A urinary tract ultrasound (UT US) is a non-invasive medical imaging test that uses high-frequency sound waves to create real-time pictures of the internal structures within the urinary system. This procedure allows healthcare providers to visualize the kidneys, the bladder, and the tubes connecting them, known as the ureters. The scanner generates detailed, cross-sectional images by emitting sound waves that travel through tissue and reflect off various densities. The process offers a safe and widely available method for diagnostic assessment without using ionizing radiation.
Identifying the Need for the Procedure
Physicians frequently order a urinary tract ultrasound when a patient reports unexplained flank or abdominal pain suggesting a kidney problem. The technology is also used to investigate persistent, recurring urinary tract infections (UTIs) that do not respond to standard treatment protocols, or the presence of blood in the urine (hematuria).
The UT US is highly effective at detecting dense calcifications, such as kidney stones (nephrolithiasis), and can accurately measure their size and location. The scan also assesses for conditions like hydronephrosis, which is the swelling of the kidney due to a backup of urine caused by a blockage in the ureter. Evaluating the overall size, shape, and position of the kidneys and bladder helps the clinician assess functional health and screen for structural abnormalities.
Essential Preparation Guidelines
Adequate preparation is necessary to ensure the ultrasound technician can obtain clear, diagnostic images of the urinary tract structures. The most important instruction for a urinary tract ultrasound is arriving at the clinic with a full bladder. A distended bladder pushes the air-filled bowel loops out of the way and acts as an acoustic window, allowing sound waves to pass through easily and provide a clear view of the bladder walls and the lower ureters. To achieve this, patients are typically instructed to finish drinking 32 ounces (about 1 liter) of water or clear liquid approximately one hour before the scheduled appointment time. The patient must not empty their bladder after drinking the fluid until the technician gives permission to void.
In certain cases, a period of fasting for six to eight hours before the scan may be requested, particularly when the physician needs a clearer view of the upper poles of the kidneys. This fast minimizes gas in the intestines, which can scatter the sound waves and obscure the view of the deeper kidney structures. Always confirm the specific preparation instructions provided by the ordering physician or the imaging center.
What Happens During the Scan
Upon arrival at the imaging center, the patient will check in and may be asked to change into a medical gown. The patient is then asked to lie flat on their back on an examination table. The initial imaging often focuses on the bladder while it is fully distended.
The technologist, known as a sonographer, will apply a small amount of warm, water-soluble gel directly onto the skin of the lower abdomen and sometimes the flanks and back. This gel eliminates air pockets between the skin and the transducer, ensuring optimal transmission of the sound waves into the body and reception of the echoes. The sonographer then takes a hand-held device called a transducer and gently presses it against the skin. They will systematically move the transducer across the abdomen to visualize the bladder, and then move to the flanks and back to visualize the kidneys, sometimes asking the patient to roll slightly onto their side.
While the procedure is generally painless, the patient may feel some pressure as the sonographer pushes the transducer to obtain clear images, especially when trying to assess structures deep within the abdomen. A unique part of the urinary tract ultrasound is the pre- and post-void imaging. After the initial images are captured with a full bladder, the patient is asked to completely empty their bladder in a nearby restroom. The sonographer then repeats a quick scan to measure the remaining volume of urine, known as the post-void residual. This measurement helps evaluate the bladder’s muscle function and emptying efficiency. The entire scanning process, including the time taken to void, typically takes between 20 and 45 minutes.
Receiving and Interpreting the Results
Once the images are captured by the sonographer, they do not provide immediate results; their role is solely to acquire the best possible data set for the physician. The ultrasound images are then sent digitally to a specialized physician, known as a radiologist, who interprets these visual data sets. The radiologist analyzes the images for any signs of stones, masses, hydronephrosis, or abnormalities in the organ structure and size. The radiologist then generates a formal report that outlines all findings and provides a diagnostic impression.
This report is then transmitted to the ordering physician, which is typically the patient’s primary care doctor or a urologist. The timeline for receiving these results can vary based on the facility and the urgency of the findings, often taking anywhere from 24 hours to several business days. The patient should schedule a follow-up appointment with the referring physician to discuss the contents of the report. This physician is best equipped to explain what the findings mean in the context of the patient’s overall health history and to recommend any subsequent steps, such as treatment plans or further diagnostic testing.