Radiological signs are visual clues on imaging that point toward specific diagnoses. As a medical student, knowing these signs can help you crack exams like NEET PG, INI-CET, NEXT, and even help in clinical diagnosis.
In this blog, we’ll cover the top 10 radiological signs, what they mean, where you’ll see them, and quick tips to remember them
1. Silhouette Sign
Seen In: Chest X-ray
What It Means: Loss of normal borders between structures of the same density (e.g., heart and lung).
Indicates: Lobar pneumonia, especially in the right middle lobe.
🧠 Tip: If the right heart border is obscured, think of right middle lobe involvement.
2. Ground-Glass Opacity
Seen In: CT Chest
What It Means: A hazy area that doesn’t obscure underlying vessels.
Indicates: COVID-19 pneumonia, interstitial lung disease, alveolitis.
🧠 Tip: Remember “GG” = Ground Glass = Ghostly Gray appearance.
3. Double Bubble Sign
Seen In: Abdominal X-ray (neonates)
What It Means: Two round black bubbles (stomach + duodenum).
Indicates: Duodenal atresia.
🧠 Tip: Classic in Down syndrome infants.
4. Air Bronchogram
Seen In: Chest X-ray, CT
What It Means: Air-filled bronchi seen against opaque alveoli.
Indicates: Consolidation (e.g., pneumonia).
🧠 Tip: “Air tubes in white lung” = air bronchogram.
5. Bat Wing Appearance
Seen In: Chest X-ray
What It Means: Bilateral, central alveolar infiltrates.
Indicates: Pulmonary edema.
🧠 Tip: Looks like a bat spreading its wings across both lungs.
6. String Sign of Kantor
Seen In: Barium follow-through
What It Means: Narrow, string-like terminal ileum.
Indicates: Crohn’s disease.
🧠 Tip: Chronic inflammation causes narrowing.
7. Thumb Sign
Seen In: Lateral neck X-ray
What It Means: Enlarged epiglottis resembling a thumb.
Indicates: Acute epiglottitis (especially in children).
🧠 Tip: Think of a “thumbprint” over the airway.
8. Hair-on-End Appearance
Seen In: Skull X-ray
What It Means: Spicules of bone seen perpendicular to the skull.
Indicates: Thalassemia major, sickle cell anemia.
🧠 Tip: Due to marrow hyperplasia.
9. Scottie Dog Sign
Seen In: Oblique lumbar spine X-ray
What It Means: Normal vertebral structures resemble a Scottish terrier.
Indicates: Spondylolysis (when the “neck” is fractured).
🧠 Tip: Use for spotting pars interarticularis defects.
10. Apple Core Lesion
Seen In: Barium enema
What It Means: Narrowing of the colon lumen with overhanging edges.
Indicates: Colorectal carcinoma.
🧠 Tip: Imagine an apple that’s been bitten from both sides.
🧠 Quick Mnemonic for Chest Signs:
“SABG-BAT”
- Silhouette
- Air bronchogram
- Bat wing
- Ground-glass
- Bubbles (Double Bubble)
- Apple core
- Thumb sign
🎯 Final Thoughts
Radiological signs make diagnosis easier and faster — especially when you know what to look for. These 10 signs are high-yield for both exams and clinical practice.
Want to practice with real images? Check out our book or video tutorials for visual reinforcement.
✅ Next Up:
Don’t miss our next blog: How to Read an X-ray Like a Pro: Step-by-Step Guide
📘 Recommended Book: Radiology Made Easy by Bharat Goyal
🎥 Video Lessons: Available on our YouTube channel!