What does an abdominal ultrasound include?

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What Does an Abdominal Ultrasound Include?

An abdominal ultrasound systematically evaluates the solid organs (liver, gallbladder, spleen, pancreas, kidneys) and major vascular structures (abdominal aorta), with assessment for free fluid in the peritoneal cavity. 1, 2

Standard Anatomic Structures Examined

Solid Organs

  • Liver: Evaluated for size, echogenicity, focal lesions, and signs of cirrhosis or fatty infiltration 1, 3
  • Gallbladder: Assessed for stones, wall thickening, pericholecystic fluid, and distension 1, 3
  • Pancreas: Visualized when not obscured by bowel gas, examining for masses, pseudocysts, or inflammatory changes 1, 2
  • Spleen: Evaluated for size and focal lesions 4, 2
  • Kidneys (bilateral): Assessed for hydronephrosis, masses, and size in both short- and long-axis views 1, 2

Vascular Structures

  • Abdominal aorta: Scanned from the diaphragmatic hiatus to the aortic bifurcation in both transverse and longitudinal planes to detect aneurysms (diameter >3.0 cm) 1
  • Portal vein: Evaluated for patency and abnormalities 3

Additional Assessments

  • Free fluid detection: Systematic evaluation of the hepatorenal recess (Morrison's pouch), splenorenal recess, and pelvis for intraperitoneal fluid 1
  • Bladder: Assessed for distension and urine volume 1
  • Common bile duct: Evaluated for dilatation (>6-10 mm) and stones, though sensitivity for CBD stones is limited (22.5-75%) 1, 3

Systematic Examination Technique

The examination follows a standardized approach to ensure complete evaluation 2:

  • Epigastric region first: Initial scanning of the aorta and pancreas
  • Right upper quadrant: Liver, gallbladder, right kidney, and hepatorenal space
  • Left upper quadrant: Spleen, left kidney, and splenorenal space
  • Both iliac fossae: Lower abdominal structures
  • Hypogastric region: Bladder and pelvic free fluid 2

Multiple scanning planes (longitudinal, transverse, and oblique) are used to visualize all structures completely 2.

Clinical Context Matters

The specific focus of the examination varies based on clinical presentation:

  • Trauma patients: FAST examination prioritizes detection of free fluid in the pericardial sac, pleural spaces, and peritoneum 1
  • Jaundice evaluation: Emphasis on biliary tree dilatation, gallbladder pathology, and liver parenchyma 1
  • Acute abdominal pain: Focused assessment of the gallbladder, appendix (when visible), and free fluid 1
  • Suspected AAA: Detailed aortic measurements from diaphragm to bifurcation with assessment for rupture (free fluid) 1

Important Limitations

Technical Factors

  • Bowel gas frequently obscures the pancreas and portions of other organs 1, 4
  • Obesity reduces image quality and penetration 3
  • Operator experience significantly affects diagnostic accuracy, particularly for subtle findings 3, 5

Diagnostic Limitations

  • Cannot reliably detect retroperitoneal hemorrhage even when AAA is present 1
  • Sensitivity drops to 53-65% for mild hepatic steatosis (requires >33% lipid content for reliable detection) 3
  • CBD stones have lower sensitivity (22.5-75%) compared to gallbladder stones (96%) 1, 3
  • Small aneurysms (<3.0 cm) do not exclude rupture risk in symptomatic patients 1

When Ultrasound Is Insufficient

Additional imaging is warranted when 1, 3:

  • Equivocal findings with persistent clinical suspicion require CT or MRI
  • Suspected biliary obstruction with negative ultrasound may need MRCP (85-100% sensitivity)
  • Hepatobiliary scintigraphy serves as the gold standard when ultrasound is inconclusive for acute cholecystitis
  • Technical limitations (gas, obesity, tenderness) prevent adequate visualization

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Guideline

RUQ Ultrasound Indications in Heavy Alcohol Consumers

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

4
Research

Human endoscopic ultrasonography.

Gastroenterology, 1982

5
Research

Feasibility and Diagnostic Accuracy of Point-of-Care Abdominal Sonography by Pocket-Sized Imaging Devices, Performed by Medical Residents.

Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine, 2017

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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