A kidney ultrasound is a non-invasive medical imaging technique that uses high-frequency sound waves to create detailed pictures of the kidneys and surrounding structures. It is a widely used, safe method for examining the urinary system because it does not involve radiation exposure. The sound waves bounce off internal organs and tissues, generating echoes that a computer then translates into real-time images for analysis.
Why a Kidney Ultrasound is Performed
Healthcare providers often recommend a kidney ultrasound to investigate symptoms like unexplained back or flank pain. The procedure is also frequently performed when blood is detected in the urine, a condition known as hematuria. Suspected kidney stones are another frequent indication, as the ultrasound can help locate these mineral deposits.
A kidney ultrasound can assess kidney function, particularly in cases of elevated creatinine levels, which may signal impaired kidney activity. It is also used to monitor known kidney conditions, such as chronic kidney disease, or to check for blockages in the urinary tract, like those caused by an obstruction in the ureters. Additionally, the test helps evaluate kidney infections, cysts, tumors, or signs of injury to the kidneys.
Preparing for and Undergoing the Procedure
Preparing for a kidney ultrasound may require fasting for a few hours, particularly if assessing blood flow to the renal arteries, though it is not always necessary for a standard kidney ultrasound. Patients are often asked to drink a specific amount of water before the appointment to ensure their bladder is full, which helps in visualizing the bladder and surrounding areas. Wearing comfortable, loose-fitting clothing is advisable, and patients may be asked to remove jewelry or change into a gown.
During the procedure, the patient lies on an examination table. A clear, water-based gel is applied to the skin over the kidney area, which helps the transducer make secure contact and allows sound waves to travel effectively into the body. The sonographer then gently moves a handheld device called a transducer over the skin. The sound waves emitted by the transducer create echoes that are converted into images on a monitor, and the procedure is generally painless, lasting typically between 20 to 30 minutes.
What a Kidney Ultrasound Can Reveal
A kidney ultrasound can clearly show the presence and characteristics of kidney stones, appearing as bright spots with a shadow behind them, and can indicate their size and location. The procedure is also effective in identifying kidney cysts, which are typically fluid-filled sacs that can be simple or more complex, and tumors, distinguishing between solid masses and fluid-filled ones.
The ultrasound can detect hydronephrosis, which is swelling of the kidney due to urine backup, often caused by an obstruction in the urinary tract. It also reveals changes in kidney size or shape; normal adult kidneys typically measure around 9-13 centimeters in length, 4-6 centimeters in width, and 3-5 centimeters in thickness. Additionally, the ultrasound can identify fluid collections around the kidneys, abscesses, and assess blood flow through the renal arteries and veins.