Diuretic Renography

Another confirmatory test, used extensively in the office setting to confirm the diagnosis of upper urinary obstruction but rarely in the emergency room setting, is diuretic renography. Like EXU, diuretic renography is a dynamic test providing functional data for the kidneys. Not only can diuretic renography help with the diagnosis of obstruction, the test can also provide data on split renal function. In contrast to EXU, diuretic re-

nography is associated with minimal risk of contrast-related side effects (i.e., allergic reactions are unlikely), minimal risk of contrast-related nephrotoxicity, and can be performed with a lower amount of radiation exposure. The most commonly used radiotracer for diuretic renography is technetium 99m mercaptoacetyl-triglycine (99mTc-MAG3). When information regarding renal function is preferentially required, the favored radiotracer is dimercaptosuccinic acid (DMSA). Because DMSA accumulates in the kidneys over a period of several hours, the role of this test is limited in the urgent evaluation and management of upper urinary tract obstruction (Croft et al. 1996). Before the introduction of diuretic renography, the Whitaker test was routinely used to confirm the diagnosis of upper urinary tract obstruction. In the urgent evaluation of apatient with presumed upper urinary tract obstruction nowadays, the role for this test is even less j ustified than that of diuretic renography.

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