Short-Axis Scanning of the Gallbladder by the Right Subcostal Margin

Short-axis gallbladder section • Right subcostal approach • Transverse view

Scanning Method

The patient should preferably be fasted for 8–12 hours and examined initially in the supine position. Place the ultrasound probe below the right subcostal margin in the right upper quadrant. After obtaining the gallbladder in longitudinal section, rotate the transducer approximately 90 degrees to obtain the short-axis or transverse section. Adjust the probe position, angle, depth, gain, and focal zone to demonstrate the gallbladder lumen and wall in cross-section. The short-axis plane is useful for assessing the gallbladder width, wall, lumen, and intraluminal contents.

Key scanning point: Begin from the right subcostal margin and identify the gallbladder. Rotate the probe approximately 90 degrees from the longitudinal orientation to obtain the short-axis view. Optimize the image so that the gallbladder lumen and surrounding wall are clearly demonstrated.

Ultrasound Image

Figure 1.1: Short-axis section of the gallbladder obtained from the right subcostal approach. The transverse plane demonstrates the gallbladder lumen and wall in cross-section and permits assessment of gallbladder contents and wall characteristics.

Anatomical / Scanning Diagram

Figure 1.2: Diagram demonstrating the right subcostal probe orientation, short-axis scanning plane, gallbladder, adjacent liver, and relevant anatomical landmarks.

Section Structure

The principal structures demonstrated in this plane are the gallbladder (GB) in cross-section and the adjacent right lobe of the liver (RL). Depending on the exact scanning level, the short-axis plane may also demonstrate portions of the gallbladder wall, lumen, cystic duct region, portal vein, common hepatic duct, common bile duct, and adjacent bowel. The short-axis view is particularly useful for evaluating the gallbladder wall and measuring its transverse dimension.

Structures to identify

• Right lobe of the liver (RL)
• Gallbladder (GB)
• Gallbladder lumen
• Anterior gallbladder wall
• Posterior gallbladder wall
• Gallbladder fundus/body/neck depending on the level scanned
• Cystic duct when visualized
• Common hepatic duct (CHD) when visualized
• Common bile duct (CBD) when visualized
• Portal vein (PV)
• Adjacent duodenum / bowel

Abbreviations Used in the Figure

Abbreviation	Full form	Identification
GB	Gallbladder	Fluid-filled biliary organ visualized in short-axis section.
RL	Right Lobe of Liver	Adjacent hepatic parenchyma surrounding the gallbladder fossa.
GW	Gallbladder Wall	Echogenic wall surrounding the gallbladder lumen.
GL	Gallbladder Lumen	Anechoic or fluid-containing central portion of the gallbladder.
CHD	Common Hepatic Duct	Biliary structure formed by the right and left hepatic ducts.
CBD	Common Bile Duct	Extrahepatic bile duct when adequately visualized.
PV	Portal Vein	Important vascular landmark adjacent to the biliary structures.

Measuring Method and Normal

The short-axis plane is particularly useful for assessment of the gallbladder width and wall thickness. When clinically indicated, obtain the measurement in a true transverse plane rather than an oblique section. The gallbladder wall should be measured at a clearly visualized segment with the ultrasound beam appropriately oriented.

Measurement	Caliper method	Reference / interpretation
Gallbladder width	Measure the maximum transverse dimension from outer wall to outer wall in the short-axis plane.	Interpret according to gallbladder distension, patient preparation, and the overall sonographic appearance.
Gallbladder wall thickness	Measure the wall at a clearly visualized segment, preferably where the wall is perpendicular to the ultrasound beam.	Document the measurement and assess for focal or diffuse wall thickening.
Luminal contents	Evaluate the lumen for echogenic material, calculi, sludge, masses, or other intraluminal abnormalities.	Assess mobility, posterior acoustic shadowing, and relationship to the gallbladder wall when applicable.

Measurement note: The short-axis plane should be obtained perpendicular to the gallbladder long axis. Avoid oblique measurements and avoid including adjacent liver, pericholecystic fluid, or intraluminal material within the wall measurement.

The Clinical Application Value

The short-axis view provides an important cross-sectional assessment of the gallbladder lumen and wall. It complements the longitudinal view by allowing assessment of the gallbladder's transverse dimension, wall contour, and intraluminal contents. This plane is useful for evaluating gallstones, sludge, wall thickening, focal wall lesions, and other gallbladder abnormalities.

• Demonstration of the gallbladder in short-axis section.
• Assessment of gallbladder transverse diameter.
• Assessment of gallbladder wall thickness.
• Assessment of wall contour and symmetry.
• Evaluation of gallbladder lumen for stones.
• Assessment of posterior acoustic shadowing from calculi.
• Evaluation of biliary sludge.
• Assessment of focal wall lesions or polyps.
• Assessment for pericholecystic fluid.
• Assessment of adjacent hepatic and biliary structures.

Quick Scanning Checklist

1	Fast the patient for 8–12 hours when appropriate.
2	Position the patient supine initially.
3	Place the probe at or just below the right subcostal margin.
4	Identify the gallbladder in longitudinal section first.
5	Rotate the probe approximately 90 degrees to obtain the short-axis plane.
6	Optimize depth, gain, focal zone, and probe pressure.
7	Identify the gallbladder lumen and surrounding wall.
8	Assess the lumen for stones, sludge, and other intraluminal contents.
9	Assess gallbladder wall thickness, contour, and symmetry.
10	Assess the adjacent liver, biliary structures, and pericholecystic region for abnormalities.

Diagnostic Pathology

The short-axis right subcostal view of the gallbladder can assist in identifying gallbladder, biliary, hepatic, and adjacent upper abdominal abnormalities. Evaluate the GB, gallbladder wall, lumen, adjacent liver, and visualized biliary structures for abnormal findings.

Key Sonographic Findings

• Gallbladder wall thickening: Increased wall thickness requiring correlation with gallbladder distension and other sonographic findings.
• Cholelithiasis: Echogenic intraluminal focus or foci with posterior acoustic shadowing and/or mobility when demonstrated.
• Gallbladder sludge: Low-level dependent echoes within the lumen that generally do not produce clean posterior acoustic shadowing.
• Gallbladder distension: Increased gallbladder size or distension in the appropriate clinical context.
• Impacted calculus: A calculus located near the gallbladder neck or cystic duct region may be associated with obstruction-related findings.
• Gallbladder polyp: Focal non-mobile wall-based intraluminal lesion requiring assessment of size and morphology.
• Gallbladder wall irregularity: Focal or diffuse alteration in the normal smooth contour or echotexture of the wall.
• Pericholecystic fluid: Fluid surrounding the gallbladder that may accompany inflammatory or other pathological processes.
• Gallbladder mass: Focal abnormal tissue or irregular wall-based lesion differing from the normal gallbladder wall or lumen contents.
• Inflammatory gallbladder changes: Wall thickening, distension, pericholecystic fluid, tenderness during scanning, or an impacted calculus may occur in the appropriate clinical setting.
• Biliary duct dilatation: Increased caliber of visualized intrahepatic or extrahepatic bile ducts requiring assessment of the biliary system.

Diagnostic note: Abnormal findings should be interpreted together with the complete abdominal ultrasound examination, clinical history, laboratory findings, and additional imaging when indicated. A single sonographic finding should not be used in isolation to establish a diagnosis.

Diagnostic Sonography • Gallbladder

Short-Axis Right Subcostal View