Antegrade pyelography uses special contrast agent (dye) to produce detailed X-ray pictures of the upper urinary tract (kidney and ureter). It is commonly used to diagnose conditions including hydronephrosis, ureteropelvic junction (UPJ) obstruction and obstruction of the ureters.
This test is performed in a hospital radiology department or in a health care provider's office by a radiologist or X-ray technician. The kidneys will initially be examined with an ultrasound probe or a CT scan. After they are located, the overlying skin will be anesthetized and a needle will be passed directly into the kidney. This needle is used to inject dye to outline the renal collection system (part of the urinary tract draining urine between the kidney and bladder) on X-ray images and detect any blockages or obstructions.
While pyelography is considered generally safe, the major risk involves a reaction to the iodine-based dye. Minor reactions include hot flashes, nausea and vomiting. These are usually treated successfully with antihistamines, drugs that reduce the effects of the body's inflammatory compound, histamine. In very rare circumstances, more severe complications – breathing difficulties, low blood pressure, swelling of the mouth or throat and even cardiac arrest – can occur.
There is relatively low radiation exposure during this test. However, a patient who is or may be pregnant should notify their physician prior to this examination, as a fetus is susceptible to the risks associated with radiation.