Renography

A technique that uses a radioactive substance to measure kidney function. Renography is quick and painless and is used when obstruction of the passage of urine is suspected. The radioactive substance is injected into the bloodstream and passes through the kidneys into the urine. Radiation counts are taken continually throughout the procedure. Normally, the count rises and then falls as the substance passes into the bladder. If obstruction is present, the substance accumulates in the kidneys and the count continues to rise. (See also kidney imaging.)