While ultrasound helps your doctor see the kidneys, more tests are needed to confirm UPJ obstruction. To make a proper diagnosis, your urologist must see how well urine is produced and drained. There are several tests that can be done.
Blood samples and urine samples may be taken. The BUN (blood urea nitrogen) and creatinine tests find if the kidney is working well as it filters the blood.
An intravenous pyelogram (IVP) was often used in the past. In this test, a dye is injected into the bloodstream. An X-ray is used to see the kidneys remove the dye from the blood. As the dye passes through urine, your doctor can see if the kidney, renal pelvis and ureter look normal.
A nuclear renal scan is similar to an IVP but is more modern. This test uses radioactive material instead of dye. The material can be seen with a special camera. This test gives the doctor good information about how the kidney is working and how much blockage there is.
CT scans are sometimes used in the emergency room to find out why children are having severe pain. A CT scan can easily show the obstructed kidney if that is the cause of the pain. Magnetic resonance imaging (MRI) is also used to look at the kidneys, ureters and the bladder. But MRI is expensive and not used everywhere.
Siblings need screening for UPJ obstruction only if they show signs. There have been some cases in which several members of a family have UPJ obstruction, but the majority of cases are individual.