[Urinary obstruction: different radio-clinical types]

Urinary obstruction has three different clinical aspects: acute, chronic and intermittent. Imaging modalities and diagnostic strategies are different for each of them. Although the morphologic analysis is accurate for all imaging modalities, the diagnosis of hydronephrosis may not be so easy, except for major typical form. There are some pitfalls, for instance the presence of parapelvic cysts at ultrasound and difficulties for initial or minor forms. Nowadays, IVU is still in routine the best examination to assess renal function. In the near future, MRI should be able to give useful information for both morphologic and functional status and take an important role in the evaluation of urinary obstruction.