Understanding Ultrasound Artefacts in Veterinary Practice

About This Series

This article is part of a three‑part blog series on veterinary ultrasound CPD.

• Part 1: Choosing the Right Ultrasound Transducer

• Part 2: Understanding Ultrasound Artefacts in Veterinary Practice

• Part 3: From Physics to Practice – Applying Ultrasound Skills in Veterinary Clinics

Introduction

Every ultrasound exam produces artefacts. They’re not mistakes, they’re predictable distortions caused by the physics of sound waves. Recognising them is essential to avoid misdiagnosis and, in some cases, to use them diagnostically.

Common Artefacts

• Mirror image artefact – Duplication of structures across strong reflectors. Reflections between structures can produce duplicated images. These mirrored echoes may look like real anatomy but disappear when the probe is repositioned.

  

  Mirror image artefact of the gallbladder. The highly reflective diaphragm creates a duplicated, inverted appearance of the gallbladder deep to the true structure, mimicking an additional fluid-filled cavity.

Clinical tip: By moving the transducer, the mirrored structure will disappear but the original structure will remain.

• Reverberation – Multiple echoes bouncing between interfaces, creating false lines or patterns. When sound waves bounce repeatedly between two surfaces, the machine records multiple echoes. On the image, this shows up as parallel lines, sometimes mimicking extra structures. It’s common in areas with layered tissues or air pockets. You’ll often see reverberation when scanning gas‑filled bowel loops, where the gas–soft tissue interface produces bright, repeating lines. It also appears as A‑lines beneath the pleural surface when assessing for pneumothorax, and during ultrasound‑guided procedures, where the needle shaft can generate multiple parallel echoes that extend deeper than the actual needle.

  
  

  

  A-lines are an example of long-path reverberation artefacts that appear as horizontal, echogenic (bright) lines situated at equidistant intervals below the pleural line. They indicate the presence of normally aerated lung tissue, where the air acts as a strong reflector for ultrasound waves.

  
  
  
  

• Enhancement – Increased brightness behind fluid-filled regions. Tissues with low acoustic resistance, like fluid‑filled spaces, can amplify brightness beneath them. For example, the bladder or blood vessels may cause enhanced echoes that highlight deeper anatomy. Classic examples include the urinary bladder, where the anechoic fluid creates a bright “window” beneath it, and the gallbladder, which enhances the appearance of deeper liver tissue. You’ll also see strong enhancement behind simple cysts in organs such as the kidney or liver, helping distinguish them from solid masses.

  
  

  

  Example of acoustic enhancement artefact, also known as posterior enhancement or increased through-transmission, is a sonographic phenomenon where tissues located deep to a low-attenuating structure appear brighter (hyperechoic) than adjacent tissues at the same depth.

  
  
  
  

• Acoustic shadowing – Dark areas behind dense structures like bone or calculi. Dense structures such as bone or calculi block sound waves, creating a dark shadow behind them. This loss of signal can obscure deeper anatomy but also helps identify the presence of highly attenuating material. Common examples include renal or ureteral calculi, which produce a sharp, clean shadow that confirms their mineral density. Gallstones create a similar shadowing pattern, often paired with a bright anterior wall echo. Even normal ribs generate strong acoustic shadows during thoracic scanning, limiting the field of view but providing predictable landmarks.

Ultrasound image of the urinary bladder showing hyperechoic calculi with distinct acoustic shadowing. The dense mineral content blocks the ultrasound beam, creating a clean, dark shadow that confirms the presence of uroliths.

Why Artefacts Matter

Artefacts can mislead, but they can also confirm diagnoses:

• Mistaking reverberation for pathology can lead to unnecessary interventions.

• Recognising shadowing can confirm calculi.

• Enhancement can highlight fluid collections that might otherwise be missed.

Key Takeaway: Artifacts are an inevitable part of ultrasound imaging. Recognising their causes and appearances is essential for accurate interpretation. Clinicians can minimise their impact by adjusting probe position, gain, and frequency settings, and by selecting the most appropriate probe for the exam. Learning how to adjust these variables in real time is a skill that comes with practice, and each step you take strengthens your ability to deliver high‑quality, evidence‑based care. If you’re ready to take the next step in mastering ultrasound interpretation, our CPD courses provide hands‑on, clinically focused training.

• <<< Read Part 1: Choosing the Right Ultrasound Transducer

• >>> Read Part 3: From Physics to Practice – Applying Ultrasound Skills in Veterinary Clinics