Category: Podcasts

Case of the Week: Perihilar Cholangiocarcinoma/Klatskin Tumor (CT & MRI)

In this radiology lecture, we discuss the CT and MRI appearance of perihilar cholangiocarcinoma.

Key points include:

  • Perihilar cholangiocarcinoma (AKA Klatskin tumor) occurs at bifurcation of the hepatic duct.
  • Cholangiocarcinoma (CC) is a primary malignant tumor of bile duct epithelium, usually adenocarcinoma.
  • CC is the most common primary hepatic malignancy after hepatocellular carcinoma (HCC), and most are extrahepatic (as opposed to intrahepatic).
  • Appearance of CC is based on growth pattern: Mass-forming, periductal infiltrating, and intraductal growing.
  • Risk factors: Parasite infection, choledochal cyst, primary sclerosing cholangitis, recurrent pyogenic cholangitis, and inflammatory bowel disease (ulcerative colitis).
  • Patients are usually 65 or older.
  • On CT and MRI, perihilar CC appears as a biliary stricture with shouldering/abrupt tapering.
  • If a mass is visible, will typically have rimlike enhancement with gradual centripetal enhancement on delayed images, be T2 bright (but not as homogeneous or as bright as hemangioma), and may have a targetlike appearance on DWI (favors CC over HCC).

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Case of the Week: Medullary Sponge Kidney (Ultrasound & CT)

Join me in this radiology lecture revealing the ultrasound and CT appearance of medullary sponge kidney (MSK).

Key points include:

  • MSK is a developmental ectasia with cystic dilatation of the collecting tubules in the pyramids leading to medullary nephrocalcinosis.
  • DDx medullary nephrocalcinosis: Hyperparathyroidism (most common cause in adults), renal tubular acidosis (type 1), MSK, hypervitaminosis D, other causes of hypercalcemia, sarcoidosis.
  • MSK associations: Beckwith-Wiedemann syndrome, congenital hemihypertrophy, Caroli disease, Ehlers-Danlos syndrome.
  • US: Echogenic medullary pyramids.
  • CT: Renal calculi, striated nephrogram, excretory phase “paintbrush” appearance or “growing calculus” sign.
  • Often asymptomatic but may present due to renal stones.

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Case of the Week: Amebic Liver Abscess (Ultrasound & CT)

In this radiology lecture, we discuss the ultrasound and CT appearance of amebic liver abscess.

Key points include:

  • Entamoeba histolytica infection.
  • Endemic in Africa, Southeast Asia, and Central & South America.
  • More common in males.
  • Presents as right upper quadrant pain, fever and hepatomegaly.
  • Both amebic and pyogenic (bacterial) abscesses can have a layered wall with the “double target” or “double rim” sign.
  • Amebic more likely to be unilocular (septations present in 30%) without “cluster” sign typical of multiloculated pyogenic abscess.
  • Amebic more likely solitary, pyogenic more likely multiple.
  • Can be treated medically (metronidazole), but if diagnosis uncertain, if there is failed response to medical therapy, or if large abscess at risk for rupture = aspiration.

Bächler P, Baladron MJ, Menias C, et al. Multimodality Imaging of Liver Infections: Differential Diagnosis and Potential Pitfalls. RadioGraphics 2016 36:4, 1001-1023.

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Case of the Week: Pulmonary Infarction (X-ray & CT)

In this radiology lecture, we discuss the chest x-ray and CT appearance of pulmonary infarction in the setting of acute pulmonary embolism.

Key points include:

  • Uncommon complication of pulmonary embolism.
  • Most common in right lung.
  • Risk of infarction increases with large clot burden.
  • Typically wedge-shaped, peripheral consolidation with no air bronchograms (Hampton hump).
  • However, may not be wedge-shaped, and not all wedge-shaped opacities will be infarcts in the setting of pulmonary embolism.
  • “Bubbly” consolidation containing rounded, central lucencies: Most specific finding of infarct* and represents a combination of infarcted, necrotic lung and adjacent viable, aerated lung.
  • “Vessel” sign: Enlarged vessel leading to apex of a wedge-shaped opacity. Vessel is dilated due to the presence of intraluminal thrombus or distal obstruction.

*Revel MP, Triki R, Chatellier G, et al. Is it possible to recognize pulmonary infarction on multisection CT images? Radiology. 2007;244(3):875-882.

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Case of the Week: Ruptured Ectopic Pregnancy (Ultrasound)

In this radiology lecture, we discuss the ultrasound appearance of ruptured ectopic pregnancy.

