What Is Ultrasound? For Which Diseases Is Ultrasound Used?

Ultrasound is a medical imaging method that uses high-frequency sound waves to visualize soft tissues and organs. It is widely used due to its safety, non-invasiveness, and lack of radiation exposure.

It is commonly applied in obstetrics to monitor fetal development, in abdominal imaging for liver, kidney, and gallbladder evaluation, and in cardiology to assess heart function.

Ultrasound also plays a key role in detecting thyroid nodules, vascular diseases, and musculoskeletal injuries. Doppler ultrasound provides additional information on blood flow and vessel health.

Its advantages include real-time imaging, portability, and affordability. These features make ultrasound a preferred diagnostic tool across multiple specialties in daily medical practice.

What Is Ultrasound and How Does It Work?

You can think of ultrasound as a kind of sonar system. Just as submarines or ships send out sound waves to detect objects underwater and measure their echoes, an ultrasound machine works with a similar mechanism. High-frequency sound waves (typically between 2–20 MHz, far above what the human ear can hear) are sent into the body via a special probe or “transducer.” These waves reflect off tissues of varying density—such as muscle, fat, or bone. The returning echoes are detected by the transducer, and a computer system creates a real-time image on the screen.

The key technology here is the “piezoelectric effect.” Tiny crystals inside the transducer convert electrical energy into mechanical sound waves (ultrasound waves), and then convert the returning sound waves back into electrical signals. In simple terms, you can think of it as “sending sound with a microphone and mapping the inside of the body based on the returning echoes.”

Ultrasound’s resolution and depth perception depend on the frequency used. Higher frequencies (like 10–15 MHz) are great for viewing superficial tissues—skin, muscles, tendons, or the thyroid. However, high frequencies do not penetrate deeply. Lower frequencies (like 2–5 MHz) are used to examine deeper areas—such as the liver or kidneys. Basically, the lower the frequency, the deeper the penetration but the lower the image detail; the higher the frequency, the less depth but the greater the detail.

There is also the concept of Doppler ultrasound, which is ideal for assessing blood flow. When we want information about the speed and direction of blood within vessels, we use Doppler techniques. Just as a moving train’s whistle changes pitch as it approaches and then moves away (the Doppler effect), ultrasound uses a similar principle to analyze blood cell movement. This provides detailed information about everything from leg vein clots to heart valve function.

One of ultrasound’s greatest advantages is that it does not use radiation. Unlike X-ray or CT, there is no ionizing radiation; only sound waves are used, making it extremely safe—especially for pregnant women, children, and patients needing frequent imaging.

How Is Ultrasound Used in Pregnancy?

Ultrasound is one of the safest and most effective ways to monitor the health and development of a baby in the womb, as well as the structural features of the uterus during pregnancy. The absence of radiation makes it the first choice for pregnant women. In early pregnancy, transvaginal ultrasound may be used for a clearer view, especially when the baby is still very small and cannot be seen well via the abdomen. For example, it can help detect whether the pregnancy is in the uterus or an ectopic pregnancy.

In later weeks, transabdominal ultrasound allows clear visualization of the baby’s overall development, organ structure, amniotic fluid, and even facial features. It’s like “watching a fish underwater by observing the waves it creates.” By checking the development of the baby’s organs, heart, brain, and spinal cord, the health of both mother and baby can be comprehensively evaluated.

Doppler ultrasound is also frequently used during pregnancy. It can assess blood flow between the placenta and baby, umbilical cord vessels, and blood circulation in the baby’s brain. This allows early detection of issues such as growth retardation or placenta previa. Early diagnosis is invaluable for both mother and baby, enabling timely medical intervention and closer monitoring of the pregnancy.

In special cases, procedures such as amniocentesis (sampling the fluid around the baby) or chorionic villus sampling (biopsy of placenta tissue) can be performed under ultrasound guidance for genetic testing. Here, ultrasound serves as a “guide,” allowing the doctor to take samples in the safest way.

One of the most joyful parts is that parents can see their baby on the screen and even watch the heartbeat before birth. This is emotionally significant and strengthens the bond with the baby. It’s clear that ultrasound is extremely important for pregnancy follow-up, offering both medical and psychological benefits.

Which Gynecological Diseases Can Ultrasound Diagnose?

Ultrasound is extremely useful for detecting structural and functional disorders of the female reproductive organs. It provides detailed information about the uterus, ovaries, and surrounding pelvic areas. Think of it as a “window” through which you can observe the inside of the uterus and ovaries.

