Intrapelvic pressure and caliceal dilatation in the evaluation of intermittent hydronephrosis.

We investigated 10 patients with suspected unilateral hydronephrosis and normal or minimal widening of the calices or renal pelvis on routine urography by high rate perfusion of the renal pelvis and simultaneous intrapelvic pressure measurement. All affected kidneys had reduced renal function (26 +/- 7 ml. per minute per 1.73 body surface area) evaluated from total and separate glomerular filtration rate studies using 51chromium-ethylenediaminetetraacetic acid clearance technique and isotope renography. Four patients without signs of obstruction operated upon because of renal calculi were used as controls with separate glomerular filtration rates greater than 40 ml. per minute per 1.73 body surface area bilaterally. The drainage function of the renal pelvis was studied by diuresis renography, simultaneous intrapelvic pressure measurement and fluoroscopy during infusion of roentgen contrast medium at a constant rate of 10.5 ml. per minute. The caliceal dilatation was calculated from planimetrical measurement of defined calices. The intrapelvic pressure gradually increased in all kidneys to a maximum value varying from 25 to 81 cm. water (average 47 +/- 15). In the control kidneys the intrapelvic pressure varied from 10 to 18 cm. water (average 14 +/- 3). Significant dilatation of the caliceal system did not occur until intrapelvic pressure values above 25 cm. water were measured. Caliceal dilatation and maximal intrapelvic pressure were correlated significantly to each other at a correlation coefficient of 0.95. Intrapelvic pressure flow measurement with contrast medium and roentgen film exposure at the time of increased pressure proved to be a useful method to diagnose outflow obstruction. The test was of particular value in cases of clinically suspected intermittent hydronephrosis, giving more reliable information than conventional renography and diuretic urography. The test could be used even when the glomerular filtration rate was decreased, thereby providing information on the presence of obstruction in cases when conventional renography and diuresis urography sometimes fail.