Intravenous pyelogram  An intravenous pyelogram (IVP), also called an intravenous urogram (IVU), is a radiological procedure used to visualize abnormalities of the urinary system, including the kidneys, ureters, and bladder. Unlike a kidneys, ureters, and bladder x-ray (KUB), which is a plain (that is, noncontrast) radiograph, an IVP uses contrast to highlight the urinary tract. In IVP, the contrast agent is given intravenously, allowed to be cleared by the kidneys and excreted through the urinary tract as part of the urine. If this is contraindicated for some reason, a retrograde pyelogram, with the contrast flowing upstream, can be done instead. The technique of IVP was originally developed by Leonard Rowntree of the Mayo Clinic in the 1920s. IVP was previously the test of choice for diagnosing ureter obstruction secondary to urolithiasis but in the late 1990s non-contrast computerized tomography of the abdomen and pelvis replaced it because of its increased specificity regarding etiologies of obstruction. An injection of X-ray contrast medium is given to a patient via a needle or cannula into the vein, typically in the antecubital fossa of arm. The contrast is "excreted" or removed from the bloodstream via the kidneys, and the contrast media becomes visible on X-rays almost immediately after injection. X-rays are taken at specific time intervals to capture the contrast as it travels through the different parts of the urinary system. This gives a comprehensive view of the patient's anatomy and some information on the functioning of the renal system. Immediately after the contrast is administered, it appears on an X-ray as a 'renal blush'. This is the contrast being filtered through the cortex. At an interval of 3 minutes, the renal blush is still evident (to a lesser extent) but the calyces and renal pelvis are now visible. At 9 to 13 minutes the contrast begins to empty into the ureters and travel to the bladder which has now begun to fill. To visualize the bladder correctly, a post micturition X-ray is taken, so that the bulk of the contrast (which can mask a pathology) is emptied. An IVP can be performed in either emergency or routine circumstances. This procedure is carried out on patients who present to an Emergency department, usually with severe renal colic and a positive hematuria test.