A kidney ultrasound is a non-invasive imaging test that provides visual information about the kidneys and surrounding structures. This procedure uses sound waves to create real-time images, distinguishing it from imaging techniques that use radiation. It is a common and safe method for healthcare providers to assess kidney health and diagnose various conditions.
How Kidney Ultrasound Works
Ultrasound technology emits high-frequency sound waves, similar to sonar. A small handheld device called a transducer is placed on the skin, sending these sound waves into the body. As they encounter organs and tissues, they bounce back as echoes to the transducer. A computer processes these echoes, converting them into live images displayed on a monitor. The gel applied to the skin helps ensure proper transmission of the sound waves and eliminates air pockets that could interfere with image quality.
Key Findings from a Kidney Ultrasound
A kidney ultrasound can reveal a range of conditions by visualizing the kidneys’ internal structures and surrounding areas. This diagnostic tool helps identify abnormalities that may indicate underlying health issues.
Kidney Stones
Kidney stones are solid masses that can form within the kidneys. On an ultrasound, these stones typically appear as bright, reflective spots, often accompanied by a “posterior acoustic shadow” (a dark area behind the stone where sound waves cannot pass). The ultrasound can determine their size and location, and also show if they are causing a backup of urine, a condition called hydronephrosis.
Cysts and Tumors
Kidney ultrasounds can differentiate between simple cysts and more complex masses. Simple cysts are common, benign, fluid-filled sacs that appear as round or oval, thin-walled structures with clear, anechoic (black) contents. More complex cysts or solid masses, which may indicate tumors, often have irregular shapes, thicker walls, internal echoes, or solid components, requiring further investigation.
Hydronephrosis (Kidney Swelling)
Hydronephrosis is kidney swelling due to urine buildup, often caused by an obstruction in the urinary tract. On ultrasound, this appears as an enlarged, fluid-filled collecting system within the kidney, seen as branching, interconnected areas of decreased echogenicity. The severity of hydronephrosis can be graded based on the extent of dilation of the renal pelvis and calyces.
Kidney Size, Shape, and Position
The ultrasound assesses kidney dimensions, overall structure, and placement within the abdomen. A normal adult kidney typically measures 10-12 cm in length, though this varies with age and body size. Abnormalities in size, shape, or position can suggest chronic kidney disease, congenital anomalies, or injury.
Blood Flow Issues (using Doppler ultrasound)
Doppler ultrasound measures the speed and direction of blood flow within the renal arteries and veins. This is useful for identifying conditions like renal artery stenosis, where artery narrowing reduces blood supply to the kidneys. Changes in blood flow patterns and velocities can indicate blockages or other vascular issues affecting kidney function.
Abscesses or Infections
Ultrasound can identify fluid collections or signs of inflammation within or around the kidney, indicating an abscess or infection. A renal abscess typically appears as a well-defined area less echogenic (darker) than surrounding tissue, sometimes with internal echoes. While ultrasound can suggest an infection, additional tests are often needed for a definitive diagnosis.
What to Expect During a Kidney Ultrasound
Patients typically lie on an examination table, often on their back, though they may be asked to turn to their side for better imaging. A water-based gel is applied to the skin over the abdomen and flank area for good contact between the transducer and skin. The sonographer or radiologist moves the transducer gently across the skin, capturing images of the kidneys and bladder. You might be asked to hold your breath briefly or change positions for clearer views. The procedure is non-invasive and usually takes about 20 to 30 minutes.
Interpreting Your Kidney Ultrasound Results
After your kidney ultrasound is complete, a radiologist will analyze the images. The radiologist then creates a detailed report outlining the findings, which is sent to the healthcare provider who requested the ultrasound. Your referring doctor will discuss the results with you, explaining what the findings mean for your health. The ultrasound results might confirm a diagnosis, rule out a suspected condition, or indicate the need for further diagnostic tests, such as blood work, urine tests, or other imaging studies like a CT scan.