Kidney Ultrasound: What It Shows, Why It’s Done, and What to Expect

At Independent Physicians Medical Center (IPMC) in Northeast Philadelphia, we offer kidney ultrasound imaging in our comfortable outpatient facility with experienced sonographers and board-certified radiologists.

What Is a Kidney Ultrasound?

A kidney ultrasound — also called a renal ultrasound — uses sound waves to create real-time images of the kidneys, ureters (the tubes that connect the kidneys to the bladder), and bladder. It shows the size, shape, position, and internal structure of each kidney, including the cortex (outer tissue), medulla (inner tissue), collecting system (where urine collects), and the surrounding fat and tissue.

Kidney ultrasound also includes Doppler imaging when blood flow assessment is needed, such as when evaluating for renal artery stenosis or monitoring a kidney transplant.

Why Would Your Doctor Order a Kidney Ultrasound?

Your physician may recommend a kidney ultrasound to evaluate:

• Kidney stones — while CT is the gold standard for stone detection, ultrasound can identify many stones (especially larger ones) without radiation exposure and is often used as the first test in children, pregnant women, and patients who need to limit radiation
• Hydronephrosis — swelling of the kidney caused by a backup of urine, which may result from stones, tumors, strictures, or other obstructions. Ultrasound is the best initial test for detecting hydronephrosis
• Kidney cysts — fluid-filled sacs that are extremely common, especially with aging. Ultrasound classifies cysts using the Bosniak classification system to determine whether they are simple (benign), complex, or concerning
• Kidney tumors or masses — ultrasound can detect solid masses in the kidney that may require further evaluation with CT or MRI
• Abnormal kidney function test results — when blood tests show elevated creatinine or reduced GFR (glomerular filtration rate), ultrasound helps identify structural causes
• Blood in the urine (hematuria) — to check for stones, tumors, cysts, or other sources of bleeding
• Recurrent urinary tract infections — evaluating for anatomical abnormalities or retained fluid that predisposes to infection
• Kidney size assessment — small kidneys may indicate chronic kidney disease, while enlarged kidneys may suggest obstruction, inflammation, or other conditions
• Polycystic kidney disease — a genetic condition causing multiple cysts in the kidneys
• Kidney transplant evaluation — before and after transplant to assess the donor kidney and monitor the transplanted kidney
• Pediatric kidney evaluation — ultrasound is the preferred imaging test for children because it uses no radiation

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How to Prepare and What to Expect

For a kidney ultrasound, you may be asked to drink water before the exam to fill your bladder, which provides a better acoustic window to the kidneys and allows the bladder to be evaluated as well. You can usually eat and take medications normally.

At IPMC, you’ll lie on an exam table. The sonographer will apply gel to your abdomen and flanks (sides of your back) and move a transducer over these areas. You may be asked to roll onto your side or take deep breaths to improve visualization. Both kidneys are always imaged for comparison. The exam typically takes 20 to 30 minutes and is painless.

After the exam, there is no recovery time. A board-certified radiologist will review the images and send a report to your doctor, who will discuss the results and any recommended follow-up.