Article

Total abdominal ultrasound: protocol and images

Complete total abdominal ultrasound protocol: preparation, systematic organ-by-organ sweep, mandatory images, normal report, limitations and pitfalls.

What it is and when to indicate it

Total abdominal ultrasound systematically assesses the abdominal viscera and the retroperitoneum: liver, gallbladder and bile ducts, pancreas, spleen, both kidneys, aorta, inferior vena cava, bladder and the accessible portions of the gastrointestinal tract. It is a first-line exam for abdominal pain, altered liver or renal function, aortic aneurysm screening, fever of unknown origin and follow-up of known findings.

This page is an educational bridge that organizes the protocol in clear language. It does not replace the original guidelines (ACR-AIUM-SPR-SRU, AIUM, CBR), supervised training or clinical correlation. The goal is a complete, reproducible sweep and a report that states what was seen and what was limited.

Preparation and image optimization

Preparation improves image quality, but clinical urgency takes priority: an acute abdomen does not wait for fasting. When elective, advise:

• Fasting of 6 to 8 hours to reduce gas and distend the gallbladder
• Comfortably full bladder when the focus includes the pelvis/bladder
• Low-frequency curved transducer (2 to 5 MHz); high-frequency linear for the wall and superficial structures
• Abdominal preset, focus at target depth, gain and TGC adjusted, harmonic and compounding to reduce noise
• Maneuvers: deep inspiration, right and left lateral decubitus, and graded compression to displace gas

Systematic sweep: a fixed route

Always follow the same sequence so structures are not missed. A consistent route reduces error and speeds up the exam with practice. Document each organ in at least two planes (longitudinal and transverse) and record measurements when relevant.

• Liver: right and left lobes, echotexture, contours, hepatic and portal veins, right lobe measurement
• Gallbladder: walls, content, mobile stones, sonographic Murphy sign; bile ducts and common bile duct caliber
• Pancreas: head, body and tail using the stomach/spleen as a window; pancreatic duct
• Spleen: long-axis dimension, homogeneous echotexture
• Right and left kidney: dimensions, parenchymal thickness, corticomedullary differentiation, no pelvicalyceal dilation
• Aorta and inferior vena cava: aortic caliber at three levels; IVC and its respiratory variation
• Bladder: filling, walls, content; post-void residual when indicated
• Retroperitoneum, bowel loops, adrenals and gutters: search for lymphadenopathy, free fluid and collections

Useful measurements and reference values

Reference values vary with body habitus, age and equipment; use them as a guide, not as a rigid cutoff, and always with clinical correlation.

• Liver: right lobe at the midclavicular line usually up to about 15 to 16 cm
• Common bile duct: usually up to 6 to 7 mm, with a physiological increase after cholecystectomy and with age
• Gallbladder: thin wall, typically up to 3 mm when distended
• Spleen: long axis usually up to about 12 cm
• Kidneys: about 9 to 12 cm in length, with symmetric parenchyma
• Abdominal aorta: a diameter above 3 cm defines an aneurysm

Mandatory images (documentation)

Documentation proves the sweep and allows future comparison. A typical minimum set includes:

• Liver in two planes, with hepatic and portal veins, and the hepatorenal interface
• Gallbladder in two planes and the common bile duct with measurement
• Transverse pancreas and spleen at its long axis
• Each kidney in longitudinal and transverse planes, with measurement
• Aorta in longitudinal and transverse planes, and the IVC
• Bladder in two planes; any focal finding documented in two planes with measurement

Normal report template

The normal report should be specific enough to prove that each structure was assessed, without padding with generic text. Example structure:

• Liver of normal dimensions, regular contours and homogeneous echotexture, without focal lesions
• Gallbladder with thin walls, without stones or thickening; non-dilated bile ducts
• Pancreas and spleen without alterations; spleen of normal dimensions
• Kidneys in topical position, of preserved dimensions and parenchyma, without pelvicalyceal dilation or stones
• Aorta of normal caliber, without aneurysmal dilation; IVC without alterations
• Bladder with thin walls and anechoic content; no free fluid and no lymphadenopathy

Technical limitations: report them honestly

When something could not be well assessed, the report must say so, without vague terms. This protects the patient and the examiner and guides the next step.

• Bowel gas limiting the pancreas and loops
• Body habitus/obesity reducing penetration and resolution
• Inadequate fasting with a contracted gallbladder, hampering wall assessment
• Empty bladder limiting the pelvic assessment
• Suggestion of a complementary method (new window, return fasting, CT/MRI) when indicated

Common pitfalls and how to avoid them

• Mistaking a loop for fluid or a collection: confirm with peristalsis and orthogonal planes
• Gas shadow simulating a stone: reposition and use decubitus positions
• Slightly enlarged common bile duct after cholecystectomy or with age: interpret in context
• Overvalued simple renal/hepatic cysts: apply criteria (thin walls, anechoic, posterior enhancement)
• Riedel lobe and anatomical variants mistaken for hepatomegaly
• Measuring in an oblique plane, overestimating dimensions

First pathological findings to recognize

• Hepatic steatosis (hyperechoic liver with posterior attenuation)
• Cholelithiasis and signs of cholecystitis (thickened wall, pericholecystic fluid, sonographic Murphy)
• Bile duct dilation suggesting obstruction
• Hydronephrosis and renal stones with acoustic shadowing
• Abdominal aortic aneurysm (diameter above 3 cm)
• Free fluid, collections and lymphadenopathy

Do not overdiagnose

Ultrasound is operator-dependent and dynamic. The conclusion should be proportional to the finding and preserve clinical correlation: describe well what is seen, avoid definitive labels on doubtful images, and recommend further workup when the doubt is clinically relevant. A measurement without context creates false precision.

Sources

Educational content; it does not replace original guidelines, medical evaluation or supervised training. Main references:

• ACR-AIUM-SPR-SRU. Practice Parameter for the Performance of an Ultrasound Examination of the Abdomen and/or Retroperitoneum.
• AIUM. Practice Parameter for the Performance of an Ultrasound Examination of the Abdomen and/or Retroperitoneum.
• Brazilian College of Radiology (CBR). Standardization and technical guidelines for ultrasound.
• Rumack CM, Levine D. Diagnostic Ultrasound (reference for abdominal anatomy and technique).
• Radiopaedia. Abdominal ultrasound (didactic support, not copied).

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