Ultrasound is an often used test to look at the kidneys and kidney masses. Ultrasound is very good at telling if a kidney mass is suspicious for cancer or if it’s simply a cyst filled with fluid. Ultrasound may be ordered after your doctor detects blood in the urine or after another test like a CT detects a kidney mass which needs to be further evaluated.
Ultrasound is performed by a specially trained technologist and interpreted by a radiology doctor. Ultrasound is painless and uses no radiation, instead using high frequency sound waves to form an image. Ultrasound is user dependent unlike other tests like CT. This means the results and quality of the test are dependent on the person doing it.
On ultrasound, a kidney mass that is solid and suspicious will not meet the criteria for a cyst or fluid filled mass. The internal contents may appear partially cystic or complex. There may sometimes be internal blood flow which cysts do not have. The larger the size, the easier the distinction is made between cysts and solid masses. Small less then 1 cm lesions may be difficult to characterize on ultrasound. The exam may also be limited in obese patients.
Once a suspicious solid or complex mass is identified, a CT or MRI will be requested by the radiologist to further evaluate in many cases. The radiologist wants to confirm that there is enhancement or solid components to the mass. A CT or MRI with and without contrast placed into your vein is done. The idea is that the contrast will make any solid areas appear brighter indicating that the mass is not simply a cyst. A cyst only has fluid inside so it should not enhance. Sometimes cysts are complex and may be followed. Other times, the enhancement may be minimal and the radiologist may request another imaging test to be more confident.
Solid masses will often be treated by surgical resection. A referral to a urologist will follow who will determine if the entire or part of the kidney needs to be removed. Ultrasound is therefore one of the imaging tests used to evaluate kidney masses. Sometimes ultrasound is the first test, and at other times, it’s used as another test to confirm findings on another test like CT.