The craniocaudal diameter of the right lobe of the liver is measured at the midclavicular line. This is the most widely accepted clinical standard for identifying hepatomegaly.
Why right lobe?
The right lobe is chosen because it is much larger than the left lobe. It is about five to six times bigger, so it better represents the overall liver size.
Changes in liver size are easier to detect in the right lobe.
The right lobe also has clear anatomical landmarks. The right hemidiaphragm and the inferior tip are easy to see.
These landmarks can be visualized well in a single longitudinal view.
The left lobe has an irregular shape and is harder to measure accurately.
The midclavicular line is an imaginary vertical line drawn from the midpoint of the collarbone. It is used as a standard reference for measuring liver length.
Measuring at the midclavicular line ensures consistency.
This allows different sonographers to measure the liver at the same location every time.
Technique to Measure Cranio-Caudal (CC) Length of Liver
First, position the patient correctly.
The patient should lie in a supine position, flat on their back.
Ask the patient to raise the right arm above the head.
This widens the intercostal spaces.
It helps you see the liver dome more clearly.
Always take measurements during a deep inspiratory breath-hold.
Deep inspiration pushes the liver downward.
This makes the diaphragm and the inferior tip of the liver easier to see on the screen.
Next, choose the correct probe.
Use a curved or convex transducer with a frequency of 2 to 5 MHz.
This probe gives good penetration and a wide field of view.
Place the probe in a longitudinal, or sagittal, orientation.
Align the probe exactly along the right midclavicular line.
Correct alignment is essential for accurate liver length measurement.
Once the liver is visualized in the sagittal plane at the midclavicular line, begin by identifying key landmarks.
First, identify the diaphragm.
It appears as a bright, curved echogenic line at the top of the image.
Next, visualize the inferior tip of the right lobe of the liver.
Make sure the entire liver, from the dome to the tip, is included in one image.
You may need to gently rock the probe to achieve this view.
Measure the craniocaudal length in a straight vertical line.
Start from the dome of the liver just below the diaphragm..
Always use electronic calipers.
Place them from outer margin to outer margin, capsule to capsule.
Do not measure in an oblique or angled plane.
The measurement must be taken in a true sagittal plane.
Sometimes, the ultrasound window is too narrow.
You may not see both the diaphragmatic surface and the inferior tip on the screen at the same time.
In this situation, estimate as accurately as possible where the unseen edge would end.
Place your calipers based on your best anatomical judgment.
Normal Liver Size by Age
Liver size increases with height and body surface area and decreases with age.
| Age Group | Normal Range (MCL) | Typical Average |
| Newborn (0–1 month) | 5.0 – 6.5 cm | 5.7 cm |
| Infant (1–12 months) | 6.5 – 8.0 cm | 7.5 cm |
| Child (1–5 years) | 7.5 – 10.0 cm | 8.8 cm |
| School Age (6–12 years) | 9.0 – 12.5 cm | 11.0 cm |
| Adolescent (13–18 years) | 10.0 – 14.5 cm | 13.5 cm |
| Adult Female | 12.0 – 14.5 cm | 13.5 cm |
| Adult Male | 13.5 – 15.5 cm | 14.5 cm |
Hepatomegaly
A liver span >16.0 cm is widely accepted as hepatomegaly. Measurements between 15.5 cm and 16.0 cm are often considered “borderline enlarged” and are interpreted based on the patient’s body size.
Hepatomegaly Criteria in Pediatric
| Age Group | Upper Limit (95th Percentile) |
| Newborn (0–3 months) | > 8.0 – 8.5 cm |
| Infant (6–12 months) | > 9.5 – 10.0 cm |
| Child (2–6 years) | > 11.0 – 12.0 cm |
| School Age (8–12 years) | > 12.5 – 13.0 cm |
| Adolescent (14–16 years) | > 13.5 – 14.0 cm |
Indirect Ultrasound Signs of Hepatomegaly
Indirect ultrasound signs are morphological clues that suggest liver enlargement.
These are quick visual checks.
You can think of them as a ninja technique to decide if the liver is enlarged.
First, look at how far the liver extends past the right kidney.
Normally, the right lobe does not extend much beyond the lower pole of the right kidney.
It usually ends around halfway down the kidney.
If the liver extends clearly below this level, hepatomegaly should be suspected. Next, observe the inferior edge of the liver.
A normal liver has a sharp and pointed inferior border.
If the edge looks rounded or blunted, it often indicates liver swelling.
Cause of Hepatomegaly
- Fatty Liver/ Metabolic dysfunction-associated steatotic liver disease
- Alcohol-Related Liver Disease (ALD)
- Infections and Inflammation: viral hepatitis, infectious mononucleosis, liver abscess
- Storage disorder : glycogen storage disease, hemochromatosis , wilson’s disease
- Primary Liver Cancer: Hepatocellular carcinoma or cholangiocarcinoma.
- Metastatic Cancer: Most common malignant cause; cancer spreading from the colon, breast, or lung
- Congestive hepatopathy (right sided heart failure, budd-chiari syndrome
- Toxic and Drug-Induced Injury
- Medication Overdose: Common with acetaminophen (Tylenol).
- Herbal Supplements: Certain products like kava, black cohosh, and valerian root are linked to liver injury.
Riedel’s Lobe: A Mimicker of Hepatomegaly
Riedel’s lobe is a common normal anatomical variant.
It appears as a tongue like downward projection of the right lobe of the liver.
Because it extends inferiorly, it can mimic hepatomegaly.
It is not a true accessory lobe. It is simply a shape variation of the existing right lobe.
Riedel’s lobe is much more common in females.
The female to male ratio is about three to one. Reported prevalence varies widely.
It is seen in about 3.3 percent to 31 percent of the population.
The exact cause is debated.
It may be congenital due to abnormal development of the hepatic bud.
It may also be acquired. Chronic inflammation or traction from gallbladder disease may play a role.
On ultrasound, Riedel’s lobe is often mistaken for hepatomegaly or an abdominal mass.
To differentiate it from true liver disease, look for key features.
The inferior edge remains sharp and pointed.
This is unlike true hepatomegaly, where the edge is rounded or blunted.
The echotexture of Riedel’s lobe is normal.
It looks identical to the rest of the liver parenchyma.
The left lobe is usually normal in size.
In true hepatomegaly, the entire liver is typically enlarged.
Clinically, Riedel’s lobe may be felt as a mass in the right lower abdomen.
This can lead to unnecessary investigations if it is not recognized.
In rare cases, the lobe can twist on itself, causing acute abdominal pain.
It may also cause mild discomfort by pressing on nearby organs such as the stomach or kidney.