Key points include:

  • Most ectopic pregnancies occur in the fallopian tube: Ampulla most common, followed by isthmus and fimbria.
  • Risk factors: Prior ectopic pregnancy, prior surgery (fallopian tube), pelvic inflammatory disease, endometriosis, IVF.
  • “A single measurement of hCG, regardless of its level, does not reliably distinguish between ectopic and intrauterine pregnancy (viable or nonviable).”*
  • Levels of hCG in ectopic pregnancies are highly variable.
  • Tubal rupture main complication, occurs in up to 20%.
  • Free fluid in pelvis alone nonspecific, but echogenic fluid in Morison pouch (subhepatic space) and cul-de-sac raises concern for rupture.
  • Rupture is a relative contraindication to methotrexate (medical) therapy.

*Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med 2013;369:1443-51.

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Case of the Week: Gallstone Ileus (X-ray & CT)

In this radiology lecture, we discuss the appearance of gallstone ileus on x-ray and CT.

Key points include:

  • Gallstone ileus is a rare complication of chronic cholecystitis.
  • Actually not an ileus, but a small bowel obstruction.
  • Gallstone migrates through a fistula between gallbladder and small bowel (usually duodenum) and becomes impacted in the terminal ileum.
  • Stone can also impact in the proximal ileum, jejunum, even in the duodenum/distal stomach causing gastric outlet obstruction (Bouveret syndrome).
  • Rigler triad on abdominal x-ray: Small bowel obstruction, pneumobilia and gallstone in the right iliac fossa.
  • Usually affects the elderly and treated surgically.

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Case of the Week: Testicular Epidermoid Cyst (Ultrasound)

In this radiology lecture, we discuss the ultrasound appearance of testicular epidermoid cyst.

Key points include:

  • Testicular epidermoid cyst is a rare, benign, intratesticular neoplasm.
  • Most common in 2nd-4th decades, typically presents as a painless mass.
  • Lamellated, onion-like, bull’s-eye appearance: Alternating hyperechoic and hypoechoic concentric rings.
  • Appearance secondary to cyst filled with layers of keratin and lined with keratinizing squamous epithelium.
  • Non-vascular and sharply marginated.
  • Nonenhancing on MRI.
  • Important to recognize preoperatively because may be treated with conservative surgery.
  • Management somewhat controversial as originally diagnosed with orchiectomy.
  • Increasingly treated with enucleation if frozen sections of mass are consistent and tumor markers are negative.

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Case of the Week: Necrotizing Pancreatitis (CT & MRI)

In this radiology lecture, we discuss the imaging appearance of necrotizing pancreatitis on both CT and MRI.

Key points include:

  • According to the revised Atlanta classification, there are two types of acute pancreatitis: Interstitial edematous pancreatitis (IEP) and necrotizing pancreatitis (NP).
  • For IEP, fluid collection in first 4 weeks = acute peripancreatic fluid collection, after 4 weeks = pseudocyst.
  • For NP, fluid collection in first 4 weeks = acute necrotic collection, after 4 weeks = walled-off necrosis.
  • Non-enhancing hypoattenuating areas = necrotizing pancreatitis.
  • Gas suspicious for infection/emphysematous pancreatitis.
  • Vascular complications are important to identify.
  • Venous thrombosis: splenic, portal, and mesenteric veins.
  • Pseudoaneurysms: Splenic and gastroduodenal artery.

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Case of the Week: Duplicated Collecting System (VCUG & Ultrasound)

In this radiology lecture, we discuss the imaging appearance of duplicated collecting system and ureterocele, with attention to US and VCUG.

Key points include:

  • Weigert-Meyer rule: Remember the mnemonic “DUMI.”
  • With duplex kidneys and complete ureteral Duplication, ureter draining Upper pole inserts ectopically into bladder Medially and Inferiorly to ureter draining lower pole.
  • Lower pole moiety inserts orthotopically.
  • Upper pole moiety often ends as an ectopic ureterocele.
  • Upper pole moiety tends to obstruct, and lower pole moiety is prone to reflux.
  • Obstructed upper pole moiety causes mass effect with resultant inferior displacement of the lower pole moiety and the “drooping lily” sign.

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Case of the Week: Colonic Lymphoma (CT & PET)

In this radiology lecture, we discuss the imaging appearance of large bowel lymphoma.

Key points include:

  • Often isodense to skeletal muscle.
  • May have aneurysmal dilatation of involved bowel.
  • Less likely obstructive and longer segment involvement compared to colonic adenocarcinoma.
  • Located near ileocecal valve.
  • GI lymphoma: Most common in stomach, followed by small bowel (ileum, jejunum, duodenum), least common site colorectal.
  • Splenomegaly and severe lymphadenopathy favor lymphoma but may not be present.

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