A trial of the value of diuresis renography in equivocal upper urinary tract obstruction is presented. Fifty-two patients were examined by standard renography and renography under a diuretic provocation. The results indicate that the technique is of considerable value in making the vital distinction between dilatation on the excretion urogram due to atonicity and that caused by a genuine obstruction. A quantitative index of the response to diuresis reflecting the degree of impedance to flow is described--the Diuresis Excretion Index. Diuresis renography is recommended in the evaluation of the patient with equivocal urinary tract obstruction.

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Thirty-five hydronephrotic kidneys, in which diuresis renography showed either an equivocal (13) or non-obstructive (22) response pattern, were studied by a modified method in which intravenous frusemide was given 15 min before the start of the renogram so as to assess elimination during the period of maximum diuresis. Thirteen kidneys were identified as obstructed, including three in which the standard diuretic renogram appeared to exclude obstruction. These results indicate that the modified method increases the specificity of diuresis renography when used to assess patients with equivocal pelviureteric junction obstruction.

The results of a combined study of 25 patients with idiopathic hydronephrosis are presented. Diuresis renography was performed pre-operatively and surgically removed specimens of the renal pelvis and ureter were examined by light and electron microscopy. There was good correlation between the results of these 2 methods of assessment which have defined 2 broad categories of patients with renal pelvic dilatation. These findings are discussed with particular reference to the clinical value of diuresis renography.