While intravenous urography (IVU) was considered the gold standard of radiological workup for urinary li-thiasis, its utility has greatly diminished since the advent of unenhanced helical CT. It is superior to ultrasound in diagnosis but IVU requires an injection of contrast solution and leads to a low but not inconsiderable dose of radiation, especially during the first trimester. Different examination protocols have been proposed aiming to limit the radiation exposure as much as possible to three or four radiographs: plain abdomen, 30 s, 20 min (McAleer and Loughlin 2004; Sto-thers and Lee 1992) plus or minus one late x-ray (Dore 2004); plain abdomen, 20 min, late x-ray (Klein 1984). It is important to use high-sensitivity films, reduce the aperture as much as possible, have large radiology rooms available, choose digital radiology, and use a lead apron for the side of the healthy kidney (Biyani and Joyce 2002a; McAleer and Loughlin 2004). Given bony superposition and the voluminous uterus, identifying small stones is sometimes difficult (Biyani and Joyce 2002a; Dore 2004; Evans and Wollin 2001). The exam does not always differentiate physiological and pathological dilatations (Biyani and Joyce 2002a; Evans and Wollin 2001).
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