ARDMS AB-Abdomen - Abdomen Sonography Examination

Tissue harmonic imaging significantly reduces reverberation and side-lobe artifacts by utilizing nonlinear propagation of ultrasound waves. This produces clearer images of fluid-filled structures like the gallbladder, improving visualization of wall thickness and intraluminal contents.

According to Zwiebel’s Introduction to Vascular Ultrasound:

“Harmonic imaging effectively reduces reverberation artifact, improving image quality in gallbladder and cystic structure evaluation.”

The ultrasound image demonstrates a tubular, non-compressible, blind-ending structure located in the right lower quadrant (RLQ) with associated echogenic periappendiceal fat and possibly adjacent fluid or phlegmon. These features are consistent with appendicitis. Given the clinical history of fever and RLQ pain, along with the irregular borders and complex periappendiceal findings, the diagnosis of a ruptured appendix is most likely.

Key sonographic features of ruptured appendicitis include:

Non-visualization or distortion of the normal appendiceal wall architecture

Periappendiceal fluid collection or abscess

Disruption of the echogenic submucosal layer

Surrounding fat stranding (hyperechoic inflammatory changes)

Clinical correlation with fever and peritonitis

Comparison of answer choices:

A. Bowel obstruction typically shows dilated bowel loops with air-fluid levels, not a tubular structure like the appendix.

B. Intussusception presents with a target or “donut” sign in a transverse view, not a linear tubular structure.

C. Enlarged lymph nodes are usually round or oval and hypoechoic with a central echogenic hilum, without a tubular appearance.

D. Ruptured appendix — Correct. The ultrasound features and clinical presentation match.

The ultrasound image shows echogenic foci with dirty shadowing and reverberation artifacts within the gallbladder wall and lumen. These features are characteristic of emphysematous cholecystitis, a severe, life-threatening variant of acute cholecystitis caused by gas-forming organisms (e.g., Clostridium or E. coli) infecting the gallbladder wall.

Sonographic features of emphysematous cholecystitis:

Echogenic gas within the gallbladder wall or lumen

Reverberation or "dirty" shadowing artifacts

May show intramural gas bubbles or "ring-down" artifact

Often seen in diabetic or immunocompromised patients

No gallstones may be present ("acalculous cholecystitis")

Clinical context:

More common in elderly men and diabetics

Presents with right upper quadrant pain, fever, and leukocytosis

Surgical emergency due to risk of perforation and sepsis

Differentiation from other options:

A. Adenomyomatosis: Involves gallbladder wall thickening with “comet tail” artifacts due to Rokitansky-Aschoff sinuses, not intramural gas.

B. Porcelain gallbladder: Shows curvilinear calcification of the gallbladder wall — dense echogenic rim with posterior shadowing.

C. Gangrenous cholecystitis: May show wall irregularity, intraluminal membranes, and absence of Doppler flow but lacks intramural gas.

The ultrasound image of the thyroid clearly shows posterior shadowing originating from the lateral edges of a rounded structure, which is indicative of edge shadow artifact. Edge shadowing occurs when an ultrasound beam passes tangentially to a rounded or curved structure, such as a cyst or blood vessel. The difference in sound wave refraction and beam divergence at the edges leads to decreased echo signals deep to the edges, creating linear hypoechoic bands — which is exactly what the arrows are pointing to in the image.

Edge shadow artifact is purely a result of beam physics and not a real anatomic or pathologic finding.

Key characteristics of edge shadowing:

Appears as a narrow, linear hypoechoic (dark) shadow extending deep to the edge of a curved interface (e.g., cyst, vessel, thyroid nodule)

Caused by refraction and beam deflection, leading to reduced beam intensity distal to the edges

Most commonly seen adjacent to cysts or fluid-filled structures

Differentiation from other options:

A. Focal enhancement: Appears as increased echogenicity distal to a fluid-filled structure due to lower attenuation of the sound beam through fluid (opposite of shadowing).

C. Speed error: A less common artifact that results in displacement of structures due to variation in assumed sound speed.

D. Comet tail: A reverberation artifact that appears as a series of closely spaced bright echoes, often associated with metallic objects or cholesterol crystals in adenomyomatosis.

Transudative pleural effusions result from imbalances in hydrostatic and oncotic pressures, most commonly caused by congestive heart failure (CHF). In CHF, elevated hydrostatic pressure in the pulmonary capillaries leads to fluid leakage into the pleural space without significant protein or cellular content (hence, transudate). Exudative effusions (associated with infections, malignancy, and inflammation) are more often seen with pulmonary emboli, lymphoma, or empyema.

According to Light’s criteria (which differentiates transudates from exudates):

"Congestive heart failure remains the leading cause of transudative pleural effusions." (Light RW. Pleural Diseases, 6th ed.).

An accessory spleen (splenule) is a congenital variant, commonly located near the splenic hilum, and has identical echogenicity to the native spleen. This finding is benign and often incidental.

According to Rumack’s Diagnostic Ultrasound:

“Accessory spleens are typically found near the splenic hilum and are isoechoic to the normal splenic parenchyma.”

Most thyroid cancer recurrences are found in the ipsilateral neck—particularly in the central (level VI) or lateral (levels II-V) compartments on the same side as the original malignancy.

According to AIUM Practice Parameters:

“Post-thyroidectomy recurrence most frequently occurs ipsilateral to the original tumor, commonly involving regional lymph nodes.”

A tumor (such as cholangiocarcinoma, pancreatic head carcinoma, or metastases) is a common cause of biliary duct obstruction. It can compress or invade the bile ducts, leading to intrahepatic and extrahepatic duct dilatation.

Cholecystitis (B) typically affects the gallbladder but may rarely cause duct obstruction if complicated.

Pneumobilia (C) refers to air in the biliary tree, not obstruction.

Hepatitis (D) causes liver inflammation but not mechanical biliary obstruction.

Reference Extracts:

Rumack CM, Wilson SR, Charboneau JW, Levine D. Diagnostic Ultrasound. 5th ed. Elsevier, 2017.

Gore RM, Levine MS. Textbook of Gastrointestinal Radiology. 4th ed. Saunders, 2015.

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The ultrasound image shows a classic “target sign” or “donut sign,” characterized by concentric rings of alternating echogenicity. This sonographic finding is pathognomonic for intussusception, particularly when seen in the transverse plane.

Intussusception occurs when a segment of bowel telescopes into an adjacent segment, typically in children aged 6 months to 3 years. It commonly presents with intermittent abdominal pain, vomiting, and sometimes “red currant jelly” stools.

Key ultrasound features of intussusception:

Target sign in transverse view (concentric rings of bowel layers)

Pseudokidney or sandwich sign in longitudinal view

May show intraluminal mesenteric fat or vessels dragged in with the intussusceptum

Comparison of answer choices:

A. Bowel obstruction may show dilated loops of bowel with air-fluid levels and to-and-fro peristalsis but lacks the concentric ring sign.

B. Diverticulitis typically shows bowel wall thickening and pericolic fat stranding; not the concentric target appearance.

C. Appendicitis may appear as a blind-ending tubular structure (>6 mm), not with concentric ring pattern.

D. Intussusception — Correct. The image demonstrates the classic target sign seen with this condition.