[Importance of MRI in hydronephrosis caused by acute or chronic ureteral obstruct. Prospective study].

Magnetic resonance imaging (MRI) of the normal kidney shows in T1 weighted sequence a spontaneous corticomedullary differentiation. In case of ureteral obstruction the corticomedullary differentiation tends to disappear, the medullary signal intensity in T1 weighted sequence is lower and the whole kidney signal intensity in T2 weighted sequence is greater in acute phase. 16 patients with lithiasis ureteral obstruction were evaluated in MRI study. A T1 weighted S.E. 500/28 sequence in axial and frontal planes (7 mm thick-section) and a T2 weighted E.G. 2000/40 sequence in axial plane were used to study the hydronephrotic kidney and to compare it with contralateral normal kidney. Ultrasounds and intravenous pyelography (IVP) were performed to assess the renal dysfunction. MRI realize a morphologic study of the kidney which can be compared with ultrasounds and IVP. MRI assess renal function by the signal intensity but the time of obstruction and the time of medical treatment before MRI are of interest.