Ultrasound, or sonography, is an imaging technique that utilizes high-frequency sound waves to create real-time pictures of internal body structures. This non-invasive method involves a transducer placed on the skin, which transmits sound waves into the body and records the returning echoes. The signals are processed by a computer to form an image of organs and tissues. Ultrasound provides visualization of soft tissues without exposing the patient to ionizing radiation, making it a first-line diagnostic tool for many conditions.
Detection in Abdominal and Urinary Systems
Ultrasound provides clear visualization of solid organs and fluid-filled structures throughout the abdomen, often serving as the initial diagnostic step for unexplained pain. The liver is routinely assessed, with the technology identifying diffuse conditions like fatty liver disease, which appears as a brighter (hyperechoic) texture compared to normal tissue. It can also detect focal masses, cysts, or signs of advanced scarring, such as the lumpy, shrunken appearance of a cirrhotic liver.
Ultrasound is the preferred method for diagnosing gallstones (cholelithiasis). These stones appear as bright, echogenic foci that cast a posterior acoustic shadow, and their mobility can be confirmed by changing the patient’s position. Inflammation of the gallbladder, or cholecystitis, is diagnosed by observing gallstones combined with secondary signs like thickening of the gallbladder wall and fluid accumulation.
In the urinary tract, sonography is the primary tool for identifying kidney stones (nephrolithiasis), which are seen as bright spots with acoustic shadowing. It is also used to diagnose hydronephrosis, appearing as a dilated renal pelvis and calyces. The scan can also characterize kidney cysts, distinguish them from solid tumors, and assess for abnormalities within the bladder, such as stones or masses on the bladder wall.
Identifying Vascular and Circulatory Conditions
A specialized application called Doppler ultrasound assesses the circulatory system by visualizing the movement, speed, and direction of blood flow. This technique combines a standard structural image (B-mode) with a functional component that measures changes in the frequency of sound waves reflected by moving red blood cells. This allows for the detection of obstructions or abnormal flow patterns within both arteries and veins.
For veins, Doppler ultrasound is the initial imaging modality for diagnosing Deep Vein Thrombosis (DVT). The clot is identified by the failure of the vein to fully compress under pressure from the transducer and the absence of blood flow on the color map. Doppler can also assess chronic venous insufficiency by detecting blood flowing backward (reflux).
In the arterial system, Doppler technology helps identify narrowing (stenosis) or blockages caused by plaque buildup, which can restrict blood supply to organs or limbs. It is used in screening for abdominal aortic aneurysm (AAA) by measuring its diameter. The analysis of the arterial waveform and flow velocities helps determine the severity of the arterial disease.
Diagnosing Reproductive and Pelvic Disorders
Ultrasound, frequently performed using a high-resolution transvaginal approach, is the first-line method for evaluating the female reproductive organs and diagnosing numerous pelvic conditions. A common finding is Polycystic Ovary Syndrome (PCOS), characterized by enlarged ovaries containing an increased number of small follicles, often described as having a “string of pearls” appearance. The central ovarian tissue (stroma) may also appear brighter (hyperechoic) than normal.
The technique is crucial in the assessment of pregnancy complications, particularly suspected ectopic pregnancy. Findings suggestive of this condition include an empty uterus combined with the presence of an abnormal adnexal mass (“blob sign” or “bagel sign”) and sometimes free fluid in the pelvis. For Pelvic Inflammatory Disease (PID), ultrasound can identify complications such as thickened, fluid-filled fallopian tubes (hydrosalpinx) or a tubo-ovarian abscess, often showing increased blood flow (hyperemia).
In the uterus, ultrasound is highly accurate for locating and measuring uterine fibroids (leiomyomas), which appear as solid, well-defined masses within the wall of the uterus. For male health, transrectal ultrasound is used to evaluate the prostate in cases of Benign Prostatic Hyperplasia (BPH). In the testes, color Doppler ultrasound is the definitive test for diagnosing testicular torsion by demonstrating absent or significantly reduced blood flow in the affected testicle.
Assessing Superficial Structures and Soft Tissues
The relatively superficial location of certain structures makes them ideal for examination with high-frequency ultrasound probes. The thyroid gland is commonly evaluated for nodules, and ultrasound can distinguish between solid masses and fluid-filled cysts, and identify features that suggest a higher likelihood of malignancy. This imaging is also used to precisely guide a needle for biopsy of suspicious nodules.
In the musculoskeletal system, ultrasound evaluates soft tissue injuries, such as tears in tendons and ligaments. It can differentiate between partial- and full-thickness tears in the rotator cuff of the shoulder and assess the extent of damage. Inflammation of the fluid-filled sacs near joints, known as bursitis, is identified by an enlarged bursa containing excess fluid and thickening of the sac’s wall.
For breast health, ultrasound serves as an important complement to mammography, especially in women with dense breast tissue. It is used to characterize masses as either simple cysts (fluid-filled) or solid tumors, utilizing the standardized Breast Imaging-Reporting and Data System (BI-RADS) lexicon. Features such as an irregular shape, non-parallel orientation, and spiculated margins are considered highly suggestive of malignancy, guiding the decision for further intervention like a biopsy.