[Acute and irreversible obstructions due to a known and well tolerated ureteropelvic junction syndrome].

Hydronephrosis secondary to ureteropelvic junction syndrome (UPJ), especially when it is accompanied by moderate dilatation of the proximal renal cavities tends to be stable with little risk to the kidney. However, there are certain exceptions to this general rule and the situation may very suddenly and almost always unpredictably progress towards complete obstruction of the UPJ with loss of function of the corresponding kidney. From a series of about 400 cases of hydronephrosis, 230 of which were operated, the authors analysed 13 cases of intermittent hydronephrosis, three of which suddenly progressed towards complete, irreversible obstruction of the UPJ. This dramatic outcome is difficult to predict, but it would appear to be wise to operate on cases of intermittent hydronephrosis, even when only moderate, especially when they are symptomatic, i.e. Painful. The authors believe that an episode of renal colic without stones constitutes an absolute indication for surgery.