• Uterine Fibroids: Benign tumors originating from the uterine wall. Ultrasound reveals their location, size, and impact on the uterine cavity, helping decide whether monitoring or surgery is needed.
• Ovarian Cysts: Fluid-filled sacs within the ovaries, commonly seen. Ultrasound shows the size and structure (fluid, solid, or mixed) of cysts, and color Doppler can help assess malignancy risk.
• Endometriosis: Tissue similar to the uterine lining found outside the uterus. Endometriomas (“chocolate cysts”) usually appear as dense, coffee-ground-like images on ultrasound.
• Ectopic Pregnancy: Pregnancy occurring outside the uterus (usually in the fallopian tube) is life-threatening. Transvaginal ultrasound can identify this early.
• Pelvic Inflammatory Disease (PID): Infection of the uterus, tubes, and surrounding tissues. Ultrasound can detect inflammatory fluid or abscesses.
• Endometrial Polyps: Polyps in the uterine lining may cause bleeding. Transvaginal ultrasound gives detailed information about their presence.
• Congenital Uterine Anomalies: Anatomical differences (such as septate or bicornuate uterus) that can cause infertility or miscarriage can be visualized by ultrasound.

Which Internal Organs Are Evaluated by Ultrasound?

One of the most common uses of ultrasound is for the evaluation of abdominal organs: liver, gallbladder, spleen, kidneys, and pancreas are often examined with this method. The bladder and, to some extent, the intestines can also be visualized, though bowel gas can lower image quality. Blood vessels (like the aorta or main veins) can also be evaluated for dilation, blockage, or aneurysm.

• Liver and Gallbladder: Stones, sludge, and polyps in the gallbladder; liver size, tissue structure, cysts, or tumors; fatty liver or cirrhosis can all be assessed. It’s ideal for chronic liver disease follow-up.
• Kidneys: Detects stones, dilation of urinary channels, and kidney cysts. Also monitors kidney size changes and is common for recurrent pain or infection cases.
• Pancreas: While deep behind the stomach and often better seen with CT or MRI, ultrasound can detect mass or inflammation, especially in the head and body. It’s used for suspected acute pancreatitis or to check for gallstone-related obstruction.
• Spleen Enlargement: Measuring spleen size is important for blood diseases or infection. Ultrasound quickly shows if it’s enlarged.
• Large Vessels: Detects abdominal aortic aneurysm, assesses vessel width, and uses Doppler for blood flow.

In the pelvic area, the uterus and ovaries are examined in women; in men, the prostate. Testes are also checked with scrotal ultrasound—for torsion, cysts, tumors, or fluid accumulation. Thyroid ultrasound is common for nodules, cysts, or inflammation, and Doppler can give clues about blood flow and risk level.

What Happens During an Ultrasound Procedure?

During your ultrasound appointment, you’ll usually be asked to lie comfortably on a bed and expose the area to be examined. For abdominal ultrasound, your upper abdomen will be uncovered. A clear, slippery gel is applied to the skin—this eliminates air between the probe and skin, which could block sound transmission.

The transducer (probe) is gently moved over the gel, creating real-time images on the screen. The doctor or technician may press at different angles to view organs like the liver, kidneys, or gallbladder. You may feel some pressure but generally no pain. The gel might feel cold, but there’s usually no significant discomfort.

For pelvic ultrasound, a full bladder may be required for clearer views. Sometimes, transvaginal ultrasound is performed using a slim probe for early pregnancy or closer examination of the reproductive organs.

The procedure usually lasts 15–30 minutes, depending on the area and detail required. Since no anesthesia or injection is involved, you can return to normal activities immediately. Disposable towels are provided to wipe off the gel, and you may receive preliminary results right away or after some reporting time, depending on the center.

Why Choose Ultrasound Over Other Imaging Techniques?

• No Radiation: X-ray and CT use ionizing radiation, which can be a concern for pregnant women or those wishing to avoid radiation. Ultrasound only uses sound waves, so there is zero radiation risk.
• Real-Time Imaging: CT and MRI provide sectional images at one point in time; ultrasound offers a “live broadcast,” making it ideal for observing organ movement or blood flow (heart valves, vessels, fetal motion, etc.).
• Low Cost and Easy Access: Ultrasound machines are generally less expensive and portable, making them useful in emergency rooms, intensive care units, or mobile health services in remote areas.
• Quick Application: Especially in emergencies, ultrasound can provide a rapid bedside assessment (POCUS—Point of Care Ultrasound), unlike CT or MRI, which require patient transport and setup.
• Soft Tissue and Fluid Detection: Ultrasound quickly distinguishes whether a mass is solid or fluid-filled—important for differentiating cysts from tumors. Drainage of cystic fluid or abscesses can also be performed under ultrasound guidance.
• Pregnancy and Pediatrics: The absence of radiation makes it unrivaled for pregnant women and children. Additionally, patients with claustrophobia or metal implants (which can preclude MRI) may prefer ultrasound.

