• CT with intravenous dye (the same dye used for intravenous pyelograms) will accurately diagnose renal
  tumors in 95 percent of cases and be falsely positive in fewer than 2 percent. This test may also show the
  tumor extension outside the kidney and can determine the extent of lymph node, liver and blood vessel
  involvement.
• MRI has replaced the inferior vena cavagram for determining more clearly the extent of blood vessel
  involvement and involvement of adjacent structures.
• Selective renal arteriography is helpful in finding small tumors and providing information that sometimes may
  be needed at the time of surgery about uncommon blood vessel patterns and, in selected cases, determining the
  possibility of a partial nephrectomy (removal of only a portion of the kidney) for small localized tumors.
• Other tests before surgery simply assure that there are no distant metastases. These include chest x-rays (if
  abnormal it may be followed by a chest CT scan), bone scans or skeletal x-rays and a liver scan (unnecessary
  when an abdominal CT scan is performed).

Biopsy 
• Ultimately, the diagnosis is made either by removing the kidney (nephrectomy) or by a thin needle aspiration
  through the skin for cytologic slide examination. Looking for tumor cells in the urine is not useful.