[Urography: problems and errors in the diagnosis of renal masses]

New imaging modalities have gained a prominent role in both detection and diagnosis of kidney disorders. However, excretory urography (IVU) remains the screening examination of choice in everyday diagnostic routine, even though its value in characterising renal masses is poor. The search for more sensitive and less invasive diagnostic modalities has brought about some new dilemmas--e.g., which modality should be performed first when the clinical picture is suggestive of renal tumor, the presence of a malignancy with a negative IVU, small renal tumors as occasional findings--, and has enhanced previous problems,--e.g., technique, administration of i.v. contrast media. After defining the above problems, the authors discuss mistakes in the evaluation and interpretation of urograms. The problems are operator-dependent, or else they may be related to examination technique--e.g., inadequate preparation of the patient, poor image quality--, to the method of examination--e.g., inadequate injection of contrast agents (i.e., type, amount, method of injection)--, to kidney function and, finally, to lesion type. As for lesion type, errors can be related to the detection of the lesion itself--e.g., small renal masses (less than 3 cm phi)--and to lesion definition, due to atypical patterns or to difficult differentiation of tumors from normal findings, from anatomical variants or extrarenal structures.