular hyperplasia* - **Focal nodular hyperplasia (FNH)** typically has **isointense to slightly hyperintense signal** on both T1 and T2-weighted MRI and features a characteristic **central scar** that becomes hyperintense on delayed T2 images. - FNH shows bright, homogeneous enhancement in the arterial phase with rapid washout, and the central scar enhances late.

Q: A patient presents with symptoms of bowel obstruction. An abdominal X-ray shows multiple air-fluid levels. Which of the following additional imaging studies is most appropriate to determine the cause?

CT scan of the abdomen and pelvis. ***CT scan of the abdomen and pelvis*** - A **CT scan** is the gold standard for diagnosing the cause and level of bowel obstruction due to its detailed imaging capabilities. - It can identify the specific **etiology** (e.g., adhesions, tumor, hernia) and differentiate between partial and complete obstruction. *MRI of the abdomen* - While MRI provides excellent soft tissue contrast, it is generally less accessible and more time-consuming than CT for an acute presentation like bowel obstruction. - MRI is often reserved for special cases, such as in pregnant patients to avoid **radiation exposure**, or for evaluating complex pelvic pathologies. *Barium enema* - A **barium enema** is a fluoroscopic study primarily used to visualize the **colon** and **rectum**, and is useful for detecting distal obstructions like colonic strictures or tumors. - It is less effective for evaluating the small bowel or identifying the cause of obstruction in the upper gastrointestinal tract, and can be contraindicated in cases of suspected perforation. *Ultrasound of the abdomen* - **Ultrasound** can detect dilated bowel loops and some causes of obstruction (e.g., intussusception in children, gallstone ileus), but it is often limited by **bowel gas** and operator dependency. - It is generally not as comprehensive as CT for definitively identifying the precise location and cause of an adult small or large bowel obstruction.

Q: What is the imaging finding of barium studies in Crohn's disease?

String sign. ***String sign*** - The **string sign** is a classic finding in Crohn's disease on barium studies, representing severe narrowing of the bowel lumen due to **mural inflammation and fibrosis**. - This appearance is often seen in the **terminal ileum**, which is a common site of Crohn's involvement, and indicates a stenosis that resembles a thin string of barium. *Apple core lesion* - An **apple core lesion**, or napkin-ring sign, is characteristic of an **annular constricting carcinoma of the colon**. - It describes a circumferential narrowing of the bowel lumen with overhanging edges, distinct from the linear narrowing of Crohn's. *Bird beak sign* - The **bird beak sign** is typically associated with **achalasia**, a disorder of esophageal motility. - It describes the smooth, tapered narrowing of the distal esophagus, resembling a bird's beak, due to failure of the lower esophageal sphincter to relax. *Coiled spring appearance* - The **coiled spring appearance** is a classic radiographic sign of **intussusception**, where one segment of the bowel telescopes into another. - This finding is seen on barium or air enema studies and reflects the barium trapped between the layers of intussuscepted bowel.

Question 1

Not a feature of rectosigmoid endometriosis on MRI

Accepted Answer

T2 hyperintensity

Answer

Mushroom cap sign

Answer

Fat stranding

Answer

Bowel wall thickening

Question 2

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 3

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 4

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 5

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 6

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 7

A 65-year-old woman presents with a palpable abdominal mass and symptoms of bowel obstruction. What is the most appropriate initial imaging study?

Accepted Answer

CT scan of the abdomen

Answer

Abdominal X-ray

Answer

MRI of the abdomen

Answer

Barium enema

Question 8

A 25-year-old female presents with abdominal pain. An MRI shows a lesion with high T2 signal intensity and low T1 signal in the liver. What is the most likely diagnosis?

Accepted Answer

Hepatic cyst

Answer

Hepatic hemangioma

Answer

Hepatocellular carcinoma

Answer

Focal nodular hyperplasia

Question 9

A patient presents with symptoms of bowel obstruction. An abdominal X-ray shows multiple air-fluid levels. Which of the following additional imaging studies is most appropriate to determine the cause?

Accepted Answer

CT scan of the abdomen and pelvis

Answer

MRI of the abdomen

Answer

Barium enema

Answer

Ultrasound of the abdomen

Question 10

What is the imaging finding of barium studies in Crohn's disease?

Accepted Answer

String sign

Answer

Apple core lesion

Answer

Bird beak sign

Answer

Coiled spring appearance

Abdominal and Pelvic Radiology — MCQs

Abdominal and Pelvic Radiology — MCQs

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