[Urodynamic studies of the upper urinary tract. I. Introduction and diagnosis of the obstruction]

Present experience precludes any assertion as to what a urodynamic exploration of the upper urinary tract exactly comprises, and what the fundamental indications are, despite the many attempts already made, which the author recalls. After establishing the conceptual difference between obstruction and stasis, the author goes on to analyze the existing methods for identifying the existence of an obstruction in cases of chronic dilatation. Noninvasive methods, intravenous urography, diuretic urography, conventional and diuretic renography and analysis of the parenchymal transit time, are all probably successful in establishing the existence of an obstruction in 85 per cent of cases of chronic dilatation of the upper urinary tract; but these methods cannot be used to quantify the obstruction, or even identify it in certain specific cases. In order to quantify the obstruction, recourse must be had to invasive methods, and more particularly, in view of the limitations of basal and diuretic pyelomanometry, to combined pressure/flow studies. The author analyzes the two possibilities open for the application of these procedures (constant flow perfusion, or perfusion with a constant pressure) together with their advantages and drawbacks.