Which Abdominal Diseases Can Be Diagnosed by Ultrasound?

• Gallstones and Cholecystitis: Shows gallstones, whether they have moved into a duct, wall thickening, and fluid around the gallbladder—helpful for acute upper right abdominal pain.
• Liver Diseases: Detects liver enlargement, masses, cysts, hemangiomas, and signs of fatty liver or cirrhosis. It is a key follow-up tool for chronic liver diseases.
• Kidney Stones and Urinary Problems: Identifies stones, kidney size, urinary tract dilation or blockage. While very small or hidden stones may be missed, it is sufficient for diagnosis in most cases.
• Appendicitis: For suspected lower right abdominal pain, ultrasound checks for appendix thickening or fluid. It is preferred over CT for children and young patients.
• Pancreatitis: Acute pancreatitis may show as an enlarged pancreas or surrounding fluid. Gallstones as the cause (choledocholithiasis) can also be investigated.
• Spleen Enlargement or Injury: Shows enlargement or rupture due to blood disorders or trauma.
• Aortic Aneurysm: Especially in older patients, detects dangerous widening of the abdominal aorta—fast and easy screening.

Frequently Asked Questions

Can ultrasound detect cancer?
Ultrasound can detect masses in organs like the thyroid, breast, liver, or kidney, and provide clues about their benign or malignant nature. However, it is not usually sufficient for a definitive cancer diagnosis; suspicious cases often require biopsy or further tests.

What can be seen in an abdominal ultrasound?
Liver, gallbladder, spleen, pancreas, kidneys, bladder, and main vessels are commonly evaluated. Information is gathered about stones, cysts, tumors, enlargement, or inflammation. Uterus and ovaries in women, and prostate in men, can also be assessed.

What is the difference between CT and ultrasound?
CT (computed tomography) uses X-rays for sectional imaging and involves radiation. Ultrasound uses sound waves with no radiation. CT is better for bone and lungs; ultrasound is better for soft tissues, fluids, and blood flow. CT offers more detailed sections, while ultrasound is real-time.

Can inflammation be seen on ultrasound?
Yes, ultrasound is effective for detecting many inflammatory conditions. For example, appendicitis, cholecystitis, kidney infection, or abdominal abscesses can be seen. Fluid buildup, organ wall thickening, or abscess formation are evaluated.

What diseases can be diagnosed with abdominal ultrasound?
Fatty liver, gallstones, cholecystitis, kidney stones or cysts, splenomegaly, pancreatitis, intra-abdominal fluid (ascites), some tumors and abscesses can all be detected. The size, structure, and blood flow of organs are assessed.

What types of ultrasound are there?
There are many types: standard 2D ultrasound is most common; others include 3D/4D ultrasound (for fetal imaging), Color Doppler (for blood flow), abdominal, pelvic/transvaginal (gynecology), cardiac (echocardiography), breast, and thyroid ultrasounds.

What should be done before having an ultrasound?
Preparation depends on the type. For abdominal ultrasound, 8–12 hours of fasting is usually required. For pelvic ultrasound, a full bladder is needed (drink water, don’t urinate). Breast or thyroid ultrasound generally require no special preparation. Check with your appointment center for the exact requirements.

Prof. Dr. Özgür KILIÇKESMEZ

Girişimsel Radyoloji ve Nöroradyoloji Uzmanı Prof. Dr. Özgür Kılıçkesmez, 1997 yılında Cerrahpaşa Tıp Fakültesi’nden mezun oldu. Uzmanlık eğitimini İstanbul Eğitim ve Araştırma Hastanesi’nde tamamladı. Londra’da girişimsel radyoloji ve onkoloji alanında eğitim aldı. İstanbul Çam ve Sakura Şehir Hastanesi’nde girişimsel radyoloji bölümünü kurdu ve 2020 yılında profesör oldu. Çok sayıda uluslararası ödül ve sertifikaya sahip olan Kılıçkesmez’in 150’den fazla bilimsel yayını bulunmakta ve 1500’den fazla atıf almıştır. Halen Medicana Ataköy Hastanesi’nde görev yapmaktadır.