Solid masses of the kidney are often discovered on CT incidentally or after another type of imaging exam identifies a mass which needs to be further evaluated. A CT of the kidneys and urinary tract may also be ordered after your doctor discovers blood in your urine.
A mass of the kidney needs a CT without contrast and one in which contrast is placed into your vein for complete evaluation. This is done one after the other in one session. The idea is that a solid or cancerous mass will take up the contrast and enhance or become brighter after the contrast is administered. Solid tissues need blood to be fed and contrast goes where blood goes. Cysts or water filled masses don’t need blood to feed the contents so they stay the same after contrast is administered.
Solid masses of the kidney are concerning for cancer and will often be removed. Simple cysts will be left alone. Some more complex cysts will also be removed and contrast helps with their evaluation as well. The distinction between solid and cystic masses of the kidney is therefore of most importance.
Solid masses are often renal cell carcinomas or cancers of the kidney. They can also be cancers of the collecting system where urine is collected. These are called transitional cell cancers. Solid masses can also be benign, but can not always be diagnosed before surgery. One example is an oncocytoma which can look like a renal cell cancer. Another is an angiomyolipoma which often has fatty tissue but not always.
Once a solid mass is diagnosed the radiologist will see if it has spread. Tumors of the kidney can spread into the vein of the kidney and inferior vena cava. Tumors can also spread to lymph nodes, bones, and organs such as the liver. This is important to identify as the treatment will often change.
Referral to a urology doctor will be needed for surgery. He will determine whether your entire kidney or part of it needs to be removed. If the tumor has spread, then an oncologist will be needed for chemotherapy treatment. Often patients will get follow up imaging after surgery to make sure the tumor hasn’t come back or spread. Follow up imaging is also done for patients who’s tumor has spread to see how they are responding to treatment.