Ultrasound of the Kidneys

Ultrasound of the kidneys is a common test done to look at the structure of the kidneys.  An advantage of ultrasound is that there is no radiation.  Ultrasound uses sound waves to produce images of the body.  A technologist does an ultrasound test with a hand held probe.  A radiologist produces a report based on the images.

Why is ultrasound of the kidneys done?

Ultrasound of the kidneys is done to evaluate the kidneys when the kidneys are not functioning well.  The test is also done to look for a cause of symptoms referable to the kidneys.  Often kidney abnormalities produce flank pain or lab abnormalities like blood in the urine.


Kidney ultrasound is often done to look for stones.  Kidney stones look like focal bright areas with what we call shadowing.  Shadowing is when there is a darkness underneath the bright area.  Kidney stones can produce symptoms, especially when they pass into the ureters and block the kidney.


Hydronephrosis is when the kidney collecting system becomes dilated.  This is the part of the kidney that collects urine before it goes into the ureter and bladder.  This area swells as urine backs up.  This is easily detected on ultrasound.  This is most common from a stone blocking the ureter.  It can also happen from other blockages like tumors, blood clots and area of narrowing.

Cysts and masses

Ultrasound is good at detecting cysts and masses.  Cysts are benign and filled with fluid.  Some more complex cysts can be more concerning and represent neoplasms.  Ultrasound is also good at identifying solid masses which can represent cancer.  Some masses identified need further evaluation with CT or MRI for further diagnosis.

Structural abnormalities

Ultrasound is good at identifying structural abnormalities.  These things can include horseshoe kidneys and other abnormalities you are born with.  Horseshoe kidneys occur when the two kidneys are joined together in the midline.  Ultrasound is good at telling us the size and shape of the kidneys.  Ultrasound can tell us if there is scarring, prior tissue loss or lobulations which can be normal.

Ultrasound of the kidneys is a good test to begin a workup for kidney abnormalities.  It can tell us when there are stones, blockages, cysts and masses.   Kidney ultrasound is relatively inexpensive, does not use radiation,  and is fairly quick.  The test does depend on the skill of the technologist.  At times, we need further testing to evaluate an abnormality.




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